Introduction

When disaster strikes, time is of the essence. Disaster responders, including medical personnel, who travel to respond to a disaster may not dedicate the same amount of time and diligence to personal preparation that they would for planned travel. Inadequate preparation and preventive measures, however, can result in illness or injuries and loss of mission effectiveness—even utilization of medical resources intended for disaster victims. The importance of pretravel health preparation before departing for a disaster response cannot be overstated ( Box 1.1 ). Many elements of pretravel health can be maintained over time, so that just-in-time measures can be implemented quickly.

This chapter will use a travel medicine framework, focusing on measures to prevent conditions and diseases that are associated with a change in physical and geographic environment. Travel medicine is dynamic, so it is important to use up-to-date resources to guide pretravel clinical decisions. This chapter will outline general considerations, but not attempt to be a comprehensive reference for location-specific recommendations. Some trusted travel medicine resources include:

• 1.
  

  World Health Organization (WHO) International Travel and Health ( http://www.who.int.easyaccess2.lib.cuhk.edu.hk/ith/en/ )

  
  
  
  
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    The WHO’s International Travel and Health website includes up-to-date information on outbreaks of concern to travelers and policies on travel-related vaccinations, disease distribution maps, vaccine and disease information, and travel health topics.

  
  
  
  
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  US Centers for Disease Control and Prevention (CDC) Health Information for International Travelers (The Yellow Book) ( https://wwwnc.cdc.gov/travel/page/yellowbook-home )

  
  
  
  
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    The Yellow Book has been a trusted resource for travel health since 1967 (Yellow Book, 2020). The full text is available free of charge online. It includes information on many travel health topics and guidelines for prevention and management of travel-related illnesses. The CDC website also includes destination-specific travel health recommendations and mobile apps related to travel health topics.

  
  
  
  
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  International Society for Infectious Disease ProMED Mail ( http://www.promedmail.org/ )

  
  
  
  
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    ProMED mail’s website lists infectious disease-related health alerts worldwide, and individuals can subscribe to receive email notifications free of charge.

  
  
  
  
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  Shoreland Travax ( www.travax.com )

  
  
  
  
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    Travax maintains up-to-date, country-specific travel health information that can be customized to provider and traveler reports that comprehensively list preventive measures that should be considered before travel. Use of Travax requires a fee-based subscription.

  
  
  
  
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  Global Infectious Disease and Epidemiology Online Network (GIDEON) ( https://www-gideononline-com.easyaccess2.lib.cuhk.edu.hk/ )

  
  
  
  
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    GIDEON web app and ebooks provide information on infectious disease threats by disease and by country. Use of GIDEON resources requires a fee-based subscription.

  
  

Health and Evacuation Insurance

An important consideration before leaving home is access to health care both at home and abroad. Those who may respond on short notice to disasters should have reliable access to medical care at home to receive routine preventive services, maintain optimal control of any medical conditions, and obtain timely pretravel care. Individuals who require routine medications or medical supplies must have adequate supplies available for short-notice travel. Before going overseas, all travelers should consider various scenarios requiring medical care for themselves, and in some cases for fellow travelers, and have plans in place for those contingencies. All travelers should have travel health insurance and are also advised to have means to pay at point-of-care for any required medical services. Some health insurance policies include coverage of care received abroad, but there may be caveats. It is important that travelers closely examine their health insurance policies before traveling, to determine if supplemental travel-specific health insurance may be necessary.

An additional consideration is the potential need for evacuation because of medical problems, or transport of remains in the event of death. Depending on the location, the local available level of care may not be adequate to manage complex medical situations and transport to a higher level of care may be necessary. Insurance that covers medical evacuation is recommended, as evacuation costs can be very high. Some travel health insurance policies include, or can be purchased concurrently with, medical evacuation insurance.

In additional to confirming travel health and medical evacuation insurance, one should become familiar with the names and locations of medical facilities in the travel destination. Health insurance providers may have specific recommended facilities. Embassies in the foreign country may maintain a list of recommended facilities. The traveler should be sure to have all necessary health insurance cards readily available during travel. Finally, all bills and receipts for medical care should be carefully retained.

Vaccinations

A key component of preparation for travel abroad is determining the need for vaccinations before travel. Characteristics of both the individual and the travel should be included in decision-making about pretravel vaccinations. One way to approach the multitude of vaccines that might be needed is to consider them within categories of routine, required, and recommended. Routine vaccinations include those that should be administered regardless of travel, such as childhood vaccines (e.g., polio, measles), age-, time-, or risk-based vaccines for adults (e.g., pneumococcal, tetanus boosters), and annual influenza vaccine. Required vaccines are those legally required for travel to certain locations, such as yellow fever. Recommended vaccines are those specifically indicated based on the travel location, environment or anticipated activities.

This chapter is not a comprehensive reference of all potential pretravel vaccines and does not include comprehensive details about administration, but rather provides an overview of vaccines that may be considered. This overview focuses primarily on pretravel vaccinations for adults, but some specific considerations relevant to children are included. Individual characteristics such as medical history, medications, immune status, age, and immunization history should be considered carefully within a pretravel medical encounter. Detailed, current information can be found at: https://wwwnc.cdc.gov/travel/page/yellowbook-home .

Vaccine Overview

Recommended

These vaccines may be recommended before travel, depending on location, duration, and types of activities:

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  Cholera: Cholera is a diarrheal (dysentery) illness caused by toxigenic Vibrio cholerae O-group 1 or O-group 139. These bacteria are found in fresh or brackish water, and may be associated with aquatic plants and life forms. Outbreaks of cholera are often associated with drinking water contaminated with the bacteria, frequently caused by contamination with the feces of infected individuals. Cholera outbreaks may occur in settings where sanitation and hygiene are inadequate and untreated water is consumed. Cholera is a concern in disasters and crises where the bacteria is endemic and water, hygiene, and sanitation (WaSH) systems are ineffective to prevent infection. Cholera illness is characterized by diarrhea (called “rice-water stools”), nausea, and vomiting. It can quickly cause significant dehydration if fluids are not replenished either via oral rehydration solution (ORS) or intravenous fluids.

  
  
  
  
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    Travelers to areas with endemic cholera who follow routine guidance to prevent travelers’ diarrhea (discussed later in this chapter), such as only drinking bottled water, are not at risk of cholera disease and typically do not require vaccination. Travelers who are responding to disasters and/or may work in healthcare settings with infected patients may have increased risk of cholera infection. Those with blood type O and low gastric acidity may be at risk of more severe disease if they become infected.

    
    
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    There are cholera vaccines available, but they are generally not part of routine vaccination recommendations. The WHO recommends vaccination only as a complementary measure after aggressive WaSH preventive efforts. Cholera vaccination may be used in the setting of a cholera outbreak, or as a preexposure prophylactic measure for individuals at higher risk. All currently available cholera vaccines are delivered orally. In the United States, the live attenuated CVD 103-HgR vaccine, marketed as Vaxchora, may be used in adults aged 18 to 64 traveling to areas with active cholera transmission. Specific areas that are considered to have active transmission can be found at https://wwwnc.cdc.gov/travel/diseases/cholera .

    
    
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    The Vaxchora vaccine is given as a single oral dose. It should be administered in a healthcare setting, with no eating or drinking 60 minutes before or after administration. It should be administered at least 10 days before potential exposure to cholera. Contraindications to the vaccine include history of allergy to a cholera vaccine or any severe, life-threatening allergy. The vaccine should not be given to those with a compromised immune system, or anyone who is pregnant or trying to become pregnant. The vaccine may be less effective in those who have recently (within last 14 days) received antibiotics or are currently taking chloroquine or plan to start it within 10 days. Vaccine may be shed in the stool for 7 days after administration. Care should be taken to avoid any contamination of immunocompromised close contacts. Adverse reactions are rare, but may include mild fatigue, headache, abdominal pain, nausea, vomiting, and diarrhea.

  
  
  
  
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  Japanese encephalitis: Japanese encephalitis (JE) virus is a single-stranded RNA virus, belonging to the genus Flavivirus , which is transmitted via the bite of an infected mosquito. Ixiaro is an inactivated Vero cell-culture-derived vaccine for those 2 months of age and older and is the only vaccine licensed in the United States. Vaccine recommendation should be guided by itinerary and length of stay in JE-endemic areas, time spent with unprotected evening or outdoor exposure, and the possibility (low) of serious adverse effects. The CDC’s Advisory Committee on Immunization Practices recommends JE vaccine for longer-term ( > 1 month) travelers or frequent travelers to JE-endemic areas, or for shorter-term (<1 month) travelers with an increased risk of JE (based on location, activity, lodging, season).

  
  
  
  
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    The primary vaccination dose and schedule varies by age. The two-dose series should be completed at least 1 week before travel. If ongoing exposure is expected, a booster dose should be given at least 1 year after the primary Ixiaro series is complete.

    
    
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    Pain and tenderness at the injection site are the most commonly reported side effects, with headache, myalgia, fatigue, influenza-like illness, and fever (in children) also possible. Serious adverse effects are rare. No studies have been conducted in pregnancy and generally administration of vaccine for pregnant women should be deferred, unless the risk of infection outweighs the risk.

  
  
  
  
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  Meningococcal: Neisseria meningitidis is a gram-negative diplococcus, spread through respiratory secretions by either asymptomatic carriers or those with meningococcal disease. Four meningococcal vaccines are available in the United States: Menveo, Manactra, Trumenba, and Bexero. A quadrivalent meningococcal conjugate vaccine (MenACWY) is recommended routinely for all between 11 and 18 years of age (first dose at age 11 or 12 years, followed by booster at age 16 years). Routine immunization is not recommended for other age groups except in those with persistent complement component deficiency or functional, anatomic asplenia, or HIV. Vaccination with serogroup B meningococcal (MenB) series may be recommended for those aged 16 to 23 years or those at increased risk (note: MenB vaccine is not routinely recommended for travel unless an outbreak of MenB is reported.)

  
  
  
  
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    Travelers to the “meningitis belt” of sub-Saharan Africa (from Senegal and Guinea to Ethiopia) during the dry season (December–June) and areas of recent outbreaks (information can be found at www.cdc.gov/travel ) should be vaccinated with meningococcal vaccine. Travelers to the Kingdom of Saudi Arabia (KSA) for Umrah or the Hajj or for seasonal work are requested to document meningococcal vaccination within the last 3 years (polysaccharide vaccine) or 5 years (conjugate vaccine), but no more recently than 10 days before arrival. Visa requirements should be checked with the KSA embassy.

    
    
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    Infants less than 9 months should be vaccinated with MenACWY-CRM (Menveo). At 2 months of age, MenACWY-CRM should be administered as a four-dose series (2, 4, 6, and 12 months). If initiating vaccination at 7 to 23 months of age, MenACWY-CRM should be administered as a two-dose series (second dose administered at ≥12 months of age and ≥3 months after the first dose). If needed for travel itinerary, the second dose can be administered as early as 8 weeks following the first.

    
    
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    MenACWY-CRM or MenACWY-D (Menactra) may be used in travelers from 9 months of age through age 55 years. For travelers 9 to 23 months of age, two doses of MenACWY-D should be administered at least 3 months between doses, unless needed for travel (can administer 8 weeks apart to precede travel). A single dose of a MenACWY vaccine (MenACWY-CRM or MenACWY-D) is recommended for most travelers 2 years of age and over.

    
    
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    International travelers previously vaccinated with a quadrivalent vaccine should receive a booster (children: after 2 years and every 5 years; those > 7 years: after 5 years and every 5 years).

    
    
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    Injection site pain, swelling, and low-grade fevers may be side effects after MenACWY vaccination, but severe adverse reactions are rare.

  
  
  
  
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  Rabies: Rabies is caused by neurotropic viruses in the family Rhabdoviridae, genus Lyssavirus, and the most common mode of transmission is inoculation of saliva secondary to an animal bite. Preexposure vaccination is recommended based on occupation of traveler (hunters, forest rangers, taxidermists, laboratory workers, stock breeders, abattoir workers, veterinarians, and spelunkers), occurrence of animal rabies in the destination country, activity of the traveler, duration of stay, and availability of treatments. Persons planning to stay over 30 days in a rabies-endemic area, such as most countries in Latin America, Africa, and Asia (except Taiwan and Japan) should be vaccinated.

  
  
  
  
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    Preexposure vaccination includes three pretravel intramuscular injections given on days 0, 7, and 21 or 28 in the deltoid with human diploid cell rabies vaccine (HDCV) or purified chick embryo cell (PCEC) vaccine. If three doses of rabies vaccine cannot be completed before travel, the traveler should not start the series.

    
    
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    Travelers who have completed a three-dose preexposure rabies immunization series or have received full postexposure prophylaxis (PEP) are considered previously vaccinated and do not require routine boosters. Routine testing for rabies virus-neutralizing antibody is not recommended for international travelers who are not otherwise in the frequent or continuous risk categories.

    
    
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    PEP is recommended for all persons exposed to rabies virus, irrespective of immunization history. See Rabies in Chapter 3 for details about PEP.

    
    
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    Local reactions such as pain, erythema, swelling, or itching, or mild systemic reactions such as headache, nausea, abdominal pain, muscle aches, and dizziness, may occur. Booster vaccinations with HDCV may result in systemic hypersensitivity reactions (urticaria, pruritus, and malaise). Once initiated, rabies PEP should not be interrupted or discontinued because of local or mild systemic reactions to rabies vaccine. If an adverse event occurs with one of the vaccine types, consider switching to the alternative vaccine for the remainder of the series. PEP is not contraindicated in pregnant women.

    
    
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    Chloroquine phosphate or mefloquine may weaken the antibody response to HDCV when HDCV is given intradermally—if giving the vaccination any time near the taking of these medications, consider IM route; corticosteroids, chemotherapy, antimalarials (chloroquine, mefloquine), and immunosuppressive agent usage may warrant testing for antibody response.

    
    
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    Other: preexposure immunization does not eliminate the need for the treatment with more vaccine after an exposure to rabies; any person exposed to rabies should always contact local or state health authorities and a personal physician for guidance – if the state epidemiologist is unavailable, call the CDC during Eastern working hours at (404) 639-1050 or (404) 639-2888 at any other time; for travelers abroad, if the availability of safe, effective postexposure products are in question, one should contact the nearest US embassy or consulate.

  
  
  
  
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  Typhoid: Typhoid and paratyphoid fever are potentially life-threatening illnesses caused by Salmonella enterica serotypes typhi and paratyphi A, B, and C. Transmission is by consumption of water or food contaminated by feces of an ill person or an asymptomatic carrier.

  
  
  
  
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    Typhoid vaccine is recommended for travelers to areas at high risk for typhi exposure. The two vaccines available in the United States are Vi capsular polysaccharide vaccine (ViCPS) (Typhin Vi) or oral live attenuated vaccine (Vivotif). One 0.5-mL IM dose of ViCPS should be administered at least 2 weeks before travel to those 2 years of age or older, with a booster every 2 years for those who continue to be at risk. Oral Ty21a vaccine administration for those 6 years of age or older is one capsule every other day for 4 days (taken with cool liquid no warmer than 98.6°F), taken at least 2 hours after a meal and 1 hour before a meal. A booster is recommended every 5 years for those who remain at risk.

    
    
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    ViCPS vaccine may cause headache and injection site reactions. Reactions reported following Ty21a include abdominal discomfort, nausea, headache, fever, diarrhea, vomiting, and rash. Vaccination with Ty21a should be delayed for 72 hours following antibiotic treatment and antibiotics should not be administered within 72 hours of last dose of Ty21a vaccine. For pregnant women at high risk for typhoid exposure, ViCPS administration may be considered.

  
  

Prevention and Chemoprophylaxis of Vector-Borne Disease

The next important travel health consideration is whether the travel destination increases risk of vector-borne diseases, and what forms of prevention and prophylaxis are recommended. Vectors such as mosquitoes and other insects can transmit diseases caused by bacteria, viruses, and parasites. The first line of defense against vector-borne diseases is to avoid bites from vectors using mechanical, chemical, behavioral, and environmental measures. Mechanical barriers include use of netting (ideally impregnated with insecticide) while sleeping, wearing long sleeves and long pants, and tucking pants into shoes or boots. Chemical barriers include use of insect repellents, such as DEET, picaridin, and permethrin. DEET and picaridin can be applied directly to the skin in sprays, liquids, lotions, and on wipes. Products should be at least 30% active ingredient. Repellents should be reapplied regularly, according to recommendations for the particular product used. When concurrently applied with sunscreen, sunscreen should be applied first followed by insect repellent. Clothing can be pretreated with permethrin, which will last through many washes, and some travel clothing can be purchased already treated. Military uniforms are often pretreated with permethrin. Treatment needs to be completed 24 to 28 hours before travel to ensure drying of the permethrin solution. Behavioral measures such as avoiding being outside at times of highest risk for bites may be implemented; however in a disaster response scenario one may have little control over when time is spent outdoors. Skin checks for ticks should be performed after time spent in an area at risk for ticks. Environmental measures such as spraying of insecticides can be very helpful to control vector populations, but also may not be available in a disaster response setting.

Malaria is the vector-borne disease typically of greatest concern for travelers. Malaria is caused by several species of Plasmodium parasites and is transmitted from person to person by mosquitoes of the Anopheles genus. The WHO estimated there were 214 million malaria cases and 438,000 malaria deaths worldwide in 2015. Transmission occurs in much of Africa, parts of Latin America and the Caribbean, parts of Asia, and some South Pacific islands. The distribution of Plasmodium species varies by geographic location.

Malaria causes a febrile illness that can be debilitating and sometime fatal if untreated. Most clinical cases are caused by P. falciparum or P. vivax ; P. falciparum malaria causes severe disease and can be fatal, while P. vivax is often less severe. Additional species that can cause clinical malaria are P. ovale , P. malariae , and P. knowlesi . Prompt diagnosis and treatment with appropriate medication(s) are critical. Development of drug resistance has been a continual problem for treatment of malaria, with limited treatment choices remaining in some geographic areas. Details of clinical malaria infection, diagnosis and treatment will be covered in detail in Chapter 3 .

Risk of malaria transmission can vary greatly depending on destination (including geographic variation within a country), season of travel, and anticipated activities. Recommendations for prevention of malaria should be tailored to the individual traveler. However, for travelers responding to a disaster or other contingency, a conservative approach to prevention may be advised since location and activities may change unexpectedly.

The best way to avoid infection with malaria is to avoid mosquito bites via the preventive measures covered above. The Anopheles mosquitoes tend to be nocturnal feeders, biting primarily between dusk and dawn. Sleeping under bed nets, avoiding outdoor activities at night, proper wear of clothing, and use of repellents should be practiced rigorously. Equally important is use of malaria chemoprophylaxis when appropriate. There are multiple regimens available, which should be selected based on information about the endemic species in the travel destination, local drug resistance patterns, and the medical history and preferences of the traveler. Current travel health resources should be consulted before travel, as recommendations may change over time. Here is a summary of commonly used chemoprophylaxis regimens:

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  Atovaquone-Proguanil (US trade name Malarone): This combination provides effective prophylaxis for all malaria parasite species. It is dosed 250 mg/100 mg (single tablet) once daily in adults, and should be started 1 to 2 days before entry into an area at risk for malaria. It should be continued for 7 days after departing the malaria risk area; however, some studies suggest effectiveness if continued just 1 day after departing the area. The half-life is longer than other daily prophylactic medications such as doxycycline, so a missed dose will not likely decrease prophylactic effectiveness. Atovaquone-proguanil is generally well tolerated without significant side effects when taken with food or a milky drink. This is a good choice for short-term travel, given the minimal dosing required pre- and posttravel. Atovaquone-proguanil cannot be used in pregnant or lactating women, children weighing less than 5 kilograms, or those with severe renal impairment. This is the newest option for malaria chemoprophylaxis and is usually of higher cost than other options.

  
  
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  Chloroquine (US trade name Aralen) or hydroxychloroquine (US trade name Plaquenil): Although it is a historically important malaria treatment, development of resistance has limited chloroquine’s use for treatment and prophylaxis in much of the world. However, some areas of Mexico, Central America, and the Caribbean have malaria parasites that remain susceptible. Chloroquine is dosed 500 mg salt (300 mg base) once weekly in adults, starting 1 to 2 weeks before travel, and continuing until 4 weeks after departing the area at risk for malaria. Potential side effects include gastrointestinal upset, and long-term use can cause retinopathy. It can potentially exacerbate psoriasis. There are few contraindications to chloroquine; it can be used in pregnant and lactating women and children. Hydroxychloroquine is a similar prophylactic option, and may be better tolerated in some individuals. It is dosed 400 mg (310 mg base) once weekly in adults, starting 1 to 2 weeks before travel and continuing until 4 weeks after departing the area at risk.

  
  
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  Doxycycline: The antibiotic doxycycline may be used to prevent malaria, and can be used in all geographic areas. It is dosed 100 mg once daily in adults, starting 1 to 2 days before entering the area at risk of malaria, and continued for 4 weeks after departing. Given its relatively short half-life, consistent daily dosing is critical. Some may experience side effects, including gastrointestinal problems such as dyspepsia, nausea/vomiting, esophageal ulcers, and inflammation. Doxycycline is also associated with increased photosensitivity and vaginal yeast infections. For individuals taking medications that may have risk of phototoxicity, doxycycline should be avoided. Doxycycline cannot be used in pregnant and lactating women or children under 8 years of age. An additional benefit of doxycycline use is that it also may prevent leptospirosis and rickettsial diseases.

  
  
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  Mefloquine (US trade name Lariam): Mefloquine was developed in response to growing chloroquine resistance. It is dosed 250 mg salt (228 mg base) once weekly in adults, starting 1 to 2 weeks before travel, and continuing until 4 weeks after departing the area at risk for malaria. Resistance to mefloquine is present in some areas of Southeast Asia, and monitoring is ongoing for spread of resistance to other geographic areas. Mefloquine is associated with neuropsychiatric side effects such as vivid dreams or nightmares, anxiety, depression, confusion, restlessness, and dizziness. There are also risks of cardiovascular conduction depression. Mefloquine should not be used in individuals with preexisting psychiatric disorders, seizure disorders, or cardiovascular disorders. Mefloquine can be used in pregnant and lactating females and in children. The potential psychiatric side effects of mefloquine have received a great deal of media attention in the last decade, prompting a US Food and Drug Administration boxed warning, and it is no longer considered as a first line malaria prophylactic medication in the US military.

  
  
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  Primaquine: Primaquine is an option for primary malaria chemoprophylaxis in areas with more than 90% Plasmodium vivax malaria, and is used for presumptive antirelapse therapy, occasionally referred to as terminal prophylaxis, after departing areas with high levels of Plasmodium vivax and ovale . Primaquine treats hypnozoites in the liver, in contrast to all other chemoprophylactic agents that treat blood stages of the malaria parasite. For primary prophylaxis, primaquine is dosed 52.6 mg salt (30 mg base) daily in adults, starting 1 to 2 days before travel, and is continued for 7 days after departing the area at risk for malaria. For presumptive antirelapse therapy, the dosing is 15 to 30 mg base daily for 14 days after departing the area at risk. Presumptive antirelapse therapy is usually recommended in longer-term travelers. Primaquine can cause hemolysis in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency, so it should not be prescribed in those not screened for G6PD deficiency. It is contraindicated in pregnancy, but can be used in lactating women if the infant has been screened and does not have a G6PD deficiency. It can be used in children without G6PD deficiency. Primaquine may cause gastrointestinal side effects, which can be lessened by taking it with food.

Additional vector-borne diseases of concern are arboviruses, or viruses spread by arthropod vectors, such as YF, dengue, Zika, chikungunya, West Nile, JE, and others. These viruses can cause a range of clinical syndromes from mild rash to hemorrhagic fever to encephalitis. The geographic distributions of these viruses and their vectors vary and are dynamic, especially given the impacts of climate change, land-use changes, and global transit and travel. For travelers, preventive measures to avoid insect bites are key to preventing these infections. Some of the mosquito vectors of these viruses breed rapidly in standing water, such as species of the Aedes genus. Avoiding the accumulation of water in tires, pots, containers, and other areas can help decrease the vector burden. There are vaccines widely available for YF and JE, and vaccines in development for dengue, Zika, and other viruses. A 2015 outbreak of Zika in Brazil brought worldwide attention to the virus as it spread elsewhere in the western hemisphere. Zika infection during pregnancy has been linked with microcephaly and other brain abnormalities in fetuses. Zika infections have also been associated with Guillain-Barre syndrome. Zika-related travel guidance includes a recommendation that pregnant women not travel to areas with active Zika transmission, and that couples use barrier contraception for 6 months after males have been in an area with active Zika transmission because the virus can remain in the semen for several months.

Ticks, fleas, lice, and mites are vectors for bacterial, viral, and parasitic pathogens. Ticks are usually found in wooded or grassy areas. Fleas, lice, and mites are often associated with animals and may be found in urban or rural environments. Rickettsial bacterial infections are spread by these vectors in most of the world. Tickborne encephalitis (TBE) is a viral infection spread by ticks in Europe and Asia. Vaccines for TBE are produced in Austria, Germany, and Russia. Travelers to endemic areas should consider receiving the vaccination if available in their home country, or when they arrive in the area at risk. Ticks can also spread the parasitic disease babesiosis. Prevention of diseases caused by ticks, fleas, lice, and mites includes typical insect bite prevention measures, as well as controlling rodent and other animal populations in areas of human habitation. Maintaining good hygiene and performing skin checks for ticks are also important preventive measures.

Flies and sandflies also serve as vectors for infectious pathogens. Flies can directly transmit bacteria or viruses, acting as fomites. Blackflies can transmit onchocerciasis, or river blindness. Sandflies can transmit leishmaniasis. Contact with flies and sandflies should be avoided with preventive measures discussed above. Sandflies are quite small (2–3 mm) and may be able to pass through an ordinary bed net, but insecticide treatment of bed nets will help improve effectiveness against these small insects.

Finally, animals also serve as vectors of disease. Bites and scratches can result in skin infections, or can transmit rabies virus. Bites of certain poisonous snakes or spiders can result in illness or death. Travelers should avoid close contact with animals to prevent bites. The pretravel medical encounter is the appropriate time to determine if tetanus vaccination is up to date and discuss the option of rabies preexposure prophylaxis. Typically, rabies preexposure prophylaxis is recommended for those traveling longer than 1 month to areas potentially at risk for rabies, especially rural areas in developing countries. Whether an individual has had preexposure prophylaxis or not, it is important to seek medical care after an animal bite for PEP with rabies immune globulin and/or rabies vaccine. Details of this management will be discussed further in Chapter 3 . Those with snake or spider bites should also seek medical care, as antivenom may be available in some healthcare facilities. As part of preparation for travel, individuals may wish to investigate where there are local medical facilities with therapies that could be needed acutely for animal bite situations.

Travelers’ Diarrhea

The most common affliction of travelers is gastrointestinal illness with diarrhea and other bothersome gastrointestinal symptoms, such as nausea, vomiting, cramps, abdominal pain, and bloating. Known as travelers’ diarrhea (TD) in the setting of foreign travel, this may affect up to 10% to 40% of travelers, depending on itinerary and characteristics of the traveler (Steffen, 2015). Travel destination and travel style, including where food purchases are made and where consumed food is prepared, likely influence risk the most. Although the ultimate goal is prevention, this is often challenging for travelers, especially those traveling to low-income regions. Therefore, travelers need to be prepared to manage and treat TD if it occurs.

TD is often caused by ingestion of fecally contaminated food or water, and the etiologic agent is most often bacterial. TD is present if an individual has three or more unformed stools in a 24-hour period plus one or more additional symptoms, such as cramping, tenesmus, nausea, vomiting, fever, or fecal urgency (Steffen, 2015). Severity is variable, ranging from discomfort that does not impact activities to debilitating pain and other symptoms. Although most cases are self-limited and can be managed effectively, in some cases TD can result in life-threatening dehydration and even death.

The most common causes of TD that occur in developing regions include the following: ETEC (heat-labile and heat-stable toxin producing Escherichia coli), E. coli (enteroaggregative and diffusely adherent), noroviruses, rotavirus, Salmonella species , Campylobacter jejuni, Shigella species , Aeromonas, Plesiomonas shigelloides, Bacteroides fragilis , and Vibrio species; there are regions where parasites such as Giardia duodenalis, Cryptosporidium species, Entamoeba histolytica, and Microsporidium species are also potential culprits (Steffen, 2015). The average duration of untreated TD is 4 to 5 days and, although between 12% and 46% of patients may have short-term “disability,” most report only 1 day of incapacitation (Steffen, 2015). TD is also sometimes linked with long-term sequelae such as irritable bowel syndrome (IBS) (Riddle, 2016; Steffen, 2015).

Travelers can learn the approximate risk of developing TD at their destination by examining historical data. Prevention of TD is primarily focused on avoiding consumption of contaminated liquids and foods, but this can be more challenging than the common advice “boil it, cook it, peel it, or forget it” implies. In some locations there is inadequate processing (including filtration, treatment, and testing) of municipal water at baseline. In a disaster scenario, even locations with adequate water processing infrastructure at baseline may have increased risk for contamination. It is best to avoid consuming local municipal water if the reliability of water processing infrastructure is unclear. Bottled water from a trusted processing company is typically safe for consumption. Water purification with a reverse osmosis water purification unit (ROWPU) may be employed in a disaster setting, producing large volumes of safe-for-consumption water in a short amount of time. Individual water filtration devices may also be used; these may be in the form of a pumping-type device or a small water bottle that filters directly. Water may also be boiled (to rolling boil for at least 1 minute) or treated, to be safe for consumption.

Travelers may consider bringing along items to assist in purification of water, especially in areas with a higher risk of TD. Iodine tablets are a quick and easy way to purify water and can be easily transported. Low-concentration bleach products can also be used to treat water, although it is important to understand the products that should be used in such scenarios. The CDC and a social marketing nongovernment organization Population Services International worked together to produce and market the Safe Water System chlorination product (Lantagne, 2009). Before travel, a small personal filtration device may be a good investment.

Besides water, other liquids may become contaminated in processing or preparation. It is best to drink bottled products only when you have seen them opened and can confirm that there was a tight seal. Fruit juices that are prepared fresh may be at risk of contamination. Generally, hot beverages like coffee or tea are low risk; however, if they are made with contaminated water and not heated sufficiently, they may also carry risk. Finally, consumption of ice should be avoided as often ice is made using municipal water which may be contaminated.

Appropriate food selection can be even more challenging when attempting to prevent TD. Because many eating establishments may have sanitation and cooking practices that are inadequate and not readily apparent to travelers, even the most careful traveler may consume the pathogens that cause TD. Foods are often not brought to the correct temperature, may be left out at room temperature, or may be subject to insects when not covered appropriately (Steffen, 2015). Whereas travelers should exert caution in choosing eating establishments and the foods they eat, additional measure might be considered to protect from TD more fully.

In addition to liquid and food preventive measures, there is a high level of evidence that prophylactic use of bismuth subsalicylates have moderate effectiveness in preventing TD and may be considered in travelers who do not have contraindications to use and can adhere to the dosing requirement (Riddle, 2016). The recommended dose is two tablets, four times a day (mealtimes and at bedtime) for up to 3 weeks and individuals should be warned that their stools and tongues will turn black. It should not be taken as prophylaxis when other salicylates are being used or when a trip is longer than two weeks and should not be used by individuals with inflammatory bowel disease or HIV (Riddle, 2016).

Antibiotic chemoprophylaxis can also be considered to prevent TD, especially in high risk groups. Historically, concerns about antibiotic resistance and side effects and questions about effectiveness have precluded guidelines recommending the routine use of prophylactic antibiotics. However, the increasing recognition of postinfectious IBS as a public health issue and the availability of rifaximin, a nonabsorbable antibiotic with an improved safety profile, have led to more recent recommendations to consider rifaximin in certain populations (Riddle, 2016). A traveler who is at high risk for TD or for whom TD could pose serious medical consequence or a significant negative impact on the mission of the travel, might consider rifaximin.

Environmental Factors

Travel may involve rapid changes of environmental conditions, which can have health impacts. Travelers should be prepared for potential temperature extremes. Environmental heat exposure may increase risk for heat illness. Classic heat illness occurs primarily in young children or the elderly, and exertional heat illness occurs more often in young adults. Heat illness occurs when the physiologic responses to heat stress are inadequate and core body temperature rises, resulting in a spectrum of symptoms ranging from cramps to syncope to organ failure. Heat stroke, which includes mental status changes, is a medical emergency and will require contact with the local healthcare system.

Lack of adequate acclimatization is a risk factor for heat illness. Disaster responders may quickly become involved in strenuous duties upon arrival to a new location and put themselves at risk for heat illness. When traveling to a significantly warmer environment, individuals should limit strenuous physical activity in the initial days. Some acclimatization protocols recommend up to 2 weeks of gradual increase in activity. Additional risk factors include prior heat illness, obesity, poor physical fitness, sleep deprivation, illness, excessive alcohol use, dehydration, and certain medical conditions and medications. The medications that may increase risk of heat illness include anticholinergics, antihistamines, antiepileptics, tricyclic antidepressants, amphetamines, lithium, beta-blockers, and diuretics. Avoiding alcohol use, hydrating well, and getting adequate sleep can help avoid heat illness. There is no specific threshold of environmental heat that portends a greater risk of heat illness; each individual’s physiology is unique and heat illness can occur at temperatures that might not be considered very extreme. It is important to be cognizant of potential heat-related symptoms, and act quickly to cool body temperature if there is any concern for heat illness.

Cold environments can also result in health problems, although this is uncommon with proper planning and gear. Most travel-related cold injuries are related to accidents or unexpected severe weather. Hypothermia can occur rapidly if an individual becomes wet or exposed in cool conditions. Those who will be traveling on or working around cold bodies of water should make sure to have personal flotation devices available, as immersion hypothermia can render a person unable to swim or tread water in less than 15 minutes. Other cold-related conditions include nonfreezing injuries such as trench foot, pernio (chilblains) and cold urticaria, and the freezing injuries of frostbite. Frostbite can result in loss of digits if not recognized and treated promptly. Severe hypothermia and frostbite will likely require contact with the local healthcare system and may necessitate medical evacuation depending on the treatment capabilities available locally.

Depending on the travel destination, the level of exposure to ultraviolet (UV) light may increase significantly. Higher elevation, tropical latitude, and increased reflection from snow or sand increase risk for sunburn and associated health risks. Also, some medications may increase sun sensitivity, including medications that may be only taken during travel (e.g., doxycycline for malaria chemoprophylaxis). Prevention of sunburn requires diligent preventive efforts. As much as possible, clothing should provide the first defense against UV rays. Some clothing items provide a specified level of sun protection factor (SPF). A wide-brimmed hat can help decrease exposure of the face and neck. Sunscreen with a SPF of at least 15 should be used routinely on any exposed skin and reapplied regularly, approximately every 2 hours. A waterproof or water-resistant sunscreen will provide longer duration of protection. Sunscreen should be applied before insect repellents and combination products should be avoided since sunscreen will need to be reapplied more frequently than the repellent. Severe sunburns are like thermal burns and may require medical care.

Rapid ascent to high altitude environments can result in acute mountain sickness (AMS), high altitude cerebral edema (HACE), and high altitude pulmonary edema (HAPE) in those not acclimatized. These conditions can be rapidly fatal if not promptly recognized and descent quickly initiated. There is no specific altitude at which all unacclimatized persons will have difficulty, as each individual’s physiology and susceptibility differ, although rapid ascent from low altitude to above 9000 ft (2750 m) sleeping altitude should trigger consideration of preventive measures. Pretravel exposure to 9000 ft (2750 m) for 2 nights or more within 30 days of travel can be very helpful in preventing altitude illnesses. Gradual ascent to higher elevations, if possible, decreases risk of altitude illnesses. Spending a few days at 8000 to 9000 ft (2500‒2750 m), and then moving sleep altitude no greater than an additional 1600 ft (500 m) per day is advised. If a gradual ascent is not possible, use of prophylactic medications may be considered. Acetazolamide (US trade name Diamox) is most commonly used for AMS/HACE prevention, at 125 mg twice a day (250 mg if weight >100 kg) starting 1 day before ascent and continuing the first 2 days at high altitude. Acetazolamide is contraindicated in individuals with a history of an anaphylactic reaction to a sulfa drug, although in those with nonanaphylactic reaction to sulfa the risk of a reaction to acetazolamide is quite low. Acetazolamide causes increased urination and paresthesias of the fingers and toes. Additional medications that are used for treatment of altitude illnesses (dexamethasone, nifedipine) can be considered for prophylactic use in those at high risk and not eligible for acetazolamide. This topic will be discussed further in Chapter 9 .

Another environmental consideration is potential exposure to bodies of water. As mentioned above, submersion in cool or cold water can quickly result in hypothermia. Accidents of vessels of conveyance can result in drowning; travelers should be mindful of whether personal flotation devices are available on ferries, boats, or ships. When near the ocean, travelers should be aware of tides and surf because conditions can change quickly. Sand at the beach can be home to helminths; wearing footwear on the beach helps prevent infection. Freshwater exposure may increase risk of leptospirosis or schistosomiasis, depending on location. For those with anticipated freshwater exposure in an area known to be at risk for leptospirosis, doxycycline 200 mg once weekly starting 1 or 2 days before exposure and continued through the period of exposure, may be used as chemoprophylaxis. Flooding situations can increase risk for trauma and contact with water that is potentially contaminated with pathogens and chemicals.

Air pollution is increasingly a health threat for travelers. In some large cities, the particulate matter in the air frequently reaches unhealthy levels. Those with preexisting respiratory or cardiovascular conditions, such as asthma, chronic obstructive pulmonary disease, and heart disease, may wish to monitor air quality measures before travel. The WHO provides historical information on air pollution by country (gamapserver.who.int/gho/interactive_charts/phe/oap_exposure/atlas.html) and some US embassies provide real-time air quality information on their websites. Those at risk should avoid strenuous exercise when air pollution levels are elevated. Additionally, travelers may be at risk of indoor air pollution from cigarette smoking and cooking fuels (e.g., charcoal, wood, kerosene). Carbon monoxide poisoning can occur because of unvented cooking stoves and space heaters, or improper placement of generators.

Finally, a travel-related change in environment may increase risk for accidents and injuries. An unfamiliar environment, different safety standards, hazardous traffic, and limitations of communication can all contribute to this increased risk. Injuries are the leading cause of preventable death in travelers. Travelers should use common sense approaches to decrease injury risk, such as using seat belts in vehicles (or choosing not to ride in vehicles that do not have seat belts), avoiding driving at night or peak traffic hours, exercising caution when crossing roads, and not using cellular telephones when driving (or allowing drivers to use them while driving). The Association for Safe International Road Travel ( www.asirt.org ) provides specific information about road safety for some countries (requires no-fee registration to access). It is important to maintain situational awareness while traveling. Travelers should not consume excessive alcohol or any other substances that may impair alertness or decision-making ability.

Other Infectious Risks

Sexually transmitted infections (STIs) are common worldwide. Travelers who engage in casual sex while in foreign countries increase their risk of acquiring STIs, including HIV. Prevalence of certain infections vary by country, so a traveler may be exposed to infections not common in his or her home country. Commercial sex workers often have high rates of certain STIs. Prevention includes abstinence from sex with new partners during travel, or use of male latex condoms. Consistent use of condoms can prevent transmission of some, but not all, STI pathogens. Pretravel vaccination for hepatitis A and B is also preventive because both viruses can be spread sexually. Posttravel testing for STIs including HIV may be indicated for those at increased risk. Certain travelers at high risk for HIV exposure may consider preexposure prophylactic treatment.

Travelers may be at risk for exposure to blood and bodily fluid-borne pathogens, especially travelers involved in patient care during responses to disasters or other contingencies. Healthcare workers should practice standard precautions and enhanced infection control precautions as indicated. Pretravel training on use of personal protective equipment can help prepare healthcare personnel to protect themselves. Healthcare workers’ immunization records should be carefully scrutinized to ensure protection from vaccine-preventable infections that may be encountered in the healthcare setting. These include measles, mumps and rubella, hepatitis B, varicella (immunization or prior infection), tetanus, diphtheria, and pertussis, and annual influenza. Contact with blood or bodily fluids by percutaneous exposures, such as needle sticks, puts healthcare workers at risk of infection with hepatitis B, hepatitis C, and HIV. Depending on the assessed risk of infection, the healthcare worker may opt to initiate PEP treatment for HIV. The regimen used most commonly in the United States is a three-drug regimen daily for 4 weeks; either tenofovir-emtricitabine (300/200 mg once daily) plus dolutegravir (50 mg once daily) or tenofovir-emtricitabine (300/200 mg once daily) plus raltegravir (400 mg twice daily). Laboratory testing for HIV should occur at baseline, 6 weeks, 3 months, and 6 months. Laboratory testing for hepatitis C should occur at baseline and three or more weeks after potential exposure. If susceptible to hepatitis B, there is also a regimen for PEP.

Another travel-related infectious risk that is heightened for healthcare workers is TB. This bacterial infection is most commonly spread through respiratory aerosols from individuals with active pulmonary TB. Healthcare workers should use respiratory protection, such as N-95 respirators, when working with patients known or suspected to have TB. Healthcare workers may be screened periodically with tuberculin skin test (TST) or interferon-gamma release assay (IGRA) for evidence of latent TB infection. Healthcare workers who may have increased risk of exposure to TB during travel should have pretravel screening with TST or IGRA before travel and again 8 to 10 weeks after return. TB will be covered further in Chapter 3 .