Although pathologists and medical technologists generally work in the hospital setting, they may be involved in either hospital care or posthospital care. For example, pathologists and medical technologists who are involved in surgical pathology, cytology, and clinical laboratories are usually involved in hospital care, whereas pathologists and morgue personnel involved in autopsies could be considered posthospital healthcare workers. Moreover, some pathologists and medical technologists work in reference
laboratories that are not associated with a hospital. As nonhospital-associated freestanding operations, these reference laboratories most often do not have the assistance of hospital infection preventionists (IPs) and, hence, may fall short in providing protective measures appropriate to the infectious risks. The use of such freestanding reference laboratories for testing of specimens from hospitalized patients and for testing of specimens from patients in the prehospital and posthospital setting is increasing. This, in turn, has resulted in potential infectious risks for personnel involved in the packaging, handling, and transport of medical specimens. Accordingly, the PHS and CLSI have developed regulations and guidelines for proper procedures for the handling and transport of diagnostic specimens and etiologic agents (13,26). Moreover, the CLSI, the CDC, and the National Institutes of Health (NIH) address biosafety issues in microbiology and biomedical laboratories (19,27). All pathologists and medical technologists have unique risks for occupationally acquired infections because of contact with patient specimens. The risk for pathologists and medical technologists involved in clinical laboratories is covered in Chapter 77. The risks for pathologists who perform autopsies (19,28,29) are addressed in this chapter. Biosafety considerations for autopsies are important topics that often are not addressed by hospital infection control committees.

Cost containment has shifted a great deal of medical care from the hospital setting to the outpatient setting. Accordingly, infection control issues in the home care and hospice setting are now being addressed (30). Although the home setting is considered to have fewer infection risks, studies have not confirmed this (31). Clearly, some patients receiving home healthcare have infections and, thus, pose a risk for home healthcare workers (30,31). Home healthcare patients are often elderly and may have unrecognized tuberculosis (32). AIDS patients are another group of patients commonly cared for in a domiciliary setting (33). Such infection risks in the home healthcare setting are only beginning to be studied. Research is needed to delineate such risks and to identify ways to minimize or prevent these infections from being transmitted to home healthcare workers. The topic of infection control in the home healthcare setting is discussed in Chapter 99.

The number of persons entering assisted-living facilities and nursing homes for residential long-term care is substantial and is increasing. Many of these nursing home, residential care, and assisted-living patients enter such facilities directly from the hospital. The need for residential long-term care facilities to provide comprehensive infection control programs is well recognized (34,35 and 35a). A number of infectious diseases problems are common to long-term care facilities and often are unappreciated (36 and 36a). A typical presentation of infections is generally acknowledged and may lead to delays in diagnosis and treatment of infections such as tuberculosis. The physical plant of many long-term care facilities is often a factor; many residents live in confined settings with few private rooms, and rooms appropriate for isolation often are not available. Finally, many long-term care facilities experience rapid turnover of personnel, and residential long-term care workers frequently have less training than those in the hospital setting. Longterm care facilities need a well-developed infection control program that in part identifies and minimizes the risk of occupationally acquired infections. Such programs can be developed best with the assistance of the hospital-based IP (37 and 37a) (see Chapter 98).

The delivery of healthcare continues to shift from the hospital setting to the outpatient setting (23). For example, an increasing number of surgical procedures are done on an outpatient basis, and postoperative complications are now seen by emergency departments (35 and 35a). Thus, many outpatient healthcare workers can be considered posthospital workers and share the risks of posthospital healthcare workers (36 and 36a). The Joint Commission (TJC) is actively reviewing infection control programs for outpatient services that are affiliated with hospitals and has published standards for ambulatory surgery centers (37 and 37a).

Another shift in providing healthcare has been the establishment of rehabilitation facilities. Follow-up care of many illnesses is now carried out in these facilities, and healthcareassociated infections are common (38). Healthcare workers in these facilities have similar risks to hospital workers, yet these rehabilitation facilities may not be associated with a hospital and have access to IPs and policies. Surveillance and infection control measures, nonetheless, are needed (35 and 35a).

Freestanding dialysis facilities have become very common. Clearly, the risk for many blood-borne pathogens in such facilities is high (39). These centers may not have access to IPs and policies; however, surveillance and infection control measures clearly are needed. Accordingly, the CDC has published guidelines and recommendations for the prevention and control of dialysis-associated infection (40).

Freestanding healthcare laundries serving multiple hospitals have been established in many cities. The risk for these workers is high for certain infections, including blood-borne pathogens because of the presence of sharp objects such as needles (41). Workers in these laundries also are at risk for scabies. Laundries may not have access to IPs and policies. Guidelines and recommendations for the prevention and control of infections in the laundry setting are included in the CDC guidelines for infection control in healthcare settings (42).

The risk for exposure to infectious agents during autopsies is becoming better known and has resulted in guidelines for performing autopsies to minimize this risk (17,28,29,43). In particular, guidelines designed to minimize the risk of human immunodeficiency virus (HIV) infection (44,45) and tuberculosis (46) have been published. Funeral home workers can be considered posthospital healthcare workers and share some of the same risks as a pathologist performing an autopsy (47). A study of funeral practitioners has noted a low rate of occupational exposures and a high rate of hepatitis B vaccination in comparison with prior studies, which suggests both improved education for and compliance with the recommendations for preventing transmission of blood-borne pathogens in the workplace (48). Such efforts should be continued.

The potential for exposure to infectious diseases in trash haulers and landfill operators is a very important issue (49,50). Although minimal (51,52), the risk is real and should be controlled. The proper disposal of medical waste is a key factor in controlling this risk; CLSI Document GP5-A “Clinical Laboratory Waste Management: Approved Guideline—Second Edition” addresses this topic (53), and federal law now requires compliance (54).

The transmission of Mycobacterium tuberculosis occurs mainly by inhalation of droplet nuclei (55). The influenza A virus may be spread by droplet nuclei (7). Finally, there is also evidence that in some cases the coronavirus responsible for SARS has been spread by droplet nuclei (8). These droplets are airborne particles and must be <5 µm in size to reach the alveolar spaces. Droplet nuclei can be produced when persons with upper and lower respiratory tract infections or with laryngeal infections speak, sneeze, cough, or sing. If these persons are in a healthcare setting such as a nursing home, and the diagnosis of tuberculosis, influenza A, or SARS is unknown, they become a risk to healthcare workers. Multidrug-resistant tuberculosis, SARS, and the 2009 H1N1 influenza A pandemic have refocused infection control efforts on airborne transmission of infection (56, 57 and 58). Consider, for example, the findings of a study investigating the potential for airborne distribution of influenza virus in an urgent care medical clinic (59). This study collected airborne particles from an Urgent Care Clinic using stationary National Institute for Occupational Safety and Health (NIOSH) 2-stage cyclone aerosol sampler. The presence of airborne influenza A, influenza B, and respiratory syncytial virus (RSV) was determined using real-time quantitative polymerase chain reaction (PCR). The results of this study demonstrated that airborne particles containing influenza and RSV RNA were detected throughout this healthcare facility. Moreover, these airborne particles were small enough to remain airborne for an extended period of time and to be inhaled deeply into the respiratory tract (59).

Clearly, airborne transmission of infection is important. Healthcare workers in laboratories are also at risk for airborne pathogens, because there are certain manipulations with patient samples that may produce an aerosol. An important example of such a manipulation is dropping of fluids containing microbial suspensions (e.g., urine containing M. tuberculosis microorganisms because of renal tuberculosis) onto a hard surface, producing an aerosol. Working with Neiserria meningitidis cultures is also considered a risk, and microbiology technologists should be immunized against this pathogen.

The risk of aerosolized M. tuberculosis from patients with unsuspected tuberculosis to posthospital healthcare workers such as home healthcare, nursing home, and clinic healthcare workers has become quite clear with the resurgence of tuberculosis in the United States. This risk increases in settings such as outpatient clinics where many sick people congregate in waiting and treatment rooms or halls and is also increased in communities where the incidence of HIV and/or tuberculosis is high. Outbreaks of tuberculosis among healthcare workers have occurred (60, 61 and 62); some have involved multidrug-resistant M. tuberculosis (61,62). This risk can best be appreciated by considering the tuberculosis skin test conversion rates among healthcare workers that have ranged from 0.11% to 10% (63,64). This risk increases considerably in healthcare workers who are exposed to persons from countries where tuberculosis is endemic, to HIV patients, and to patients known to have tuberculosis; the skin test conversion rates in such settings have ranged from 18% to 55% (65,66). Transmission of tuberculosis to healthcare workers can be a major problem requiring prevention and control (66). This problem is covered in great detail in Chapter 38.

A less well-appreciated, but equally important, risk for posthospital healthcare workers such as pathologists and funeral home workers is the risk for aerosolized transmission of infectious agents when working with deceased patients (67). In addition to the risk of dropping body fluids containing microbial suspensions, a number of other procedures associated with autopsies produce an aerosol. For example, the Rokitansky method, in which the abdominal and thoracic organs are eviscerated as a unit, continues to be commonly used at autopsy. However, this method involves blunt blind dissection in both cavities, which is cumbersome and creates unnecessary aerosols. The CLSI now recommends removing organs singly (the Virchow technique) to avoid the more hazardous aerosolization risk associated with complete evisceration by the Rokitansky method (19). The CLSI also recommends that organs not be photographed until they have been fixed in formalin to decrease the risk of aerosolized microorganisms. Unfortunately, this does not provide complete protection against aerosolized M. tuberculosis because this pathogen survives fixation in formalin, although the fixation does decrease the number of mycobacteria and thus lessens the degree of infectivity (68). The need to saw the calvarium is perhaps the most problematic autopsy procedure, because it unavoidably creates an aerosol. Aerosolization can be minimized by doing this procedure inside a plastic bag or plastic head frame, using a hand saw (difficult to do), or having a vacuum attached to the oscillating saw.

Another important risk factor for aerosolization during an autopsy is the use of side-arm faucet water aspirators to remove pleural or peritoneal fluids from these body cavities, because these aspirating devices produce an infectious aerosol. Side-arm faucet water suction devices should not be used in autopsy suites or in funeral homes. Instead, they should be replaced by surgical-type vacuum reservoirs that are attached to the hospital vacuum lines that have appropriate traps, filters, and regulators (69).

Air flow in the autopsy suites (but not funeral homes) has been addressed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers and by the CDC (17). Adequate air flow is an important means of minimizing the risk of aerosolized pathogens. Both groups recommend that autopsy suites have at least 12 total air exchanges per hour and that autopsy room air be exhausted directly to the outside. In addition, the College of American Pathologists recommends that autopsies on high-risk patients be done only in rooms with good ventilation (69,70).

It is important to have a clear understanding of what constitutes good ventilation. There are three important engineering factors that allow good ventilation/control of air within a room. First, negative pressure in the room should be maintained with respect to surrounding areas. This means that air should move from an area of low infectivity (i.e., outside the room) to an area of higher infectivity (i.e., inside the room). Second, the number of air changes in the room should be increased, which can substantially decrease the risk of the transmission of aerosolized pathogens by dilution and removal of these pathogens. Good ventilation also dictates that within-room mixing of air (i.e., ventilation efficiency) is adequate. This is usually accomplished by placing air supply outlets in the ceiling and exhaust inlets near the floor. This provides a downward movement of clean air, which travels through the breathing zone to the floor area for exhaust. Third, there should be adequate exhaust to the outside. Because the air in a high-risk room such as the autopsy suite is likely to be contaminated with infectious droplet nuclei, it should not be recirculated within the room or within the building. Instead, this potentially contaminated air should be exhausted to the outside, away from intake vents, people, and animals. An episode in a medical examiner’s office in Syracuse, New York, (62) illustrates this point. Two workers in the Onondaga County medical examiner’s office were infected by M. tuberculosis after they were exposed during autopsies on cadavers of prison inmates who had been infected with M. tuberculosis before death. In addition to the two workers who contracted clinical manifestations of tuberculosis, the tuberculin skin tests of 30% of the staff in the medical examiner’s office converted to positive; this included a secretary whose desk was right under the ventilation system that circulated air from the morgue. The examiner’s office responded to this episode by installing a new ventilation system, adding ultraviolet treatment of the air in the morgue, and initiating a respiratory protection program for personnel who worked in the morgue. Chapter 84 provides additional information on the design and maintenance of ventilation systems and prevention of airborne infections.

If adequate ventilation is not possible, healthcare workers who have any possibility of being exposed to aerosolized infectious particles should participate in a respiratory protection program. This is accomplished by wearing particulate respirators. A standard surgical mask is not a particulate respirator because lack of a tight face seal allows particles between 1 and 3 µm to be inhaled. Disposable particulate respirators are available. There are two types: the dust/mist filter, which excludes particles of 2 µm, and the fume filter, which excludes particles 0.6 to 1.0 µm. The CDC has published guidelines for the use of particulate respirators that include training, fit testing, care, and maintenance (17); OSHA requires that a fume filter be used in particulate respirators (18).

It is well appreciated today that exposure to blood or body fluids via direct contact or inoculation can result in the transmission of a number of pathogens, of which the best known examples are hepatitis B virus (HBV) and HIV. The risk of HIV has increased the awareness of this problem. Numerous incidents of exposure of healthcare workers to HIV-infected blood have been evaluated in multiple prospective studies. These studies have identified HIV infections, usually involving individuals who had been punctured with needles; seroconversions are rare in staff members with intact skin. The rate of infection with HIV in healthcare workers after exposure to HIV-infected blood is approximately 0.3% (71). It is instructive to review these seroconversions in healthcare workers analyzed by the CDC (71), including six from prospective studies. Of the 34 individuals with
seroconversion, 12 were nurses, 11 were laboratory workers, 4 were physicians, and the other 7 were from other occupational groups. All underwent HIV seroconversion within 1 year of exposure, which had been mucocutaneous contact or percutaneous inoculation with blood or fluids containing HIV. Of the 28 percutaneous inoculations, 14 occurred while drawing venous blood and 2 occurred while drawing arterial blood; 5 of these were associated with carrying out intravenous infusions. Of the remaining injuries, two had occurred while injecting laboratory specimens, one while holding a specimen vial and two while manipulating a transvenous pacemaker. The remaining injuries were a result of other or unknown causes. Most of these percutaneous inoculations occurred after unexpected movement by a patient, a coworker, or equipment (seven exposures); inadequate needle disposal (nine exposures); and recapping of needles (seven exposures). Thirteen of these twenty-eight occurred through the workers’ gloved hands. Of the five mucocutaneous exposures that resulted in seroconversion, one involved pressure hemostasis with an ungloved hand, three occurred during accidents involving blood spillage, and one involved an individual who was sprayed with concentrated virus. The CDC has concluded that the most frequent cause of occupational transmission of HIV or HBV is injury by a needle contaminated with the virus (71). However, other mechanisms such as virus-contaminated body fluids being splashed on mucosal membranes and, to a lesser degree, skin clearly are important. Finally, but most importantly, postexposure prophylaxis with antiretroviral therapy with zidovudine (ZDV) has been found to be associated with a >80% reduction in the risk of occupational infection (72). Prophylaxis clearly is important (73,74). For this reason, the PHS recommends that ZDV, lamivudine, and sometimes a protease inhibitor such as indinavir should be given prophylactically within 1 to 2 hours of a high-risk exposure to HIV (74) (see also Chapter 74).

HIV-1, as already mentioned, is responsible for altering the approach to prevention of occupational exposure to infectious agents in the healthcare workplace (130). Mechanisms for transmission of HIV-1 to posthospital healthcare workers include direct contact (e.g., splashing mucosal surfaces) and inoculation. To date, there is no evidence for airborne transmission or fecal-oral transmission. Obviously, the posthospital healthcare workers at risk include all those involved with blood and body fluids of premortem or postmortem AIDS victims and the trash haulers and landfill operators who may be exposed to improperly disposed needles. The key to prevention of HIV-1 infections in these persons is to prevent exposure. A number of these preventive measures were discussed previously in this chapter.

Additional measures include decontaminating any spills of blood or body fluids in the work area with 5% sodium hypochlorite. All instruments used for AIDS patient care should be soaked in disinfectant for 30 minutes before routine washing. HIV-1 is inactivated by a wide range of disinfectants (131,132), including 50% ethanol, 3% hydrogen peroxide, phenolic compounds (e.g., Lysol), iodophor compounds (e.g., Betadine), and sodium hypochlorite (household bleach) in a freshly prepared 1:10 dilution in water (final concentration: 0.5%). Because of their corrosive action, soaking instruments in bleach solutions should be limited to 30 minutes. Instruments using electronic devices that are an integral part of the equipment are more difficult to disinfect (133). Fortunately, studies have shown that HIV-1 is reliably eliminated by routine disinfection for such electronic instruments (134). In addition, there are now guidelines for disinfection practices for semicritical items (135) (see Chapter 80).