Rationale: Although the manifestation of severe pneumonia and hypotension is not common, it can be due to typical bacterial pneumonia. However, atypical bacterial pneumonia and other unusual zoonotic infections (e.g., tularemia, plague, RMSF) should also be considered. Meningococcemia may manifest with hypotension, but lobar pneumonia is uncommon. Mycoplasma, Chlamydia, and Q fever do not generally cause hypotension. Although adenovirus may cause severe pneumonia, other viruses, such as the SARS-CoV, hantavirus, or dengue hemorrhagic viruses, would be more likely. These would be expected to be seen in certain geographic areas or with specific exposures.