Respiratory viruses, other than influenza viruses, are becoming increasingly recognized as the etiology of severe pneumonia requiring admission to the critical care unit.

The most frequent causes of this type of pneumonia are rhinoviruses, respiratory syncytial virus, parainfluenza, human metapneumovirus, and coronaviruses. Severe acute respiratory syndrome virus and Middle East respiratory syndrome virus have appeared following zoonotic and then person-to-person transmission and disappeared, perhaps to reappear. Hantavirus has caused seasonal severe pneumonia predominately in Western North America.

There are several viruses that are lesser common causes of severe pneumonia in critical care units—these are cytomegalovirus, herpes simplex virus, varicella-zoster virus, Epstein Barr virus, enteroviruses, measles virus, mimivirus, and bocavirus.

Multiplex real-time polymerase chain reaction is the diagnostic test of choice.

In the absence of effective chemotherapeutic agents, supportive care is the mainstay of treatment. Prevention of secondary spread using optimal infection control procedures is key to containing such infections in the critical care unit.