Hantavirus Pulmonar Syndrome: A Zebra Worth Knowing -- American Family Physician

www.aafp.org/afp AMERICAN FAMILY PHYSICIAN 1015 omyscus maniculatus), one of the most common small mammals in the United States. Additionally, the cotton rat and rice rat are the rodent vectors in the southeastern United States for the Black Creek Canal and Bayou viruses, respectively; the whitefooted mouse carries the New York virus in the northeast. Before 1993, illness caused by hantaviral infection had never been documented in the Americas. In Europe and Asia, infection with hantaviruses was known to cause hemorrhagic fever with renal syndrome (HFRS), an entity clinically distinct from HPS. HFRS lacks the severe pulmonary involvement characteristic of HPS and instead exhibits coagulaopathies and renal manifestations not usually seen in HPS. Since the initial outbreak in the United States, there have been more than 280 confirmed cases of HPS, representing approximately 30 cases per year. Contrary to common opinion, HPS is not limited to the southwestern United States and has been reported in 31 states (Figure 1), as well as in Canada and South America. This expanding geographic distribution is largely because of increased H antavirus pulmonary syndrome (HPS) was first recognized during the spring of 1993 after a cluster of young, previously healthy individuals who lived in the southwestern United States acquired an acute, fatal cardiopulmonary illness. The early nonspecific symptoms of these patients uniformly resembled those of other more frequently seen benign viral infections, so the severity of these infections was not initially suspected. However, the febrile prodrome was followed by rapid, diffuse, noncardiogenic pulmonary edema and hemodynamic compromise resulting in an initial case fatality rate of 76 percent. The etiologic agent was subsequently determined to be a previously unrecognized hantavirus, Sin Nombre virus (SNV), and is now known to be the predominant cause of HPS in the United States. Currently, at least eight species of hantavirus are known to cause HPS in the Western Hemisphere, four of which are found in the United States. Each different virus is associated with a single rodent host species; the reservoir for SNV is the deer mouse (PerHantavirus pulmonary syndrome (HPS) is a severe cardiopulmonary illness most often caused by the Sin Nombre virus, which is transmitted to humans by inhalation of aerosolized particles of rodent excreta or direct rodent contact. Although HPS is more common in the western United States, cases have been identified in 31 states. The illness begins as a nonspecific febrile prodrome, sharing many of its initial symptoms with other more common viral infections. Patients then quickly develop noncardiogenic pulmonary edema, respiratory failure, and shock. Characteristic laboratory findings include thrombocytopenia, a left-shifted leukocytosis, hemoconcentration, and presence of immunoblasts. The overall case fatality rate of HPS is approximately 40 percent. Diagnosis is confirmed by serologic identification of IgM and IgG antibodies to Sin Nombre virus. There is no specific therapy, but early recognition of HPS during the prodromal phase can expedite initiating cardiopulmonary support in an intensive care unit, which is associated with improved survival rates. Prevention of HPS involves avoiding contact with rodents and rodent habitats. (Am Fam Physician 2002; 66:1015-20. Copyright© 2002 American Academy of Family Physicians.) Hantavirus Pulmonary Syndrome: A Zebra Worth Knowing