Case Characteristics

For the latest counts and descriptive statistics on confirmed cases of HPS in the United States, please see the Case Reports page. Information on this page is updated as the case count changes.

HPS: Old Disease, Newly Recognized

Although the high-profile investigation of the HPS syndrome emphasized public health authorities’ warnings about new and emerging infectious diseases, HPS has turned out to be a newly identified, but not a “new”, disease. In fact, the earliest case of a serologically confirmed SNV infection was in a person who developed an HPS-compatible illness in July 1959 and was found to have IgG antibodies in September 1994. The earliest case of HPS to be confirmed by IHC with direct visualization of hantaviral antigens in postmortem tissue involved a patient who died in 1978.

Risk Factors for Disease

Little is known about activities that lead to a greater risk of infection. However, an early case-control study suggests that increased numbers of rodents in the household is the strongest risk factor for infection. Entering rarely opened or seasonally closed buildings may also contribute to infection. Among the confirmed cases of HPS for which exposure information is available, 70% of the patients in the case control study had exposures closely associated with peridomestic activities, such as cleaning, in homes that showed signs of rodent infestation. Four clusters of HPS cases involving 2-4 persons have been documented; for each cluster, exposure probably occurred within a shared, enclosed structure. Taken together, these observations suggest that disturbing or inhabiting closed, actively rodent-infested structures may constitute an important risk factor for contracting HPS.

Potentially occupationally acquired SNV infections have been recognized but are infrequent. Among documented U.S. cases of HPS, patients with potential occupational exposures have included grain farmers, an extension livestock specialist, field biologists, and agricultural, mill, construction, utility and feedlot workers. Many of these individuals had concurrent peridomestic exposures. Among U.S. mammalogists and rodent workers with varying degrees of rodent exposure, the seroprevalence of SNV antibodies was 1.14%. In contrast, a recent HPS seroprevalence study focused on selected occupational groups with frequent contact with rodents and their excreta (e.g., farm workers, laborers, professionals, home repairers, service industry and park service workers, heating and plumbing contractors, utility workers, and technicians) found no evidence of SNV infection.

Travel to and within all areas where hantavirus infection has been reported is not considered a risk factor for infection with HPS. The possibility of exposure to hantavirus for campers, hikers, and tourists is very small and is reduced further if steps are taken to reduce rodent contact.

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