Epidemiology
Case Characteristics
For the latest counts and descriptive statistics on confirmed cases
of HPS in the United States, please see the HPS
Case Information page. Information on this page is updated as
the case count changes.
HPS an 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 (see Tracking
a Mystery 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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