BACKGROUND: Hantavirus is a rodent-associated human pathogen that can cause Hantavirus Pulmonary Syndrome (HPS), a severe respiratory illness with a 38% case fatality rate. Hantavirus infection is rare in Indiana, with only two cases reported from 1993–2014. While occupational exposure to wild rodents is a theoretical risk for hantavirus infection, previous serosurveys of people with such exposures revealed low seroconversion rates (≤0.5%). The Indiana State Department of Health (ISDH) was notified of positive commercial laboratory test results for hantavirus in two university students in the same wildlife ecology laboratory in July 2015 and May 2016.
METHODS: Medical records were reviewed to obtain clinical information. Both patients were interviewed to identify risk factors for hantavirus exposure. Acute and convalescent specimens were tested by RT-PCR and IgM and IgG enzyme-linked immunosorbent assay (ELISA) at the Centers for Disease Control and Prevention (CDC). The wildlife ecology laboratory’s research protocols were audited and reviewed for potential occupational risk factors.
RESULTS: Patient A presented with HPS requiring hospitalization, but survived. Patient B presented with mild influenza-like illness and did not require hospitalization. Patient A had both field and laboratory exposure to deer mice and white-footed mice, while patient B had only field exposure to these species. Both patients reported inconsistent use of personal protective equipment (PPE) and being bitten and scratched by mice while performing research activities. Both patients had laboratory evidence for hantavirus by RT-PCR, IgM ELISA, and IgG ELISA when tested at CDC. The university had a standard operating procedure (SOP) for handling rodents in the laboratory, but did not have one for handling rodents in the field.
CONCLUSIONS: The two cases in this investigation represent a two-fold increase in Indiana’s all-time hantavirus case count in a one-year period. The occurrence of two cases in the same occupational setting is unexpected, given the low rate of seroconversion in comparable populations. The ISDH provided interim recommendations for the prevention of hantavirus infection among workers in the wildlife ecology laboratory, including specific recommendations for handling rodents in the field. Universities and other research institutions that perform field and laboratory work with wild rodents should ensure that proper safety measures are followed by students and staff in order to avoid occupational exposures to hantavirus. The ISDH will conduct a serosurvey of other workers in the same laboratory in early 2017 to identify risk factors for seroconversion and develop further recommendations for prevention of hantavirus infection in this population.