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Common Settings for Hantavirus Exposure in the United States Revealed

A new study from the Centers for Disease Control and Prevention has shown American Indians in the Four Corners region of the United States are disproportionately affected by the hantavirus.

A recent study examined exposure characteristics of hantavirus pulmonary syndrome (HPS) over a 22-year period, showing that the syndrome disproportionately affects American Indians. Certain types of jobs also increase an individual’s risk of acquiring HPS.

Annabelle de St. Maurice, MD, MPH, from the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and colleagues published the results of their study in the May 2017 issue of Emerging Infectious Diseases, CDC’s monthly peer-reviewed public health journal.

“Although HPS is rare in the United States, surveillance data suggest that persons in certain occupations and certain populations may be at increased risk for HPS because of potential for rodent exposure,” the authors write.

Hantavirus pulmonary syndrome is a severe respiratory disease caused by hantavirus. The virus is spread to humans through contact (via inhalation or ingestion) with rodent droppings, urine, or saliva. Only 20 to 40 cases of HPS occur in the United States each year, but the syndrome can be fatal.

“In the United States, most HPS cases are caused by Sin Nombre virus, for which the North American deer mouse (Peromyscus maniculatus) serves as reservoir,” the authors say.

People are known to be at increased risk for developing HPS if they live in a rodent-infested home, handle rodents, or clean rodent-infested areas.

With this in mind, Dr. de St. Maurice and colleagues conducted a study to further investigate demographics of HPS case-patients and to identify the types of exposures that could potentially increase a person’s risk for HPS.

The researchers analyzed national surveillance system data, assessing demographics and rodent exposure settings for 662 case-patients from 1993 to 2015. They found that the risk for HPS was higher for people in certain populations, locations, or occupations. Among 651 of the patients for whom outcome information was available, 230 (35%) died.

According to the authors, American Indians represent approximately 2% of the US population, yet accounted for 18% of the reported HPS cases in their study, with most (78%) cases arising in white patients. American Indians with HPS were also significantly younger than white patients with the condition (mean age 34 years vs 39 years), and had significantly higher mortality rates (46% vs 33%). Mortality rates were also significantly higher among American Indian women aged 40 to 64 years than among white women of the same age group, the authors note.

Among 319 individuals for whom rodent exposure was recorded, 71% reported exposures in the home, 32% reported exposures at work, and 24% reported exposures in a recreational setting.

The researchers found that home exposure occurred more commonly among those living in the western United States than among those in the eastern United States (73% vs 47%). Interestingly, the proportion of home exposures was also significantly higher among American Indians than among whites (86% vs 71%).

The authors note that 89% of American Indian HPS case-patients lived in the Four Corners region where most HPS cases occur. Consequently, the authors suggest that environmental factors that increase the risk of inhaling infected dust particles may contribute to the disproportionate number of cases of HPS in American Indians found in this study.

In contrast, recreational exposure occurred more commonly among those living in the eastern United States (47% vs 23%) United States. The proportion of occupational exposures was similar in eastern and western regions (35% vs 32%).

However, the researchers did find that people working in jobs for which frequent rodent contact was possible were more likely to experience occupational exposure than those in jobs without potential risk for rodent contact (such as teaching or clerical work). “Of those whose exposure was work related, 53% had jobs with potential risk for rodent exposure,” the authors write. Reported occupations that were associated with increased risk for rodent exposure included agriculture, construction, and forestry/outdoor recreation.

The authors emphasized that clinicians should be aware of risk factors for HPS and must consider HPS as a differential diagnosis for patients who have had contact with rodents, as well as for those who have a high risk for rodent exposure. “Educational efforts and awareness focused on high-risk populations should continue so that persons can decrease their risk of acquiring HPS,” Dr. de St. Maurice concludes.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.