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Seriously sick. Normal (top) and Andes virus-infected lung tissue from the Syrian hamster.

A Handle on Hantaviruses

A group of U.S. Army virologists has found by accident what researchers had been seeking for decades: an animal model to study hantaviruses, a fearsome group of rodent-borne pathogens. In a paper accepted by Virology, they report that Syrian hamsters get sick and die when injected with a hantavirus from South America. Their disease looks strikingly like hantavirus pulmonary syndrome (HPS), a lethal manifestation of the infection in humans.

The hantavirus family grabbed world headlines in 1993 when an outbreak occurred in the Four Corners area in the southwestern United States. The culprit, now called Sin Nombre virus, is one of several hantaviruses that cause HPS throughout the Americas. In Europe and Asia, a quartet of hantaviruses has long been known to cause a different disease called hemorrhagic fever with renal syndrome (HFRS). The U.S. Army has had a keen interest in developing hantavirus vaccines ever since HFRS hit United Nations troops hard during the Korean War.

But there was a constant handicap: the lack of animal models. Because of this obstacle, researchers couldn't test whether a vaccine keeps animals from getting sick. Instead, they had to test whether it could prevent infection altogether--a much stricter test, because it flunks vaccines that let the virus enter the body and replicate but that prevent illness.

A team at the U.S. Army Medical Research Institute of Infectious Diseases in Fort Detrick, Maryland, recently started looking into vaccines for Sin Nombre and the Andes virus from South America. A key initial step was determining how much virus is needed to infect an unvaccinated animal. When team leader Jay Hooper injected hamsters with Sin Nombre, they got infected but stayed healthy. But some 11 days after he injected adult Syrian hamsters with Andes virus--a combination nobody had ever tired before--something unusual happened: The animals got sick, and most died within days--just as fast as human HPS victims. Further studies revealed that most of their symptoms closely resemble HPS in humans.

Not only do researchers now have a better way to test vaccines and drugs, but they can also study the details of hantavirus pathogenesis. "I'm impressed," says Heinz Feldmann, a virologist at the Canadian Science Centre for Human and Animal Health in Winnipeg. Virologist Stuart Nichol of the U.S. Centers for Disease Control and Prevention in Atlanta hails the study as "a major breakthrough for the field."

Related sites

Paper about the global burden from hantaviruses, in Emerging Infectious Disease
Hantavirus information from the Centers for Disease Control and Prevention
The U.S. Army Medical Research Institute of Infectious Diseases