By Anna Roys Domalewski

In the last week both the Center for Disease Control (CDC) and World Health Organization (WHO) have posted information on official websites about an ongoing multi-state outbreak of Seoul virus in the United States. These postings follow the release of information by multiple local news sources in affected states featuring information about the outbreak in Norway rats (Rattus norvegicusa), a common type of pet rat and often found in large urban areas.

Seoul virus is a type of Hantavirus that is rare in humans but can still have potentially lethal effects. It is spread from animal to human when rat waste (urine or feces) becomes aerosolized and inhaled into the lungs. A human Seoul virus infection can result in flu like symptoms and rash, and in some cases can lead to Hemorrhagic Fever with Renal Syndrome (HFRS), which can be lethal. Seoul virus is not known to be transmitted from person to person.

As of February 16, the CDC has detected Seoul virus in 16 states and continues to investigate 13 lab-confirmed human cases in 8 states. Public health officials believe that the source of the outbreak can be traced back to rat breeding facilities for both laboratory rats and potentially home pet rats. It is believed that biting and aggressive behavior rapidly spreads Seoul virus among rat populations, especially those that are kept in high quantities in small spaces.

Depopulation and other control measures are being taken in facilities with suspected and confirmed cases of Seoul virus across the country, as well as in homes with pet rats that are believed to have the virus. In one case, a Chicago-area woman was forced to euthanize all 31 of her pet rats because one was likely bought from an infected facility. Three cases in New York City were traced to a residential building with a rat infestation in the basement.

Although rats do not actually exhibit symptoms of Seoul virus and a human death only occurs in 1-2% of cases, managing and limiting the spread of the virus is crucial. CDC officials and members of state public health departments continue to encourage limiting contact with rodents that may be infected, safely cleaning and disposing of rat waste, and possibly getting pet rats tested for Seoul virus to prevent further spread.