Arenavirus Infection Linked to Deaths in California.

Three deaths in California have been linked to a virus in the genus Arenavirus. This rare virus has never before infected humans in North America. The discovery followed an extensive investigation by the California Department of Health Services (DHS) and the University of Texas Medical Branch (UTMB) into the unexplained deaths of a 52-year-old woman who died in June 1999 in Riverside County, a 14-year-old girl who died in April 2000 in Alameda County, and a 30-year-old woman who died in June 2000 in Orange County. UTMB has one of the few laboratories in the coun try equipped to test for arenaviruses.

The virus was detected in all three patients through testing for virus genes. In addition, virus isolation was used to confirm infection in the 14-year-old victim. Further testing is under way. Each of the three individuals was hospitalized with fever and respiratory distress. Two of them also had severe liver disease and bleeding consistent with a viral hemorrhagic fever. There is no evidence that the three cases are related.

Like hantaviruses, which cause a rare, but often fatal, respiratory disease, arenaviruses are believed to be transmitted to humans through inhalation of dust contaminated with the urine, feces, or saliva of infected rodents. Human infection with an arenavirus is likely to be very uncommon. Arenavirus infection has, however, been documented in rodents in Southern California in recent years.

"Viral hemorrhagic fever associated with arenaviruses has never been documented in the United States except among overseas travelers and laboratory personnel exposed accidentally while doing research," said California State Health Director Diana M. Bonta, R.N., Dr. P.H. DHS was prompted to send specimens to UTMB because of clinical and autopsy findings suggestive of viral hemorrhagic fever and because of a history of rodent contact in the Riverside County patient.

In parts of Africa and South America, several arenaviruses are known to cause mild to severe infection characterized by fever, headache, and occasionally severe bleeding or nervous-system problems. Lassa fever and the South American viral hemorrhagic fevers are examples of human illnesses caused by such arenaviruses.

The antiviral drug ribavirin has been successfully used in the treatment of other arenavirus infections. Studies are under way to learn more about this virus and to identify medicines that may be effective. People can protect themselves from diseases carried by rodents by taking relatively simple precautions both in the home and while outdoors:

* Do not touch or feed wild rodents or any other wild animals.

* Properly dispose of trash and clutter; move woodpiles away from residences.

* Prevent rodents from entering residences by blocking holes; control rodents with spring-loaded (snap) traps.

* Store food and garbage in rodent-proof containers; pet food should not be left outside.

* Avoid creating dust when cleaning buildings with signs of rodent infestation. Wet the area thoroughly with a disinfectant such as bleach and use gloves to clean up.

* Contact local public health officials for recommendations about safely cleaning rodent-infested areas.

* Cabins and buildings that haven't been occupied for some time should be aired out. If there are signs of rodent infestation, buildings should not be used, if possible, until properly cleaned.

* When sleeping outdoors, avoid campsites near rodent droppings, burrows, or nests.