A virus discovered in rodents 4 years ago has now killed at least one person and possibly others. Today, California's Department of Health Services said lab tests have confirmed that the Whitewater Arroyo virus killed a 14-year-old girl in April. It's also strongly suspected to have killed two other Californians over the last 14 months. Even so, "people don't need to be alarmed," says Carol Glaser, an infectious-disease physician at the state's Viral and Rickettsial Disease Laboratory. "We think this is a rare event."
The new virus belongs to the arenaviruses, a group that includes Lassa fever in Africa and several deadly hemorrhagic fevers in South America. Like the hantaviruses, arenaviruses spread to people when they inhale dust that contains urine, feces, or saliva from infected rodents. In 1996, Charles Fulhorst of the University of Texas Medical Branch (UTMB) in Galveston and his colleagues discovered that a new arenavirus was widespread in wood rats in several western U.S. states. They named it the Whitewater Arroyo virus, after the New Mexico site where it was discovered. What they didn't know was whether the virus could sicken humans.
Now their fears have been confirmed. Recently, Glaser has been sending Fulhorst blood samples from patients who died with undiagnosed, arenaviruslike symptoms, such as encephalitis and bleeding. Fulhorst says he found antibodies to the Whitewater Arroyo virus, as well as traces of its genetic material, in a patient from Riverside County, east of Los Angeles, who died in June last year. These clues also turned up in another patient from Orange County who died 2 months ago. In samples from the 14-year-old girl from Alameda County in Northern California, his team isolated the virus itself--definitive proof that it was the culprit, Fulhorst says.
Fulhorst is working on a rapid test to detect arenavirus infections. Such a test might help future patients, Glaser says, because they could be treated with a drug called ribavirin, which fights other arenaviruses. Robert Tesh, a colleague of Fulhorst's at UTMB who studies arenaviruses in South America, says early detection may have yet another benefit. Unlike hantaviruses, arenaviruses can infect doctors and nurses who come into contact with patients' blood. If new cases are identified early, doctors could treat patients with extra caution, Tesh says.