RIVERSIDE, Calif. - Seven southwestern states have wood rats carrying the rare arenavirus, which has been linked to three deaths in California.
Arenavirus typically is associated with wild wood rats and believed to be transmitted to humans in dust carrying an infected rodent's urine, feces or saliva, a health expert said Friday.
Arenavirus is believed to have killed a 14-year-old Oakland girl, who died in April; and a 30-year-old Orange County woman and a 52-year-old Riverside County woman in the past 14 months.
Charles Fulhorst, a researcher at the University of Texas Medical Branch who helped California health officials tie arenavirus to the deaths, said the virus is a great risk and health officials must alert the public.
''The human population at risk of infection is not just the local population in California - it far exceeds that,'' he said Friday.
Field studies have found arenavirus in rats in Arizona, California, Colorado, New Mexico, Oklahoma, Texas and Utah. The California deaths are the first North American cases in which humans have contracted the virus.
California health officials asked Fulhorst to check samples from 20 people who died of unexplained causes. Only three were caused by arenavirus.
It is unknown specifically where the victims, who all were hospitalized with fever and respiratory problems, acquired the virus.
State officials are planning to expand rodent trapping to determine how widespread arenavirus is. Most of the trapping so far has been done in Southern California, particularly the Santa Ana Mountains straddling Riverside and Orange counties, and an area east of Hemet in Riverside County.
California officials believe there is only a slim risk of humans contracting the virus, especially if people take precautions.
Also, investigators with the federal Centers for Disease Control in Atlanta are trying to organize a meeting with health officers from other southwest states to discuss the virus, Fulhorst said.