County officials said Tuesday that a strain of the dangerous hantavirus has been discovered in a roof rat, the type of rodent that has invaded thousands of homes and apartments across Southern California.
No illnesses related to the so-called Seoul virus have been reported, but the virus can cause kidney failure in extreme cases. The strain is rarely fatal, said Dr. James Webb of the Orange County Vector Control District.
The county is urging residents who notice roof rats on their property to call the vector control office, which will dispatch a crew to determine whether the rodents are carrying the virus or any other disease.
Officials estimate that hundreds of thousands of roof rats live in Orange County, mostly in the South County area. Complaints of rat problems increased 30% in the first four months of this year compared to the same period in 1998.
The upswing is blamed on El Nino, which brought record downpours to the Southland last winter and swelled the animal populations that thrive on the lush vegetation created by the stormy season.
The infected rat was discovered in December at the Villa Park Flood Control Basin in Orange. It took nearly eight months to confirm that the rodent carried the Seoul virus, Webb said.
The public should always be wary of rats because they often carry diseases such as bubonic plague and salmonella, he added.
"From Day One: If you have a rat problem, get rid of them," Webb said. "The rat is a bad guy in this game, and we need to get rid of them."
But removing the rodents is harder than it sounds.
The Vector Control District recommends that residents take safety precautions when removing rodent carcasses or droppings.
Both the droppings and carcasses should be misted from above with a mixture of one part household bleach and nine parts water. The items should then be placed in a double plastic bag before being thrown away.
Furthermore, droppings should never be swept or handled because of the possibility that residents could inhale particles.
Officials believe this is the first strain of the Seoul virus found in Southern California. It was reported in San Francisco more than 15 years ago, Webb said. It has also been noted sporadically on the East Coast.
"It's not too common a disease in the U.S., and it's up to us to keep it that way," Webb said.
Those who suffer from the virus will first experience flu-like symptoms, including a fever and headache. After that, splotchy rashes will appear on the skin. From there, more severe symptoms like kidney failure may occur.
A doctor should be sought once the rashes appear, Webb said. Though there is no cure, antiviral medicine can alleviate the symptoms.
Meanwhile, the Vector Control District is trying to trap more rats throughout the county to determine how widespread the disease is, Webb said.
Over the next few months, the district will expand its hantavirus surveillance program, in which rodents' blood is tested for numerous diseases, Webb said.
Since a different form of the hantavirus was found in the San Clemente area in 1993, the county has tested more than 2,400 rodents, Webb said.
Kevin Reilly, an epidemiologist with the California Department of Health Services, said the key for residents is to keep rodents out of the house by removing any water or food lying around and by closing any cracks in the walls.
Rats "live their lives in the wild," Reilly said. "We live ours in our households. Let's not mix the two."
Times staff writer Ioana Patringenaru contributed to this report.