Officials Try to Calm Fears Over Hantavirus Find : Disease: Vector and health experts say, however, that more scientific study is needed to determine if it is a health threat.

The discovery that a mysterious, often fatal virus spread by rodents is present in Orange County prompted hundreds of anxious calls to county pest control and health officials Wednesday.

County and state health officials sought to calm the public’s jitters about the airborne hantavirus, saying stepped-up scientific study is needed to determine whether there is a public health threat.

“It’s been extremely hectic,” county vector ecologist Jim Webb said Wednesday. “There have been a lot of calls from residents in and around San Clemente who are worried about the danger. We’ve been telling them the safety precautions to take.”

The hantavirus, suspected in the deaths of at least 33 people nationwide, was detected among stored blood samples taken last year from five deer mice trapped in a canyon near San Clemente, a county scientist announced Tuesday.

The finding may indicate the local presence of the same virus that has claimed lives in eight states. But scientists cautioned that because the virus has not been isolated, it is impossible to know yet whether it is dangerous or perhaps a weaker version of the deadly strain.

State public health biologist Jim Clover said Wednesday that additional trappings have been halted until precautions are put into place to protect field workers who come in contact with the rodents.

However, Clover said that lab work, not field work, is now the key to isolating, identifying and defeating the hantavirus.

“It’s not a matter of just going out and making gestures, we want to do something substantial,” he said from his Sacramento laboratory. “We’re doing things from here.”

The eight-member staff in Clover’s office has already undergone three weeks of training with experts from the Centers for Disease Control and Prevention in Atlanta and the Army to devise safety measures for future field research.

“This is a new experience for everybody, so there are new guidelines forming weekly,” Clover said. “We’re not geared up to go out there and do things yet. There is some (decontamination) equipment we don’t have yet.”

Gaps in the knowledge about the virus leave health officials in the dark about the significance of five virus carriers found in the rural Orange County canyon.

“What we need to find out is the background,” Clover said. “Maybe what they found in Orange County they will find anywhere, it may be perfectly normal.”

Two California deaths, the nearest in Santa Barbara County, have been linked to the virus, which is transmitted via the airborne fine dust emitted from deer mice droppings.

State epidemiologist Ben Werner said rodent blood samples from throughout the state are being scanned for antibodies that signal presence of the virus to “get a handle on where it is.”

Although the Orange County mice that tested positive for antibodies created by the virus were captured last year, officials stress that no cases have been documented in Orange County of the hantavirus illness, which initially strikes with flu symptoms but rapidly worsens.

It is possible, Webb said, that the positive test results could indicate a different, less dangerous relative of the virus.

Health officials advise the public to avoid contact with the deer mouse and other rural rodents, and to dampen any droppings with a bleach-and-water mist before wiping them up. They also recommend wearing gloves and using plastic bags for disposal.

Those measures, along with other information about the hantavirus, will be presented Friday in a meeting with more than 100 employees of the 2,770-acre TRW Capistrano Test Site, a sprawling facility located several hundred yards from the trap location.

“Basically we’re going to talk, I believe, with the rank-and-file employees and some bigwigs and let them know about what they are dealing with,” Webb said. “Just so they are aware.”

A company memo about the situation has been sent to employees at the high-security facility, which researches and develops technology in areas such as directed energy, propulsion and space communication, said Susan Brough, a spokeswoman for TRW Space & Electronics Group.

TRW employees were reluctant to comment Wednesday, but one man told a reporter that workers have heard about the findings and “don’t seem overly concerned.”

The relatively obscure but often deadly family of hantavirus was first recognized among U.S. and U.N. troops deployed in the Korean War, when several hundred soldiers fell victim to flulike symptoms, kidney damage and death.

The hantavirus was first isolated and named in 1976 by a virologist at the Korea University in Seoul, and the same scientist, Ho Wang Lee, discovered a different strain of the same virus in common Norwegian rats in the early 1980s. In all, eight strains of the virus, considered a significant public health threat worldwide, were identified before last year.

The virus that was first noted during a rash of deaths in the Four Corners area of Utah, Colorado, New Mexico and Arizona, likely will become the ninth strain isolated, scientists said.

The alarming report of a hantavirus death last month in Louisiana--which lies outside the range of the deer mouse--hints that a 10th strain carried by a different rodent species may be lurking, according to experts.

The Orange County mice blood samples were collected during a population study related to the county’s ongoing monitoring of Lyme disease. That survey, begun in 1989, was halted last month after state health officials recommended that all rodent field studies cease until safety procedures could be devised.

Stored in a freezer for months, the 153 vials of blood from various species collected countywide were shipped off last month to the federal Centers for Disease Control to provide a snapshot of Orange County’s hantavirus situation.

Five of the 13 samples taken from Talega Canyon near Avenida Pico yielded a positive result, and Webb said one of the deer mice that had tainted blood is still in a freezer at the county Vector Control District’s Garden Grove facility. He said the animal would be shipped to the Centers for Disease Control this week.

An advisory from the state Department of Health Services also notes that the two California fatalities, one in the Mammoth Lakes area of the Eastern Sierra and the other in Santa Barbara County, both occurred among people who had “prolonged and direct contact with wild rodents.”

“Human disease from this infection is exceedingly rare, even in people with considerable rodent exposure,” the advisory states. When the virus does strike, however, its fatality rate may reach or exceed 75%, Webb said.

Times staff writer Len Hall and correspondent Anna Cekola contributed to this report.