If you haven't done so already, now would be an opportune time to throw some bug dope in with your garden tools. There's still a lot of growing and harvesting to do and it comes when biting insects are at their most annoying -- and most dangerous.

Most West Nile virus outbreaks are reported from mid-August through autumn and don't decline until the first killing frost, according to the U.S. Centers for Disease Control and Prevention, which recommends using insect repellents to help minimize the risk.

West Nile virus is not a disease transmitted from person to person. Instead, mosquitoes become infected after feeding on the blood of birds or other animals carrying the virus. They spread the disease to humans with their bite, which becomes most potent in early fall. That's why the disease rate climbs so rapidly through the period.

As of this week, about a dozen people this year have been stricken by the virus in San Diego County. Dozens of dead birds and a handful of horses also have tested positive for the disease, according to the county's Health and Human Services Department.

The recent cases involve patients from San Diego and East County. None are from North County. The patients range from 8 to 85 years old.

West Nile virus was first detected in the Western Hemisphere in New York City in 1999. It since has spread to the 48 contiguous states, Canada, Mexico and the Caribbean. The degree of severity ranges from mild to deadly. People over age 50, along with those having lowered immune systems caused by such things as HIV or cancer therapy, are the most susceptible.

Health officials have warned for several years that the virus, which showed up on the East Coast in 1999 and has been moving west, would eventually infect large numbers of Southern Californians. Until this summer, the virus had infected dozens of animals but relatively few humans.

About one in every five people infected with the West Nile virus develops symptoms including headaches, fever, fatigue, nausea and a skin rash. About one in every 150 cases results in a severe illness that can cause muscle weakness, a stiff neck, confusion and coma or paralysis.

In a few cases, West Nile encephalitis leads to brain damage and death.

Nearly 4,300 West Nile cases were reported around the nation last year, with about 1,500 of them having illnesses that had advanced to the encephalitis, meningitis or paralysis stages. One hundred and seventy-seven died, the CDC said.

"The chances of coming down with the disease are much higher than zero," said Emily Zielinski-Gutierrez, a behavioral scientist with the CDC's Division of Vector Borne Infectious Diseases in Fort Collins, Colo.

"Despite that, only 40 percent of the people responding to our surveys say they use insect repellents 'always,' 'often' or 'regularly.' That figure usually goes up a little bit during outbreak periods."

Most simply say they forgot their repellent when they stepped outdoors, she said. "They went outside to deadhead in the garden and got distracted. Or it wasn't convenient when it was needed. It only takes one bite."

Mosquitoes generally rank No. 1 on every gardener's bite parade, but humans are prey animals for other insects, too, including black flies (gnats), deer flies, chiggers, no-see-ums, yellow jackets and wasps and ticks.

Some people are targeted more often than others; you may be forced to swat while your partner may not. Scientists don't really know what to make of that insect favoritism, although they cite such things as wearing bright clothing, using perfumes and soaps and the carbon dioxide we release through our skin as attractants.

"If you have 190 people in an outdoor area, at least one is highly attractive (to mosquitoes) and one is highly repellent," said Jerry Butler, a professor emeritus and entomologist with the University of Florida's Institute of Food and Agricultural Sciences.

"We believe the depositing of cholesterol on the skin is an attractant along with the carbon dioxide. And of course if you're the only one out there, they'll choose the one person available," he said.

Then there are the ticks, particularly the blacklegged or "deer ticks" that can do great and lasting harm as carriers of Lyme disease. That is a flu-like illness appearing initially as a red "bulls-eye rash." It can strengthen to become a life-threatening disorder of the lungs, heart and nervous system.

More than 21,000 cases of Lyme disease are reported every year, making it the most common illness transmitted by insects or animals in the U.S., the CDC said.

"You're a lot less likely to get a bad bite from a mosquito than you are a tick," said Charles Cantrell, a research chemist with the USDA's Agriculture Research Service in Oxford, Miss. Cantrell was a member of the scientific team that successfully extracted a natural insect repellent from the American and Japanese Beautyberry bushes.

"We followed the trail of a traditional folk remedy by purifying some specific compounds from the (Beauty) berries," Cantrell said. "We found it very effective against two different kinds of mosquitoes (Culex and Aedes). It was equally effective against ticks. There's a lot of good evidence building in support of this compound."

As there is for Geraniol, a botanical repellent derived from lemon grass and several other natural ingredients discovered by the University of Florida's Butler. BugBand Inc., one of the companies licensed to sell Geraniol-based products, has sent hundreds of its strongly scented plastic bracelets to ground troops in the Persian Gulf, where they've been reported effective against sand fleas, among other things.

Along with the repellents, you always can add some "mosquito plants" to your yard. A little catnip planted along walkways, some geranium flowering in window boxes and the aforementioned Beautyberry bushes have been said to keep insects at a distance.

Landscaping to discourage ticks and their hosts also may provide some crossover benefits in ridding yourself of West-Nile-carrying mosquitoes, said Patrick Guilfoile, head of the Biology Department at Bemidji (Minn.) State University and author of "Ticks Off! Controlling Ticks That Transmit Lyme Disease on Your Property."

"Mosquitoes have a much larger range," he said. "And there, you're generally dealing with standing water. Ticks, on the other hand, draw their moisture from the humidity in the air."

Remove some of the habitat and you remove some of the threat, Guilfoile said.

"Studies show 70 to 75 percent of all people with Lyme disease get it in their own yards."

For more about the dangers posed by biting insects, see this Centers for Disease Control and Prevention Web site:

http://www.cdc.gov/ncidod/dvbid/westnile/index.htm.