Much like the uninvited houseguest who unpacks and never leaves, West Nile virus has come to Texas to stay. “West Nile virus first appeared in Texas in June 2002 and has since moved across the state,” said Joe Garrett, a veterinarian with the zoonosis control division at the Texas Department of Health (TDH). “We probably should consider West Nile virus endemic to the state now, much like St. Louis encephalitis is permanently established in Texas,” Garrett said. “But West Nile virus is new to us, and we still are trying to understand it. We cannot predict what kind of a season we will have this year.” In 2002, West Nile virus was reported in 213 Texas counties. A total of 202 serious West Nile cases, including 13 deaths, were reported in humans. The virus also was identified in 1,697 horses and 518 birds. The TDH Laboratory tested more than 160,000 mosquitoes in 7,350 groups or pools last year for a variety of mosquito-borne infections including West Nile virus; St. Louis encephalitis; and Western, Eastern and Venezuelan equine encephalitis. Of these mosquito pools, 466 of them were positive for a variety of mosquito-borne viruses and 189 pools were positive for West Nile virus. Mosquitoes generally are collected and tested from May through November, but several areas in the state have year-round surveillance. “Testing mosquitoes and dead birds’generally jays, crows and hawks’gives us a way of actively tracking the virus to alert affected communities that they may need to take precautions to protect themselves, ” Garrett said. “Tracking illnesses in humans and horses also gives us a more complete picture of the spread of the virus.” Mosquitoes get the West Nile virus by biting infected birds. People and animals get West Nile from the bite of an infected mosquito, not from other people, animals or birds. West Nile virus infections usually are mild with flu-like symptoms including fever, headache, sore throat, body aches and fatigue, occasionally with skin rash and swollen lymph glands. Symptoms of more severe West Nile infections’encephalitis and meningitis’include headache, high fever, stiff neck, disorientation, tremors, convulsions, muscle weakness, coma and paralysis. If you have these symptoms, contact your health care provider right away. The incubation period for West Nile virus is three to 14 days. Mild symptoms may last a few days while symptoms of the more severe illness may last several weeks. Neurological effects may be permanent, and West Nile can be fatal. Fewer than 1 percent of those bitten by infected mosquitoes become severely ill. Currently no vaccine is available to combat West Nile virus in people, and no specific treatment is given for the infection other than supportive therapies for fever or pain. “People can, however, do a great deal to protect themselves, their families and their communities,” said Dr. Eduardo Sanchez, Texas Commissioner of Health. “Reducing exposure to mosquitoes is one of the most important things.” Sanchez urged people to remember the four Ds: ‘ Dusk to Dawn’Stay indoors from dusk to dawn, times when those mosquitoes likely to carry the infection are most active. ‘ Dress’Dress in pants and long sleeves when you are outside, especially in mosquito-infested areas. ‘ DEET (N,N-diethyl-m-toluamide)’Apply insect repellent that contains DEET. Read and follow label instructions. Spray both exposed skin and clothing with repellent. ‘ Drain’Get rid of standing water in your yard and neighborhood. Old tires, flowerpots, clogged rain gutters, leaky pipes and faucets, birdbaths and wading pools can be breeding sites for mosquitoes. Garrett said it also is important to keep mosquitoes out of the house. “Be sure door, porch and window screens are in good condition,” he said. Cities, counties, mosquito control districts or local health departments will implement pesticide application if they consider such action appropriate for their communities. “West Nile virus can infect just about any animal from alligators to zebras,” Garrett said, “but most do not become sick.” Horses, however, seem to be most susceptible to the infection, the veterinarian noted. “A vaccine that is about 95 percent effective in preventing West Nile in horses is available,” Garrett said. “Horses not previously immunized need two shots given three to six weeks apart, with a annual booster thereafter. Protection begins about three to four weeks after the last shot.” Even if horses were vaccinated late last year, Garrett advises that the animals be given the booster shot now rather than waiting a full year. West Nile virus was originally detected in Uganda in 1937. It was first identified in the United States in New York in 1999 and has since spread westward and southward across the country to 44 states and the District of Columbia. A total of 4,008 human cases were recorded nationwide by the end of last year. TDH operates a toll-free line in English and Spanish'(888) 883-9997’providing information on dead bird testing, mosquito surveillance and other West Nile virus topics. Additional information, statistics and maps are available by clicking on the West Nile virus information link on the TDH Web site at www.tdh.state.tx.us.