HEALTH

West Nile Virus Season Starts Early, CDC Warns

HEMET, CA - APRIL 26:  A field sample of mosquitoes that could carry West Nile Virus is seen at offices of the Riverside County Department of Environmental Health on April 26, 2007 in Hemet, California. California health officials announced this week that West Nile Virus season is starting earlier than usual because of an unusually warm March. Mosquitoes that carry the virus have begun breeding earlier than usual and the West Nile Virus has been detected in mosquito pools, birds, or horses in eight California counties. Although the virus has not been detected in humans so far this year, 24 people have died and 1,200 sickened by the virus over the past two years in California. West Nile can be transmitted from infected birds, squirrels, and other animals to humans and animals such as horses through several varieties of female mosquitoes. The disease first appeared in the United States in 1999 in New York and killed hundreds of people during its westward expansion before gaining a firm foothold in California in 2004. In reaction to the early start of West Nile Virus season, the California State Legislature this week declared April 23-29 "West Nile Virus and Mosquito and Vector Control Awareness Week". The effected counties include Imperial, Los Angeles, Orange, Riverside, Santa Clara, San Diego, Sonoma and Stanislaus.  (Photo by David McNew/Getty Images)

HEMET, CA - APRIL 26: A field sample of mosquitoes that could carry West Nile Virus is seen at offices of the Riverside County Department of Environmental Health on April 26, 2007 in Hemet, California. California health officials announced this week that West Nile Virus season is starting earlier than usual because of an unusually warm March. Mosquitoes that carry the virus have begun breeding earlier than usual and the West Nile Virus has been detected in mosquito pools, birds, or horses in eight California counties. Although the virus has not been detected in humans so far this year, 24 people have died and 1,200 sickened by the virus over the past two years in California. West Nile can be transmitted from infected birds, squirrels, and other animals to humans and animals such as horses through several varieties of female mosquitoes. The disease first appeared in the United States in 1999 in New York and killed hundreds of people during its westward expansion before gaining a firm foothold in California in 2004. In reaction to the early start of West Nile Virus season, the California State Legislature this week declared April 23-29 "West Nile Virus and Mosquito and Vector Control Awareness Week". The effected counties include Imperial, Los Angeles, Orange, Riverside, Santa Clara, San Diego, Sonoma and Stanislaus. (Photo by David McNew/Getty Images)  (2007 Getty Images)

More cases of sickness related to the West Nile virus have been reported this year than any other time since 2004, health officials said Wednesday.

Through the end of July, 241 human cases have been reported in 22 states, including four deaths. Texas, especially around the Dallas area, has seen the bulk of them.

Health officials believe the mild winter, early spring and very hot summer have fostered breeding of the mosquitoes that spread the virus to people.

Most West Nile infections are reported in August and September, so it's not clear how bad this year will be. But it doesn't look good.

"Unless the weather changes dramatically, we'll see more cases (in 2012) than we have in the last couple of years," said Roger Nasci of the Centers for Disease Control and Prevention. He is chief of the CDC branch that tracks insect-borne diseases.

Mosquitoes pick up the virus from birds they bite and then spread it to people.

Only about one in five infected people get sick. One in 150 infected people will develop severe symptoms including neck stiffness, disorientation, coma and paralysis.

Of the 241 cases reported so far this year, 144 were severe cases in which the virus spread to the brain and nervous system and caused encephalitis or other problems. The last time so many serious cases were reported this early was 2004, when the number was 154.

West Nile virus was first reported in the United States in 1999 in New York, and then gradually spread across the country. Its peak occurred in 2002 and 2003, when severe illnesses numbered nearly 3,000 and deaths surpassed 260.

Last year was a mild one, with fewer than 700 human cases reported.

In recent years, the general pattern has been cases scattered across the country along with hot spots with more illnesses. The recurring hot spots include southeast Louisiana, central and southern California, and areas around Dallas, Houston, Chicago and Phoenix.

Those areas seem to have a combination of factors that include the right kinds of virus-carrying mosquitoes and birds, along with large numbers of people who can be infected, Nasci said.

The best way to prevent West Nile disease is to avoid mosquito bites. Insect repellants, screens on doors and windows and wearing long sleeves and pants are some of the recommended strategies. Also, empty standing water from buckets, kiddie pools and other places to discourage mosquito breeding.

Based on reporting by the Associated Press.

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