More than 240 cases of West Nile virus disease – including four deaths – have been reported this year – putting 2012 on track to be the worst year for the disease since 2004. Almost 80 percent of the cases have occurred in three states: Texas, Mississippi, and Oklahoma.

Those alarming numbers are prompting the Centers for Disease Control and Prevention (CDC) to urge urge people to take steps to prevent infections.

“It is not clear why we are seeing more activity than in recent years,” said Marc Fischer, M.D., M.P.H., medical epidemiologist with CDC’s Arboviral Diseases Branch.  “Regardless of the reasons for the increase, people should be aware of the West Nile virus activity in their area and take action to protect themselves and their family.” 

West Nile virus is transmitted to people by infected mosquitoes. In the United States, most people are infected from June through September, and the number of these infections usually peaks in mid-August. Seasonal outbreaks often occur in local areas that can vary from year to year. Many factors impact when and where outbreaks occur, such as weather, numbers of mosquitoes that spread the virus, and human behavior.

The best way to prevent West Nile virus disease is to avoid mosquito bites:

• Use insect repellents when you go outdoors. 
• Wear long sleeves and pants during dawn and dusk.
• Install or repair screens on windows and doors.  Use air conditioning, if you have it.
• Empty standing water from items outside your home such as flowerpots, buckets, and kiddie pools.

Approximately 1 in 5 people who are infected with West Nile virus will develop symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. Less than 1 percent will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues).  About 10 percent of people who develop neurologic infection due to West Nile virus will die. People over 50 years of age and those with certain medical conditions, such as cancer, diabetes, hypertension, kidney disease, and organ transplants, are at greater risk for serious illness.

There are no medications to treat, or vaccines to prevent, West Nile virus infection. People with milder illnesses typically recover on their own, although symptoms may last for several weeks.  In more severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care. Anyone who has symptoms that cause concern should contact a health care provider.

More information is available at www.cdc.gov/westnile