Outbreaks of West Nile virus disease occur each summer in the United States says the CDC, but this year, some areas of the country are experiencing earlier and greater activity.
So far in 2012, 42 states and 241 cases of WNV have been reported in people, birds and mosquitoes, making this the highest number of cases reported through the end of July since 2004. The virus has killed four people already this year even though infections don't usually peak until mid-August.
Almost 80 percent of the cases have been reported from three states, Texas, Mississippi, and Oklahoma said the CDC. With no medications to treat, or vaccines to prevent West Nile virus infection, the center is urging people to take preventative measures against the virus.
WNV is a seasonal virus, transmitted to people through the bite of infected mosquitoes. Most people are infected between the months of June to September, but the virus peaks around mid-August. The number of infection cases is often to tied to increased mosquito activity, and 2012 is proving to be an extra busy year.
"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, but factors such as weather and mosquito numbers can help to spread the virus, as can human behavior. Still, "regardless of the reasons for the increase," Fischer adds, "people should be aware of the West Nile virus activity in their area and take action to protect themselves and their family."
Those protection measures include the use of insect repellents and covering up when mosquito activity is at its highest, typically dawn and dusk. Preventative measures can also help. Installing screens on windows and doors plus emptying any vessel that can hold standing water outside the home, will prevent mosquitoes from breeding.
The CDC says that the chance that any one person is going to become ill from a single mosquito bite remains low, but the risk of severe illness and death is highest for people over 50 years old. People of all ages can become sick though and around 1 in 5 people who are infected will develop symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or rash.
In rare cases (less than 1 percent), a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues) can occur and around 10 percent of people who develop neurologic infection due to West Nile virus will die. People with compromised immune systems or certain health conditions such cancer, diabetes, hypertension, kidney disease, and organ transplants, are at greater risk for serious illness.
For further information on West Nile Virus activity in your area and prevention tips, visit Cdc.gov/westnile