Washington, D.C. – As of September 11th, 2012, 48 states have reported West Nile virus infections in people, birds, or mosquitoes. A total of 2,636 cases of West Nile virus disease in people, including 118 deaths, have been reported to CDC.
Of these, 1,405 (53%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 1,231 (47%) were classified as non-neuroinvasive disease.
West Nile virus (WNV) activity reported to ArboNET, by state, United States, 2012 (as of September 11th, 2012)
The 2,636 cases reported thus far in 2012 is the highest number of West Nile virus disease cases reported to CDC through the second week in September since 2003. Two thirds of the cases have been reported from six states (Texas, Louisiana, South Dakota, Mississippi, Michigan, and Oklahoma) and 40 percent of all cases have been reported from Texas.
Since 1999, more than 30,000 people in the United States have been reported as getting sick with West Nile virus. Infected mosquitoes spread West Nile virus (WNV) that can cause serious, life altering disease.
There have been 10 cases of West Nile Virus in Tennessee in 2012.
What Is West Nile Virus?
West Nile virus (WNV) is a potentially serious illness. Experts believe WNV is established as a seasonal epidemic in North America that flares up in the summer and continues into the fall.
What Can I Do to Prevent WNV?
New! Prevention measures consist of community-based mosquito control programs that are able to reduce vector populations, personal protection measures to reduce the likelihood of being bitten by infected mosquitoes, and the underlying surveillance programs that characterize spatial/temporal patterns in risk that allow health and vector control agencies to target their interventions and resources.
The easiest and best way to avoid WNV is to prevent mosquito bites.
Many mosquitoes are most active at dusk and dawn. Be sure to use insect repellent and wear long sleeves and pants at these times or consider staying indoors during these hours.
Make sure you have good screens on your windows and doors to keep mosquitoes out.
Get rid of mosquito breeding sites by emptying standing water from flower pots, buckets and barrels. Change the water in pet dishes and replace the water in bird baths weekly. Drill holes in tire swings so water drains out. Keep children’s wading pools empty and on their sides when they aren’t being used.
What Are the Symptoms of WNV?
Serious Symptoms in a Few People. About one in 150 people infected with WNV will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
Milder Symptoms in Some People. Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks.
No Symptoms in Most People. Approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all.
How Does West Nile Virus Spread?
Infected Mosquitoes. Most often, WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread WNV to humans and other animals when they bite.
Transfusions, Transplants, and Mother-to-Child. In a very small number of cases, WNV also has been spread through blood transfusions, organ transplants, breastfeeding and even during pregnancy from mother to baby.
Not through touching. WNV is not spread through casual contact such as touching or kissing a person with the virus.
How Soon Do Infected People Get Sick?
People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito.
How Is WNV Infection Treated?
There is no specific treatment for WNV infection. In cases with milder symptoms, people experience symptoms such as fever and aches that pass on their own, although even healthy people have become sick for several weeks. In more severe cases, people usually need to go to the hospital where they can receive supportive treatment including intravenous fluids, help with breathing and nursing care.
What Should I Do if I Think I Have WNV?
Milder WNV illness improves on its own, and people do not necessarily need to seek medical attention for this infection though they may choose to do so. If you develop symptoms of severe WNV illness, such as unusually severe headaches or confusion, seek medical attention immediately. Severe WNV illness usually requires hospitalization. Pregnant women and nursing mothers are encouraged to talk to their doctor if they develop symptoms that could be WNV.
What Is the Risk of Getting Sick from WNV?
People over 50 at higher risk to get severe illness. People over the age of 50 are more likely to develop serious symptoms of WNV if they do get sick and should take special care to avoid mosquito bites.
Being outside means you’re at risk. The more time you’re outdoors, the more time you could be bitten by an infected mosquito. Pay attention to avoiding mosquito bites if you spend a lot of time outside, either working or playing.
Risk through medical procedures is very low. All donated blood is checked for WNV before being used. The risk of getting WNV through blood transfusions and organ transplants is very small, and should not prevent people who need surgery from having it. If you have concerns, talk to your doctor.
Pregnancy and nursing do not increase risk of becoming infected with WNV.
The risk that WNV may present to a fetus or an infant infected through breastmilk is still being evaluated. Talk with your care provider if you have concerns.
What Is the CDC Doing About WNV?
CDC is working with state and local health departments and other government agencies, as well as private industry, to prepare for and prevent new cases of WNV.
Some things CDC is doing include:
Manage and maintain ArboNET, a nation-wide electronic surveillance system where states share information about WNV and other arboviral diseases
Support states develop and carry out improved mosquito prevention and control programs
Developing better, faster tests to detect and diagnose WNV
Prepare updated prevention and surveillance information for the media, the public, and health professionals
Working with partners on the development of vaccines
What Else Should I Know?
If you find a dead bird: Don’t handle the body with your bare hands. Contact your local health department for instructions on reporting and disposing of the body. They may tell you to dispose of the bird after they log your report.
For more information Call 1.800.CDC.INFO (1.800.232.4636), Monday – Friday, 8:00am-8:00pm ET, Closed Holidays Email . (For TTY, call 1.888.232.6348.)
Questions & Answers
Q. What can I do to reduce my risk of becoming infected with West Nile virus?
A. Here are preventive measures that you and your family can take:
Protect yourself from mosquito bites:
Apply insect repellent to exposed skin. Generally, the the more active ingredient a repellent contains the longer it can protect you from mosquito bites. A higher percentage of active ingredient in a repellent does not mean that your protection is better—just that it will last longer. Click here for more on insect repellent active ingredients.Choose a repellent that provides protection for the amount of time that you will be outdoors.
Repellents may irritate the eyes and mouth, so avoid applying repellent to the hands of children.
Whenever you use an insecticide or insect repellent, be sure to read and follow the manufacturer’s DIRECTIONS FOR USE, as printed on the product.
Spray clothing with repellents containing permethrin or another EPA-registered repellent since mosquitoes may bite through thin clothing. Do not apply repellents containing permethrin directly to exposed skin. Do not apply repellent to skin under your clothing.
When weather permits, wear long-sleeved shirts and long pants whenever you are outdoors.
Place mosquito netting over infant carriers when you are outdoors with infants.
Consider staying indoors at dawn, dusk, and in the early evening, which are peak mosquito biting times.
Install or repair window and door screens so that mosquitoes cannot get indoors.
Help reduce the number of mosquitoes in areas outdoors where you work or play, by draining sources of standing water. In this way, you reduce the number of places mosquitoes can lay their eggs and breed.
At least once or twice a week, empty water from flower pots, pet food and water dishes, birdbaths, swimming pool covers, buckets, barrels, and cans.
Check for clogged rain gutters and clean them out.
Remove discarded tires, and other items that could collect water.
Be sure to check for containers or trash in places that may be hard to see, such as under bushes or under your home.
Note: Vitamin B and “ultrasonic” devices are NOT effective in preventing mosquito bites.
Q. What can be done to prevent outbreaks of West Nile virus?
A. Prevention and control of West Nile virus and other arboviral diseases is most effectively accomplished through integrated vector management programs. These programs should include surveillance for West Nile virus activity in mosquito vectors, birds, horses, other animals, and humans, and implementation of appropriate mosquito control measures to reduce mosquito populations when necessary. Additionally, when virus activity is detected in an area, residents should be alerted and advised to increase measures to reduce contact with mosquitoes. Details about effective prevention and control of West Nile virus can be found in CDC’s Guidelines for Surveillance, Prevention, and Control[PDF – 111 pages].
Q. Is there a vaccine against West Nile encephalitis?
A. No, but several groups are working towards developing a vaccine.
Q. Where can I get information about the use of pesticide sprays that are being used for mosquito control?
A. The federal agency responsible for pesticide evaluation is the Environmental Protection Agency (EPA). See the EPA Web site for detailed answers to the questions about pesticides used for mosquito control. Please, also check out our question and answer page on mosquito control recently updated.