What is West Nile Virus?
West Nile Virus (WNV) is a mosquito-borne virus that was first detected in the United States in 1999. It is not known how the WNV was introduced into the United States but it may have entered in an infected traveler, bird, or mosquito. WNV has been present in Africa, West and Central Asia, and the Middle East for a long time. The majority of people and animals that are infected with WNV have no symptoms or only a mild illness. In rare cases, WNV can cause more serious conditions such as encephalitis (an inflammation of the brain) and/or meningitis (an inflammation of the linings of the brain and spinal cord).
How do mosquitoes become infected with West Nile Virus?
Mosquitoes become infected with WNV when they feed on birds that are infected with WNV. After a few days, infected mosquitoes can then transmit WNV to other birds, humans and horses. Only certain species of mosquitoes carry the virus and usually only a small percentage of mosquitoes are actually infective.
How do people become infected with West Nile Virus?
- 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.
What is "encephalitis"?
Encephalitis is an inflammation of the brain. In rare cases, WNV can cause encephalitis.
Signs and symptoms might include high fever, headache, confusion, disorientation, seizures, muscle weakness, and coma.
Who is at risk of getting sick from West Nile Virus?
- 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.
What are the symptoms of West Nile Virus infection?
- 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.
Is there a treatment for West Nile Virus infection?
There is no specific treatment for WNV infection. As with other viral illnesses, supportive care and symptomatic therapy are given.
Is there a vaccine to prevent West Nile Virus infection?
There is no vaccine currently available to protect people against West Nile virus infection. However, research is underway to develop a vaccine for people. There is a vaccine available for horses.
If bitten by a mosquito, should I be tested for WNV?
No. Even in areas where mosquitoes and birds are known to carry WNV, only a small percentage of mosquitoes are infected. The majority of people will not experience any symptoms if an infected mosquito bites them. Small percentages of people develop mild symptoms and recover without specific medication or laboratory testing. Those over age 50 are more likely to develop severe symptoms requiring medical care. Contact your health care provider if you are concerned about WNV infection.
What time of year are mosquito-borne viruses spread?
In Arizona, mosquito-borne viruses are most likely to be spread from May through October during the peak of mosquito activity.
How can I help protect myself and my family from West Nile Virus?
The best way to protect you and your family from WNV, or any other mosquito-borne illness, is to reduce the number of mosquitoes around your home and neighborhood and to take personal precautions to avoid mosquito bites. These are some of the preventative steps that you can easily take:
- Eliminate standing water where mosquitoes can breed. Check for items outside the home that collect rain or sprinkler water, such as cans, bottles, jars, buckets, old tires, drums and other containers.
- Change water in flower vases, birdbaths, planters and animal watering pans at least twice a week.
- Repair leaky pipes and outside faucets, and move air conditioner drain hoses frequently.
Avoid being bitten by mosquitoes when going outside at night by using insect repellent. Wear lightweight clothing that covers the arms and legs.
- The easiest and best way to avoid WNV is to prevent mosquito bites. When you are outdoors, use insect repellent containing an EPA-registered active ingredient. Follow the directions on the package. 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.
Which animals can get infected with West Nile Virus?
WNV infection has been reported in more than 150 bird species. Certain types of birds such as crows, ravens and jays appear to be most susceptible to WNV infection. Horses are also susceptible to WNV infection but a vaccine is available through veterinarians. WNV infections affecting the nervous system have also been reported in squirrels, goats and sheep, but the susceptibility of these animals to WNV is not well known. WNV illness in dogs and cats is rare. Contact your veterinarian for information about pets and livestock.
What should I do if I find a dead bird?
If you find a dead bird, you should contact your county environmental health department for more information. A program has been established to test dead birds reported in Arizona. However, not all dead birds can be tested for WNV. To be tested, the dead bird should be relatively fresh, not scavenged or decomposed, and with little or no odor. Also, testing is not being offered for baby birds or pigeons. Always wear gloves when handling dead birds. Refrigerate the dead bird until it is submitted for testing (but Do Not Freeze it!).
Can a person get West Nile Virus infection by eating infected birds?
Proper cooking kills WNV. Consequently, there is no danger associated with eating birds that have been properly cooked. Hunters are encouraged to wear gloves whenever field dressing game, including birds.
What is Arizona doing to prepare for West Nile Virus?
County and state health workers monitor and test mosquitoes at selected sites, dead birds and sentinel chicken flocks (17) for mosquito-borne viruses. Mosquito surveillance involves trapping mosquitoes, counting them, identifying the species involved, and testing the appropriate species for viruses. These surveillance methods are used to better identify areas where mosquito control efforts are needed. Detection and control of mosquito breeding sites depends upon integrated efforts among state, county, and tribal agencies as well as private citizens.
Where can I get more information on West Nile Virus?
Call Yuma County Public Health Services at the number below for additional information. Visit the Centers for Disease Control and Prevention's West Nile Virus Information. You can also visit the Arizona Department of Health Service's West Nile Virus Information.
Yuma County Public Health Services District
Environmental Health Division
Phone (928) 317-4584
Fax (928) 317-4583