West Nile Virus

dont_bug_meWhat You Really Need To Know

What Is West Nile Virus?

West Nile virus (WNV) is a poten­tially seri­ous ill­ness. Experts believe WNV is now estab­lished as a sea­sonal epi­demic in North Amer­ica that flares up in the sum­mer and con­tin­ues into the fall. This fact sheet con­tains impor­tant infor­ma­tion that can help you rec­og­nize and pre­vent West Nile virus.

What Are the Symp­toms of WNV?

WNV affects the cen­tral ner­vous sys­tem. Symp­toms vary.

  • No Symp­toms in Most Peo­ple. Approx­i­mately 80 per­cent of peo­ple who are infected with WNV will not show any symp­toms at all.
  • Mild Symp­toms in Some Peo­ple. Up to 20 per­cent of the peo­ple who become infected will dis­play mild symp­toms, includ­ing fever, headache, and body aches, nau­sea, vom­it­ing, and some­times swollen lymph glands or a skin rash on the chest, stom­ach and back. Symp­toms typ­i­cally last a few days.
  • 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.
  • In very rare cases ani­mals and per­sons have died as a result of thie com­pli­ca­tions this ill­ness causes.

How Does It Spread?

  • Infected Mos­qui­toes. Gen­er­ally, WNV is spread by the bite of an infected mos­quito. Mos­qui­toes are WNV car­ri­ers that 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 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 mild symp­toms, peo­ple expe­ri­ence symp­toms such as fever and aches that pass on their own. 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?

Mild WNV ill­ness improves on its own, and peo­ple do not nec­es­sar­ily need to seek med­ical atten­tion for this infec­tion. 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 Catch­ing WNV?

For most, risk is low. Less than 1 per­cent of peo­ple who are bit­ten by mos­qui­toes develop any symp­toms of the dis­ease and rel­a­tively few mos­qui­toes actu­ally carry WNV.

Greater risk for those out­doors a lot. Peo­ple who spend a lot of time out­doors are more likely to be bit­ten by an infected mos­quito. They should take spe­cial care to avoid mos­quito bites.

Peo­ple over 50 can get sicker. 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.

Risk through med­ical pro­ce­dures is low. 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 before surgery.

Preg­nancy and nurs­ing do not increase risk of becom­ing infected with WNV.

What Can I Do to Pre­vent WNV?

The eas­i­est and best way to avoid WNV is to pre­vent mos­quito bites.

  • When you are out­doors, use insect repel­lents con­tain­ing DEET (N, N-diethyl-meta-toluamide). Fol­low the direc­tions on the pack­age. **Cau­tion**
  • Many mos­qui­toes are most active at dusk and dawn. Con­sider stay­ing indoors dur­ing these times or use insect repel­lent and wear long sleeves and pants. Light-colored cloth­ing can help you see mos­qui­toes that land on you.
  • 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 drainage 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 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.

For more infor­ma­tion, visit www.cdc.gov/westnile, or call the CDC pub­lic response hotline

at (888) 246‑2675 (Eng­lish), (888) 246‑2857 (Español), or (866) 874‑2646 (TTY)

This above infor­ma­tion is from the Depart­ment of Health and Human Ser­vices, Cen­ter for Dis­ease Con­trol and Pre­ven­tion dated June 9, 2003.

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