West Nile Virus
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West Nile virus (WNV) is one of a family of viruses that can be transmitted by the bite of an infected mosquito. The mosquitoes become infected with WNV by feeding on birds that have the virus in their bloodstream. Very few mosquitoes are infected with WNV.
If an infected mosquito bites me, how long until symptoms develop?
Most people bitten by infected mosquitoes do not develop any symptoms. However, when symptoms of infection do occur, they usually appear 3 to 14 days after they are bitten by the infected mosquito.
How is WNV transmitted?
• Most often WNV is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds.
• In a very small number of cases, WNV also has spread through blood transfusions, organ transplants, breast feeding, and even during pregnancy from mother to baby.
WNV is not spread through casual contact such as touching or kissing a person with the virus.
If I live in an area with birds and mosquitoes with WNV, can I get it?
It is highly unlikely.
Less than 1% of mosquitoes are infected with the virus.
• Only about 1 in 5 people who are bitten by an infected mosquito experience illness.
• Chances of severe illness are extremely small.
What are the symptoms?
Most people (about 4 out of 5) who are infected with WNV will not show any symptoms at all. Some persons experience mild symptoms. This happens to about 1 out of 5 persons. These symptoms include:
• Fever ,
• Headache / body aches / fatigue,
• Nausea or vomiting, and
• Sometimes swollen lymph glands or a skin rash on the chest, stomach or back.
Symptoms can last for as short as a few days or in some cases for several weeks.
About 1 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 last forever.
Who is most at risk for WNV?
All residents of areas where virus activity has been identified are at risk of getting West Nile virus although people over 50 years of age should be careful as they have a higher risk of developing serious symptoms of WNV if they do get sick.
Does WNV treatment require hospitalization and can it be fatal?
• About 1 in 150 people infected with WNV will develop serious illness and may require hospitalization.
• Supportive therapy, such as IV fluids, pain medication, and anti-inflammatory medication, may be used to help with symptoms.
• 3—15% of those who develop severe illness may die, particularly if they are elderly.
• There is no human vaccine or treatment.
• Duration of mild illness may last 2—10 days and severe illness may last several weeks or be permanent.
What is the case count?
To view current case counts and historical WNV data please visit the following website:
http://www.cdc.gov/ncidod/dvbid/westnile/index.htm
Is there a way to prevent the spread of West Nile virus?
• Stay indoors at dawn, dusk, and in the early evening.
• Wear long-sleeved shirts and long pants when outdoors.
• Avoid shaded areas where mosquitoes may be resting.
• Use insect repellent containing 20-30% DEET for individuals 2 months and older. For babies under 2 months use mosquito netting over baby carrier. Using more DEET than necessary will not improve protection but may cause adverse reactions.
• Get rid of mosquito breeding sites by emptying standing water from birdbaths, boats, buckets, tires, unused pool, pool covers, roof gutters, and other containers. Change the water in pet dishes and replace the water in birdbaths weekly. Keep children’s wading pools empty and on their sides when they are not being used.
• Make sure you have good screens on your windows and doors to keep mosquitoes out.
• Report mosquito concerns to your local mosquito control agency: 918-595-4219
For more information on West Nile Virus, visit:
Tulsa Health Department
(918) 595-4505
epidemiology@tulsa-health.org
Oklahoma State Department of Health
(405) 271-4060
www.health.state.ok.us/program/cdd/infec.html
Centers for Disease Control and Prevention
(888) 443-7232
www.cdc.gov
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