This last week the CDC has some rather startling numbers to report about the encroachment of West Nile Virus (WNV) into our daily lives. So far in 2012, 47 states have reported West Nile virus infections in people, birds, or mosquitoes with a total of 1118 cases of West Nile virus disease in people, including 41 deaths. Of these, 629 (56%) were classified as neuroinvasive disease (such as meningitis or encephalitis) and 489 (44%) were classified as non-neuroinvasive disease. There are three definitions that you need to become familiar with to understand the disease:
- Neuroinvasive disease cases, refers to severe cases of disease that affect a person’s nervous system. These include encephalitis which is an inflammation of the brain, meningitis which is an inflammation of the membrane around the brain and the spinal cord and acute flaccid paralysis which is an inflammation of the spinal cord that can cause a sudden onset of weakness in the limbs and/or breathing muscles.
- Nonneuroinvasive disease cases refers to typically less severe cases that show no evidence of neuroinvasion—primarily West Nile fever. WN fever is considered a notifiable disease, however the number of cases reported (as with all diseases) may be limited by whether persons affected seek care, whether laboratory diagnosis is ordered and the extent to which cases are reported to health authorities by the diagnosing physician.
- Presumptive viremic blood donors (PVDs) are people who had no symptoms at the time of donating blood (people with symptoms are deferred from donating) through a blood collection agency, but whose blood tested positive in preliminary tests when screened for the presence of West Nile virus. Some PVDs do go on to develop symptoms after donation, at which point they would be included in the count of human disease cases by their state.
The 1118 cases reported in 2012 is the highest number of West Nile virus disease cases reported to CDC through the third week in August since West Nile virus was first detected in the United States in 1999. Approximately 75 percent of the cases have been reported from 5 states (Texas, Mississippi, Louisiana, South Dakota, and Oklahoma) and almost half of all cases have been reported from Texas (537 cases and 19 deaths).
So…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? 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.
- 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? It primarily spread by mosquito bites.
- 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.
Be smart – when outside think about mosquito protection regardless of which state you live in!
Number of infections by State; http://www.cdc.gov/ncidod/dvbid/westnile/surv&controlCaseCount12_detailed.htm