West Nile Virus
Here are the facts about West Nile.
The West Nile virus produces one of three different outcomes in humans. The first is an asymptomatic infection; the second is a mild febrile syndrome termed West Nile fever; the third is a neuroinvasive disease termed West Nile meningitis or encephalitis. The population proportion of these three states is roughly 110:30:1.The second, febrile stage has an incubation period of two to eight days followed by fever, headache, chills, diaphoresis (excessive sweating), weakness, lymphadenopathy (swollen lymph nodes), drowsiness, pain in the joints and symptoms like those of influenza. Occasionally, some patients experience a short-lived truncal rash or gastrointestinal symptoms, including nausea, vomiting, loss of appetite, or diarrhea. Symptoms are generally resolved within seven to 10 days, although fatigue can persist for some weeks and lymphadenopathy up to two months.The more dangerous encephalitis is characterized by similar early symptoms, but also a decreased level of consciousness, sometimes approaching near-coma. Deep tendon reflexes are hyperactive at first, later diminished. There are also extrapyramidal disorders. Recovery is marked by a long convalescence with fatigue.More recent outbreaks have resulted in a deeper study of the disease and other, rarer, outcomes have been identified. The spinal cord may be infected, marked by anterior myelitis with or without encephalitis. WNV-associated Guillain-Barré syndrome has been identified and other rare effects include multifocal chorioretinitis (which has 100% specificity for identifying WNV infection in patients with possible WNV encephalitis)
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. 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.
For detailed information about using repellents, see the Insect Repellent Use and Safety questions.
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.
Kids can learn how to protect themselves from mosquito bites on “The Buzz-z-z-z on West Nile Virus” (on BAM!, the CDC site for kids).