As if mosquitoes are not pesky enough, they also can carry disease. So, when you swat, feel righteous that you have not only destroyed an annoying critter, but in the process you have reduced---by at least one--the number of mosquitoes who can carry West Nile Virus (WNV).

WNV has existed in the West Nile area as well as other areas of the globe for many years. However, five years ago it made its first appearance in the U.S. when it showed up in New York City. It continues to spread across the U.S., all the way to the west coast, and is now a permanent resident throughout the U.S. Several thousand cases of human WNV disease occur annually, and spread of the disease can be expected to continue.

Transmission

The transmission cycle of WNV is important. Mosquitoes become infected with WNV when they feed on birds, particularly blue jays and crows, which carry the virus. Once the virus has been acquired by the marauding mosquito, it is injected into the next victim, and that could be you or one of the children in your care. West Nile Virus cannot be transmitted from person-to-person

Symptoms and Treatments

West Nile Virus usually causes no symptoms in humans; at most, there may be a mild fever lasting a few days, followed by no lasting problems. These mild symptoms are known as West Nile fever.

However, in a few people, the virus may cause headache, rash, swollen lymph nodes, and “pinkeye” in addition to the fever. Although uncommon, these mild symptoms can worsen, with signs of disorientation, muscle weakness, severe headache, and high fever. Comas may occur, and even, rarely, death. These symptoms are signs that the virus has invaded the nervous system. This is West Nile encephalitis. Less than 1 percent of people infected with WNV become seriously ill, and only a very few of these people actually die from the illness.

There is no antibiotic treatment for West Nile Virus because antibiotics work only for bacterial infections and have no effect on viral illness. When someone does become very ill, supportive care should be given: nourishment, intravenous fluids to prevent dehydration, and surveillance to watch for signs of secondary infection.

Avoiding Mosquitoes

Not all mosquitoes are infected with West Nile Virus. A clue to the presence of the disease in mosquitoes is finding unusual numbers of dead birds in the area, particularly crows and jays, although more than 100 types of birds have been found to have the disease. Anyone who finds a dead bird should notify their local health department. Although there is no evidence that a person can get WNV from handling infected birds, dead or alive, it is wise not to handle the bird. Most birds, like most humans, are not killed by WNV.

The only sure way to prevent West Nile Virus infection is to prevent bites by infected mosquitoes. Here are some suggestions for caregivers:

• Children and providers should consider staying indoors during high-risk periods for mosquito bites--dawn, dusk, and evening.
• When going outside, children and providers should wear protective clothing as much as possible, including long sleeves and pants. However, be aware that such clothing does not offer total protection. Bites can still occur through thin fabric. If fabric is thin, it can be sprayed with insect repellent. It is not necessary to spray the skin under the fabric.
• Insect repellent containing a chemical known as DEET should be used on skin or thin fabric when children and providers go outside. Mosquitoes are effectively repelled by DEET, which is an ingredient in almost all insect repellents; look for it on the label.
• Do not use DEET on children less than two months old. Instead, place mosquito netting over infant carriers when you are outside with infants.

Insect Repellents

Not all repellents have the same concentrations of DEET. Higher concentrations of DEET are not more effective than lower ones, but their protection lasts longer. A product containing 10 percent DEET is appropriate for children, and protection lasts two-three hours. Apply DEET repellent sparingly to exposed skin, carefully following directions on the label.

Do not spray around the face. Instead, spray some on your hands and rub it on the face, avoiding the eye area. Do not put the repellent on children’s hands because they could rub their eyes and cause discomfort. After returning indoors, it is good to sponge off the sprayed areas of skin to reduce the chance of skin irritation.

The Centers for Disease Control and Prevention (CDC) does not recommend use of products that combine sun screen and DEET because the instructions for safe use of sun screen and safe use of DEET are different. Also, in most situations, DEET does not need to be reapplied as often as sun screen.

There are other repellent preparations on the market in addition to DEET, but none are as effective as DEET. Burning citronella candles is ineffective in warding off mosquitoes, and it can present a fire or burn hazard as well. It was once thought that Vitamin B1 would make a person’s perspiration mosquito-repellent, but this is not true. Cosmetic preparations that do not contain DEET offer some protection, but may only be effective for short periods of time.

Reducing the Mosquito Population

One of the most effective preventive measures against West Nile Virus is to reduce the mosquito population. Mosquitoes breed in standing water, so follow these suggestions:

• Drain all standing water in outside areas, if possible.
• If standing water cannot be drained, it may be necessary to use larvicides (pesticides) in the water. These products should be applied by a certified, licensed pesticide applicator. Pesticide label instructions should always be carefully followed, and pesticides should never be applied when children are present.
• Empty and rinse birdbaths and water play areas at least weekly.
• Check your property (and ask your neighbors to check theirs) for water standing in flower pots, buckets, or other containers. Old tires, including tire swings, often hold water and provide perfect breeding spots for mosquitoes.
• Be sure rain gutters are not clogged.

Eradication of mosquitoes by spraying whole communities can be helpful, though far from reassuring. Spraying is usually only effective over very small areas. Consider the location of your childcare program to see whether there are likely mosquito breeding sites nearby that could increase the threat of West Nile Virus for your children and staff. Talk to your neighbors about how to reduce WNV risk, or work with the local health department to encourage all local business and home owners to take action.

Don Palmer, MD
Alabama Chapter, American Academy of Pediatrics

INTERNET RESOURCES

The Centers for Disease Control and Prevention offers answers to commonly-asked questions about WNV, how to avoid mosquito bites, and how to “mosquito proof.” Also on this site are questions and answers about using DEET. www.cdc.gov/ncidod/dvbid/westnile/

Questions and answers on West Nile Virus and children in childcare from the New York City Department of Health and Mental Health, ww.ci.nyc.ny.us/html/doh/html/wnv/wnvfaq15.html

RESOURCES

The National Pesticide Information Center has fact sheets on pesticide topics and specific ingredients in pesticides, including DEET, 800-858-7378, npic.orst.edu/