West nile virus primary prevention

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Primary Prevention

For humans to escape infection the avoidance of mosquitos is key - remaining indoors(and not letting them indoors) at dawn and dusk, wearing light-colored clothing which protects arms and legs as well as trunk, using insect repellents on both skin and clothing (such as DEET, picaradin, or oil of lemon eucalyptus for skin and permethrin for clothes). Treatment is purely supportive: analgesia for the pain of neurologic diseases; rehydration for nausea, vomiting, or diarrhea; encephalitis may also require airway protection and seizure management.

On August 19, 2006, the LA Times reported that the expected incidence rate of West Nile was dropping as the local population becomes exposed to the virus. "In countries like Egypt and Uganda, where West Nile was first detected, people became fully immune to the virus by the time they reached adulthood, federal health officials said." [2] However days later the CDC said that West Nile cases could reach a 3-year high because hot temperatures had allowed a larger brood of mosquitoes. [3] Reported cases in the U.S. in 2005 exceeded those in 2004 and cases in 2006 exceeded 2005's totals.

When dealing with West Nile virus, prevention is your best bet. Fighting mosquito bites reduces your risk of getting this disease, along with others that mosquitoes can carry. Take the commonsense steps below to reduce your risk:

*Avoid bites and illness

Use Insect Repellent: On exposed skin when you go outdoors. Use an EPA-registered insect repellent such as those with DEET, picaridin or oil of lemon eucalyptus. Even a short time being outdoors can be long enough to get a mosquito bite.

Clothing Can Help Reduce Mosquito Bites: When weather permits, wear long-sleeves, long pants and socks when outdoors. Mosquitoes may bite through thin clothing, so spraying clothes with repellent containing permethrin or another EPA-registered repellent will give extra protection. Don't apply repellents containing permethrin directly to skin. Do not spray repellent on the skin under your clothing.

Be Aware of Peak Mosquito Hours The hours from dusk to dawn are peak biting times for many species of mosquitoes. Take extra care to use repellent and protective clothing during evening and early morning -- or consider avoiding outdoor activities during these times.

*Clean out the mosquitoes from the places where you work and play

Drain Standing Water: Mosquitoes lay their eggs in standing water.Limit the number of places around your home for mosquitoes to breed by getting rid of items that hold water.

Install or Repair Screens: Some mosquitoes like to come indoors. Keep them outside by having well-fitting screens on both windows and doors. Offer to help neighbors whose screens might be in bad shape.

*Help your community control the disease

Report Dead Birds to Local Authorities: Dead birds may be a sign that West Nile virus is circulating between birds and the mosquitoes in an area. Over 130 species of birds are known to have been infected with West Nile virus, though not all infected birds will die. It's important to remember that birds die from many other causes besides West Nile virus.

Mosquito Control Programs: Check with local health authorities to see if there is an organized mosquito control program in your area. If no program exists, work with your local government officials to establish a program. The American Mosquito Control Association can provide advice, and their book Organization for Mosquito Control is a useful reference.

Clean Up: Mosquito breeding sites can be anywhere. Neighborhood clean up days can be organized by civic or youth organizations to pick up containers from vacant lots and parks, and to encourage people to keep their yards free of standing water. Mosquitoes don't care about fences, so it's important to control breeding sites throughout the neighborhood.

Something to remember: The chance that any one person is going to become ill from a single mosquito bite remains low. The risk of severe illness and death is highest for people over 50 years old, although people of all ages can become ill.[4]

Possible vaccination

NIAID intramural scientists pioneered the concept of creating chimeric vaccines for flaviviruses in 1992. These scientists, now led by Dr. Brian Murphy, have developed a chimeric West Nile vaccine that uses a weakened dengue virus as a backbone to carry genes for the WNV protective antigens.

Led by Dr. Gary Nabel, researchers at the NIAID Vaccine Research Center (VRC), in collaboration with the San Diego, California-based biotechnology company Vical, Inc., have also developed investigational vaccines for preventing WNV infection. The vaccines are DNA-based.

In April 2005, following preclinical safety studies and viral challenge studies, the VRC initiated a Phase I clinical trial to evaluate safety, tolerability, and immune responses of a recombinant DNA vaccine in human volunteers. This trial represents the first demonstration in humans DNA vaccine to induce neutralizing antibody in a clinical trial.

Also in collaboration with Vical, Inc., the VRC developed a second-generation DNA vaccine using an improved vector expressing the same WNV proteins.

NIAID-supported researchers have developed hamster models of WNV infection (both immunocompetent and immunosuppressed hamsters) that closely mimic the human disease. Mouse models of WNV infection have also been developed. These animal models have proved useful in delineating progression of disease and are critical for evaluating the initial safety and efficacy of candidate vaccines, as well as the safety and efficacy of potential therapies. Using the hamster model, researchers were able to determine that prior infection with other related viruses may provide complete or partial immunity to WNV.

References

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