Symptoms & Treatment

Symptoms

No symptoms in most people. Most people (70-80%) who become infected with West Nile virus do not develop any symptoms.
Febrile illness in some people. About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea, or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months.
Severe symptoms in a few people. Less than 1% of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis (inflammation of the brain or surrounding tissues).

• The symptoms of neurologic illness can include headache, high fever, neck stiffness, disorientation, coma, tremors, seizures, or paralysis.
• People with certain medical conditions, such as cancer, diabetes, hypertension and kidney disease are also at greater risk for serious illness.
• Recovery from severe disease may take several weeks or months. Some of the neurologic effects may be permanent.
• About 10 percent of people who develop neurologic infection due to West Nile virus will die.

Treatment

• No vaccine or specific antiviral treatments for West Nile virus infection are available.
• Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms
• In severe cases, patients often need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication, and nursing care.

Transmission
 West Nile virus is most commonly transmitted to humans by mosquitoes.
Additional routes of human infection have also been documented. It is important to note that these methods of transmission represent a very small proportion of cases:

• Blood transfusions
• Organ transplants
• Exposure in a laboratory setting
• From mother to baby during pregnancy, delivery, or breastfeeding 

West Nile virus is not transmitted:

• From person-to-person or from animal-to-person through casual contact. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.
• From handling live or dead infected birds. You should avoid bare-handed contact when handling any dead animal. If you are disposing of a dead bird, use gloves or double plastic bags to place the carcass in a garbage can.
• Through consuming infected birds or animals. In keeping with overall public health practice, and due to the risk of known food-borne pathogens, always follow procedures for fully cooking meat from either birds or mammals.

Prevention & Control

The most effective way to avoid West Nile virus disease is to prevent mosquito bites. Be aware of the West Nile virus activity in your area and take action to protect yourself and your family.

Avoid Mosquito Bites

• Use insect repellents when you go outdoors. Repellents containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products provide longer-lasting protection. To optimize safety and effectiveness, repellents should be used according to the label instructions.
• 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.
• Take extra care during peak mosquito biting hours. Take extra care to use repellent and protective clothing from dusk to dawn or consider avoiding outdoor activities during these times.

Mosquito-Proof Your Home

• Install or repair screens on windows and doors to keep mosquitoes outside. Use your air conditioning, if you have it.
• Help reduce the number of mosquitoes around your home by emptying standing water from flowerpots, gutters, buckets, pool covers, pet water dishes, discarded tires, and birdbaths on a regular basis.

Help Your Community West Nile Virus Surveillance and Control Programs

• Support your local community mosquito control programs. Mosquito control activities are most often handled at the local level, such as through county or city government. The type of mosquito control methods used by a program depends on the time of year, the type of mosquitoes to be controlled, and the habitat structure. Methods can include elimination of mosquito larval habitats, application of insecticides to kill mosquito larvae, or spraying insecticides from trucks or aircraft to kill adult mosquitoes. Your local mosquito control program can provide information about the type of products being used in your area. Check with your local health department for more information. Contact information may be found in the blue (government) pages of the phone book.