The West Nile Encephalitis Virus

West Nile Virus has now been reported in Southern California. Due to the danger to humans, birds, and horses, it is important to learn about this dangerous disease. I hope you find the following information valuable. The information comes from the CDC (www.cdc.gov) and the California West Nile Surveillance site (www.westnile.ca.gov). Please look at their sites for more in depth information. The Western Nile Encephalitis Virus was first seen in Uganda (Africa) in 1937. The first documented cases in the United States were in 1999. Since that time, it has spread to cover the East Coast, Midwest, and Southern United States.

How does the virus work? The virus requires the mosquito in order to propagate. The virus lives in the salivary glands and when the mosquito bites, it injects the virus into the host. Birds are the natural host, and the virus quickly replicates. When another mosquito bites the bird, it picks up the virus. The disease is deadly to birds, especially crows. Other animals can be infected, but luckily disease is rare. The only way to contract the disease is by being bitten by an infected mosquito.

Human and horse deaths have been reported? Should I worry? Less than 1% of people infected with the virus develop serious illness. With those with severe illness, fatalities are 3-15%, with the high rate among the elderly. The risk is very small. Symptoms of disease include: None (99%), fever, headache, nausea, mild skin rash, aches, and swollen lymph nodes. Rarely, encephalitis can occur, which can cause severe pain, lethargy, seizures, dementia, and death. There is no cure or vaccine at this point. If you exhibit these symptoms and have had mosquito exposure, please see your physician. There is a test to see if you are infected. Treatment is supportive. Remember that the disease is not spread person to person.
What about the horses? Horses are more affected than people are. The symptoms are similar to those caused by other encephalitis viruses. The rate of serious disease is 40% of infected horses. The WEE, EEE, and VEE vaccines do not cover Western Nile. The USDA has recently made a temporary approval for a vaccine by Fort Dodge. The effectiveness is still unknown. Horses with the infection are treated supportively.

What about dogs and cats? Viruses have been isolated from infected dogs and cats; however, there has been thus far, no symptoms in dogs, but some cats have died. The infection rate is fortunately very low, even in epidemic areas. If symptoms occur, supportive care is indicated.

What about pet birds? Over 111 species of birds have been found to contain the virus. Crows and Jays are most common, but all are at risk. Pet Birds, if kept indoors with good mosquito prevention, should be fine. What should you do if you see a dead bird? You should report it. Do not pick it up, just contact the California West Nile Surveillance at 877-WNV-BIRD or go to their website and click on Reporting a Dead Bird.

What is the government doing to stop the virus? The federal and state government are tracking the disease and performing diligent surveillance measures which have already been in place to monitor other encephalitis viruses. They are instituting stronger mosquito control measures and are educating the public as to prevention. Unfortunately, not much else can be done.

What can you do to prevent infection? Mosquito control is crucial. Make sure to have all screendoors well placed and without holes. Try to stay indoors at dusk and dawn, as mosquitoes are generally more active during these times. Keep raingutters clear and get rid of standing water. Stock ponds with mosquito-eating fish. If you go outside, wear long sleeved shirt and pants. Use a good-quality repellent with a high DEET concentration. DEET (N,N, diethyl-m-toluamide) is a good repellent. The higher the concentration, the longer it lasts. The CDC and EPA websites have great information on the repellents.

Overall, you should take adequate preventative measures. Mosquito prevention is good. I would recommend vaccinating horses for the disease by next year. Educate your friends and neighbors about the disease, so that they can start mosquito prevention as well. Report any suspicious or dead birds to the WNV Surveillance. Please look for updates on the CDC or WNV Surveillance web sites.