In up to 80 percent of victims, there are no symptoms. In up to 20 percent of victims, symptoms include:

• Fever
• Headache
• Nausea or vomiting
• Body aches

In a very small number of victims, they may experience severe symptoms including:

• High grade fever
• Stiff neck
• Stupor
• Becoming disoriented
• Tremors
• Convulsions
• Weakness in muscles
• Loss of vision
• Numbness
• Paralysis or Coma

high fever, sever headache, confusion,

West Nile Virus (WNV)

Overview/Prognosis:

In general, according to the US National Institutes of Health (NIH), the outcome in humans is usually excellent. Pregnant or nursing women should contact their doctors right away if any of the symptoms listed below are experienced. There is no preventive vaccine. Once you have had the virus, you are immune (possibly for life).

Locations of the virus:

To find out if there is known infection in your geographical area, check with the local area department of wildlife and naturalist resources, state epidemiologist at the state health department, or the US Geological Survey (USGS) National Wildlife Health Center, Madison, WI, 608-270-2400 for information on local area risk.

In Texas:

WNV is known to be widely around in Texas, the telephone number for Texas West Nile Virus information is 1-888-883-9997.

The stats for 2011 from the TX Dept of State Health Services Infectious Disease Control Unit: 54 cases in mosquitoes tested in 3 counties, 1 case in birds in 1 county, 2 cases in humans in 2 counties.

Incidence:

Less than 1% of bites from mosquitoes, even those known to be infected, result in severe human illness.

Severe Cases:

1 out of 150 people infected get severe illness and they are most likely to be over age 50.

These usually involve West Nile Encephalitis or WN Meningitis.

Symptoms in severe illness (one or more of):

High fever, Headache, Stiff Neck, Muscle Weakness, Disorientation, Stupor, Loss of Consciousness, Coma, Tremors, Convulsions, Numbness or paralysis of limb, Vision loss, Conjunctivitis, Cough, Dyspnea/shortness of breath.

50% of those infected have a rash (chest, stomach, back).

Symptoms may last several weeks.

Complications:

The worst complications are neurological, and may be permanent: Brain damage, Polio-like permanent weakness of muscles, Death (2005 stats= 3000 cases & 119 deaths. Approximately 10% of patients with brain inflammation do not survive.)

Treatment:

Seek urgent medical care if any of the severe symptoms above are experienced, and emergency care if there is a severe headache or confusion. Hospitalization is usually needed for IV fluids, other symptomatic treatment, respiratory care and nursing care.

Less Severe Cases (aka West Nile Fever):20% of people infected have milder symptoms.

Milder symptoms may include (one or more of):

Fever, Headache, Abdominal pain, Body aches, Nausea, Vomiting, Diarrhea, Swollen lymph glands, skin rash on chest, stomach and back, sore throat.

Symptoms last a few days to several weeks, but typically 3 - 6 days.

Treatment:

Call your attending physician if you have the milder symptoms listed above for instructions.

Other infections with WNV:

4 out of 5 people infected (80%) have no symptoms at all. Others report a few symptoms like those listed above, only milder.

Symptoms typically manifest within 3 - 14 days, if they are going to.

Diagnostics/Tests:

According to the CDC:

The most accurate way to diagnose this infection is with a serology test, which checks a blood or CSF sample for antibodies against the virus. More rapid techniques using polymerase chain reaction (PCR) may be used.

According to the TX Dept of State Health:

Laboratory confirmation of WNV is based on isolating virus from or demonstrating antigen or genomic sequence in tissue, blood, or CSF; demonstrating IgM antibody to WNV in CSF; demonstrating a 4-fold serial change in antibody titer to WNV in paired, acute, and convalescent serum samples obtained at least 2 weeks apart; or detecting both WNV-specific IgM and IgG antibody in a single serum specimen.

Risk Factors for infection and/or complications:

1. Age:

Those over 50 are at highest risk of experiencing severe cases and more severe symptoms.

50% of cases ending in death are in the very old; age > 77.

The very young are at higher risk, especially children under 10 and infants under 6 mo. due to immature immune system development.

2. Being outside:

Active people who are more likely to be outside and exposed to mosquitoes are at more risk.

3. Immunosuppression:

Those with immune system disorders, auto-immune disease, HIV/AIDS, organ transplants, receiving chemotherapy or other immune-suppressing drugs, infants and children under 10, and pregnant women are at very high risk of complications.

4. Pregnancy:

Pregnant women are at risk for more complicated illnesses, but not at a higher rate of infection compared to other otherwise healthy women.

Treatment:

There is no specific treatment, only supportive treatment of the symptoms.

Transmission: Migrating birds are the primary source of the virus, which is transmitted from them to humans and other animals by mosquitoes.

Mosquitoes get infected by feeding on an infected bird. The virus localizes in their salivary glands, so when they bite to feed on a host (human, bird, animal) the virus enters the host's body to start replication.

Eating the cooked meat of an infected animal is not believed to pass the virus.

Humans are known to be infected only through a bite from an infected mosquito, not from contact with other infected animals.

People can become infected through transfusions or organ transplants very rarely, and nursing or pregnant women with the virus have been known to occasionally infect the fetus or infant through the milk and in utero, through the blood.

There are no known human cases with transmission from other animals or animal bites, only by mosquito bites of infected mosquitoes. Although it is still recommended that, if you find a dead bird in an area known to have the virus (especially in late August to early September in the Northern Hemisphere when the most infected mosquitoes are active), you should not touch it with bare hands and do contact the local health department so they can record the case and give instructions on proper disposal of the dead bird.

It is not transmitted from person to person or through touching someone with the virus.

Prevention:Vaccines:

There is no human vaccine for prevention yet. However, the US Centers for Disease Control and Prevention (CDC) continues to work on steps toward future development.

Avoid mosquito bites! Avoid Exposure:

1. Reduce the numbers of mosquitoes in your environment:

Keep their breeding areas limited.

One of the more effective ways is with keeping pooling water dry, e.g., birdbaths and small fountains and pools should have the water changed once a week minimally. Punch holes in tire swings so water doesn't collect to stagnate, empty kids' swimming pools, plant pots, trash bins, fill holes and low areas where standing water can collect and stagnate. If ditches do not flow and contain stagnant water for a week or longer, report this problem to a mosquito control district or public health office. Clean debris from rain gutters, remove standing water from flat roofs, tarps and canvases, and repair leaks around faucets and air conditioners.

2. Don't use "bug zappers":

It has been shown that they actually attract mosquitoes into your yard. In addition, most insects killed by bug zappers include moths, beetles and other harmless and helpful bugs - not mosquitoes.

3. Encourage native mosquito-eating insects and animals:

Such as birds, bats, hummingbirds, frogs, dragonflies, etc. Although, the info on this is mixed, according to the American Mosquito Control Association:

There is no proof that bats, purple martins, or other animals that eat insects are able to eat enough adult mosquitoes to make a difference. One reason for this is because purple martins fly and eat during the day and most mosquitoes are active at night. In addition, most bats eat June bugs and moths, but do not eat mosquitoes. Also, bats can transmit the rabies virus and encouraging them to live in your yard could pose a health risk to your family and neighbors."

4. Use pesticides sparingly if at all.

5. Use repellents:

Those with the active ingredient DEET are proven most effective and also safe when used according to label directions. Do not use DEET (or other repellents made for people) on your dogs. They can become ill from licking it. Talk to your veterinarian for safe repellents for your pets.

6. Wear protective clothing:

When outside, wear long sleeves and long pants that are light colored (mosquitoes seem to be more attracted to darker colors). Spray clothing with repellent as well.

7. Avoid being outside when mosquitoes are most active:

From dusk to dawn.

8. Screening/Mosquito Netting:

Install and keep screens on windows and doors closed and in good repair to keep the mosquitoes from coming into the house. Use mosquito netting when sleeping in homes with poor control through other means, especially around the beds of infants, children, and older adults. Also remember to use these when camping or sleeping outdoors.

Infections in Animals:

WNV can infect just about any animal, but they rarely, if ever, become sick from the virus.

Do not use DEET (or other repellents made for people) on your dogs or other pets. They can become ill from licking it. Talk to your veterinarian for safe repellents to use for your pets.

There are no preventive vaccines for cats and dogs, but there is a vaccine for horses.

Pets and animals do not transmit the virus to humans, even if the animals inflict a bite.

Dogs:

Dogs can be infected from mosquito bites, although it is unlikely that most pet owners would notice any unusual symptoms or behavior in dogs that become infected, and the reported cases are infrequent. Infected dogs showed no symptoms after experimental infection. Treatment is as for humans, supportive care for the symptoms and with standard veterinary practices for animals infected with a virus.

Cats:

Can be infected from mosquito bites, although it is unlikely that most pet owners would notice any unusual symptoms or behavior in cats that become infected. But some mild, nonspecific symptoms (such as slight fever or lethargy) were seen in infected cats during the first week after infection. Treatment is as for humans, supportive care for the symptoms and with standard veterinary practices for animals infected with a virus.

Cats have also become infected with the virus after eating experimentally infected mice.

Horses:

Horses appear to be the only domestic animal severely affected by West Nile virus. They can be infected from mosquito bites. Some horses have had severe illness, or even have died from the virus, but most horses recover. The virus has been found in the horses' blood for only a few days. Treatment is as for humans, supportive care for the symptoms and with standard veterinary practices for animals infected with a virus.

Signs in horses:

The most frequent signs are ataxia (gait issues), weakness of limbs, recumbency, muscle twitching, and death.

Other animals at risk:

1. Birds:

Different types of birds in different locations are affected. For example, in TX, mostly blue jays and crows are involved.

Zoo birds, such as flamingos, may also be affected.

Some wild birds develop severe clinical signs.

There is no evidence that the virus adversely affects emus or other ratites.

2. Rabbits:

WNV has been reported in domestic rabbits.

3. Bats.

4. Chipmunks.

5. Skunks.

6. Squirrels.

7. Other domestic animals:

The virus may infect other domestic animals, but they do not show any clinical signs.

Sources: Centers for Disease Control and Prevention (CDC), National Institutes of Health (NIH), Texas Department of State Health Services Infectious Disease Control Unit, various medical literature sources.