How do people and animals get West Nile virus?

West Nile virus is transmitted to people and animals (birds and horses) by infected mosquitoes. Only certain species of mosquitoes carry the virus and very few mosquitoes are actually infected.

Are there other ways of getting West Nile virus?

In rare instances, West Nile virus can be transmitted through blood transfusion, organ transplants, and from mother to fetus and breast feeding infants. Pregnant and nursing mothers are encouraged to avoid mosquitoes. Consult a physician for additional information.

What are the symptoms?

Most people who are infected with West Nile virus have no symptoms. Of those who become ill, symptoms may include fever, headache, body aches, nausea, skin rash, and/or swollen lymph nodes. Symptoms will generally last a few days. In severe cases, encephalitis (inflammation of the brain), meningitis (inflammation of the membrane surrounding the brain) or inflammation of both the brain and the membrane may occur. Severe symptoms may include high fever, headache, neck stiffness, disorientation, coma, tremors, paralysis, and possibly death. Neurological damage may be permanent. At greatest risk are people over the age of 50, the elderly, and those who have weakened immune systems. The incubation period, or the time between the mosquito bite and the onset of illness, ranges from 3-15 days in humans. It is estimated that one in 150 who are infected with West Nile virus will require hospitalization.

Is there a vaccine for humans?

No, currently there is no WNV vaccination for humans.

Which animals get West Nile virus?

An infected mosquito can bite any animal, but not all animals will become infected. The disease most often affects birds (crows, ravens, magpies, and jays), but occasionally causes disease in other animals as well.

If you find a dead bird, particularly a crow or other corvid (i.e. raven, jay, or magpie) please call the California Department of Public Health hotline at 1-877-WNV-BIRD. Not all birds will qualify for testing, but they will record all reports of dead birds.

To move or discard a carcass, wear rubber or latex gloves. If gloves are not available, use a plastic bag turned inside-out over your hand and invert the bag to surround the bird. Seal and discard in the trash if the bird will not be picked-up for testing.

Horses are also susceptible to West Nile virus. The disease does not seem to be specific to a particular breed or age of horse. Many horses infected with West Nile virus will not develop any illness. Of those that do become ill, approximately 30% die or must be destroyed. If your horse becomes infected, it is not contagious to you or to other horses. Clinical signs can include a lack of coordination, stumbling, circling, falling, weakness or partial paralysis of limbs, muscle twitching (especially around nose and lips), an inability to rise, and grinding teeth. There are two different vaccinations available for horses. The timing of these vaccines is critical because they must be administered prior to disease exposure. Contact a veterinarian for advice.

Does West Nile virus affect dogs and cats?

Dogs and cats rarely show illness if infected with West Nile virus. The National Animal Poison Control Center warns that insect repellant should not be used on pets. Cats are highly sensitive to the chemicals, and both dogs and cats lick themselves and could ingest toxins from the repellents. So far, cats and dogs have been fairly resistant to the virus.

What can you do to help?

Since mosquitoes breed in standing water, you can help stop the mosquito life cycle and West Nile virus transmission by eliminating standing water on your property. Eliminate standing water by dumping or draining water in negelected swimming pools, ponds, rain barrels, discarded tires, buckets, or anything container capable of holding water for more than a few days. You can significantly contribute ot the fight against West NIle virus by following these simple actions. Remember, if they can't breed, they can't bite.

How to protect yourself and your family

• Avoid activity at dawn and dusk when mosquitoes are most active
• Apply mosquito repellent containing the active ingredient DEET when outside

• Wear protective clothing (loose, light colored, long sleeve shirts and pants)

Summary of WNV Positives For 2012

	GLACVCD	CA State
Humans	95/2 deaths	476/ 19 deaths
Horses	0	22
Dead Bird Surveillance	70	1,644
Mosquito Pools	318	2,894
Sentinel Chickens	26	540

Click here to view details on WNV activity for the year 2012

Summary of WNV Positives For 2011

	GLACVCD	CA State
Humans	44/2 deaths	158/ 9 deaths
Horses	0	15
Dead Bird Surveillance	159	688
Mosquito Pools	448	2,087
Sentinel Chickens	40	391

Summary of WNV Positives For 2010

	GLACVCD	CA State
Humans	1	111/6 deaths
Horses	0	19
Dead Bird Surveillance	31	416
Mosquito Pools	56	1,305
Sentinel Chickens	0	281

Summary of WNV Positives For 2009

	GLACVCD	CA State
Humans	8/1 death	112/4 deaths
Horses	0	18
Dead Bird Surveillance	38	515
Mosquito Pools	91	1,063
Sentinel Chickens	0	443

Summary of WNV Positives For 2008

	GLACVCD	CA State
Humans	83/15 deaths	443/21 deaths
Horses	0	32
Dead Bird Surveillance	259	2,569
Mosquito Pools	472	2,002
Sentinel Chickens	37	585

Summary of WNV Positives For 2007

	GLACVCD	CA State
Humans	32/3 deaths	378/16 deaths
Horses	0	28
Dead Bird Surveillance	115	1,395
Mosquito Pools	88	1,007
Sentinel Chickens	14	510

Summary of WNV Positives For 2006

	GLACVCD	Los Angeles County	CA State
Humans	7/0 deaths	13/0 deaths	272/6 deaths
Horses	0	0	57
Dead Bird Surveillance	58	93	1,404
Mosquito Pools	78	78	833
Sentinel Chickens	18	38	640

Summary of WNV Positives For 2005

	GLACVCD	Los Angeles County	CA State
Humans	22/0 deaths	47/0 deaths	935/18 deaths
Horses	5/3 deaths	10/6 deaths	456/200 deaths
Dead Bird Surveillance	135	173	3,044
Mosquito Pools	179	218	1,242
Sentinel Chickens	6 flocks (16 chickens)	77	793

Summary of WNV Positives For 2004

	GLACVCD	Los Angeles County	CA State
Humans	180/4 deaths	331/14 deaths	830/28 deaths
Horses	8/5 deaths	16/8 deaths	540/230 deaths
Dead Bird Surveillance	645	840	3,232
Mosquito Pools	331	408	1,136
Sentinel Chickens	44	166	805

For more information on West Nile virus statistics, visit www.westnile.ca.gov.