The California Department of Health said three sentinel chickens in San Benito County tested positive for West Nile virus in August, making it the first indication of the virus in the county in 2023. In 2020 sentinel chickens in the county also tested positive.Â
Mallory Schmitt, epidemiologist and public information officer with San Benito County Environmental Health, told BenitoLink the chickens were located in north county and the rain earlier this year made conditions ripe for mosquitos, which are vectors for the virus, to breed.
According to the World Health Organization West Nile virus was first documented in the U.S. in 1999 following reported deaths of corvids (crows, jays, magpies) in New York. It found its way to California in 2003.
John Hopkins University website notes the virus can infect humans, birds, mosquitoes, horses and other mammals. Very rarely, the virus can spread in transfused blood, a transplanted organ, or through the placenta to an embryo or fetus.
West Nile virus occurs in late summer and early fall in mild zones. It can also occur year-round in southern climates. Most often, it causes mild, flu-like symptoms, which usually appear within three to 14 days of contracting it. But, the virus can cause life-threatening illnesses, such as:
- Encephalitis (inflammation of the brain)
- Meningitis (inflammation of the lining of the brain and spinal cord)
- Meningoencephalitis (inflammation of the brain and its surrounding membrane)
According to the California Department of Public Health, there have been 75 reported human cases of West Nile virus in the state as of Sept. 1. Of those cases five were fatal. Among the surrounding counties with reported human cases are Santa Clara (1), Stanislaus (1) and Merced (2).
California averaged 198.8 reported human cases between 2018 and 2022.
About 20% of the people who become infected will develop West Nile fever. These are the most common symptoms of West Nile fever:
- Fever
- Headache
- Body aches
- Skin rash on trunk of body
- Swollen lymph glands
The more severe form of the West Nile virus affects mostly older adults. It occurs when the virus crosses the blood-brain barrier and can cause:
- Headache
- High fever
- Neck stiffness
- Stupor (a state of impaired consciousness, extreme lethargy, and reduced reactivity to outside stimuli)
- Disorientation
- Coma
- Tremors
- Convulsions
- Muscle weakness
- Paralysis
According to the Centers for Disease Control and Prevention, West Nile virus is most commonly spread to people from infected mosquitoes and is not spread by:
- Coughing, sneezing, or touching
- Touching live animals
- Handling live or dead infected birds
- Eating infected animals
To prevent West Nile virus the CDC recommends the use of an Environmental Protection Agency-registered insect repellent.
The CDC website states EPA-registered insect repellents contain one of the active ingredients listed below. When used as directed, they are shown to be safe and effective, even for pregnant and breastfeeding women.
- DEET
- Picaridin (known as KBR 3023 and icaridin outside the U.S.)
- IR3535
- Oil of lemon eucalyptus (OLE)
- Para-menthane-diol (PMD)
- 2-undecanone
Tips for babies and children:
- Dress children in clothing that covers arms and legs.
- Cover strollers and baby carriers with mosquito netting.
- When using insect repellent on a child:
- Always follow label instructions.
- Do not use products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) on children under three years old.
- Do not apply insect repellent to a child’s hands, eyes, mouth, cuts, or irritated skin.
- Adults: Apply insect repellent onto your hands and then apply to a child’s face.
- Wear loose-fitting, long-sleeved shirts and pants and treat clothing and gear
- Use 0.5% permethrin to treat clothing and gear (such as boots, pants, socks and tents) or buy permethrin-treated clothing and gear.
- Permethrin is an insecticide that kills or repels mosquitoes.
- Permethrin-treated clothing provides protection after multiple washings.
- Read product information to find out how long the protection will last.
- If treating items yourself, follow the product instructions.
- Do not use permethrin products directly on skin.
Other steps for controlling mosquitoes:
Use screens on windows and doors. Repair holes in screens to keep mosquitoes outdoors.
- Use air conditioning, if available.
- Stop mosquitoes from laying eggs in or near water.
- Once a week, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers.
- Check for water-holding containers both indoors and outdoors.
The San Benito County Health Department website notes that human cases in the county are rare but has a mosquito abatement program which uses different methods to control the risk of disease, including surveillance, prevention and control of mosquito populations.
To report problems with mosquitos, or for advice on mosquito management contact the Health Department office at (831) 637-5344. To report a dead bird, contact the California Department of Public Health at (877) 968-2473 or file a report here. For general health questions on West Nile virus, call San Benito County Public Health Services at (831) 637-5367.
Schmitt noted the importance of having dead birds tested and removing any standing or stagnant water in the vicinity.
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