Watch out for mosquitoes — West Nile Virus is circulating in Alameda County

Mosquito photo

Public health officials are advising residents to take proactive steps to protect themselves against mosquitoes, which, despite their small in size, harbor a power that could prove fatal to its human prey.

The Alameda County Mosquito Abatement District actively monitors mosquito activity by strategically deploying traps in the area. These traps provide insight into the extent of disease transmission by local mosquitoes. This year, the district has recorded five instances of mosquitoes and seven instances of dead birds testing positive for West Nile Virus, surpassing the cumulative count from the previous four years when the district counted between zero and eight total instances of the disease.

“That’s due to all the rain,” Judith Pierce, public outreach coordinator for the district, told the East Bay Echo.

Mosquitoes are reliant on water for their life cycle, and any receptacles or items collecting water can serve as breeding grounds. Getting rid of the standing water effectively gets rid of the mosquitoes. In cases of large pools turning into breeding sites, individuals can reach out to the mosquito abatement district for free water treatment, thereby preventing the need for insecticide spraying in the region.

“Different scenarios will require different treatments,” Pierce said. “We focus on things that are ecologically sustainable and environmentally reasonable.”

Mosquitoes serve as critical vectors for various diseases, including malaria, Brian Byrd, a professor of environmental health sciences at Western Carolina University, said during a recent SciLine media briefing. That’s because female mosquitoes require a blood meal to lay eggs and can contract different diseases depending on their chosen host —whether an infected bird, human or other animal. Once infected, a mosquito becomes infectious within five to 10 days.

“From a global perspective (malaria’s) where the largest burden of mosquito-borne disease comes from,” Byrd said. “But also, particularly viruses, these are called arboviruses, or arthropod borne viruses. And these are ones like West Nile virus, La Crosse encephalitis virus, dengue virus, Zika virus, and the list goes on.”

West Nile Virus, not native to the country, was introduced to the United States in 1999 and reached California around 2004, Jason Rasgon, a professor of entomology and disease epidemiology at Pennsylvania State University, told the East Bay Echo. Rasgon, who has studied the virus extensively since its introduction, mentioned that while there’s no vaccine, most infections result in asymptomatic cases, with only a few individuals experiencing mild symptoms such as a slight fever or characteristic rash. The most vulnerable to severe effects are generally older adults and individuals with compromised immune systems.

“Most people will be fine,” Rasgon said. “Most people won’t even know they have it.”

The mosquito species most likely to transmit West Nile Virus in the Bay Area also displays a preference for feeding on birds over humans, Pierce said.

“We test dead birds because birds, especially crows, ravens and scrub jays, are especially vulnerable to West Nile Virus,” Pierce said. “Usually they get this really awful encephalitis so their brain just melts essentially.”

While West Nile is something people should be aware of and take precautions about, Rasgon said it’s not something to panic over, especially if you take steps to protect yourself.

Tips to protect yourself against mosquitoes

  • Wear mosquito repellents recommended by the Centers for Disease Control and Prevention and approved by the U.S. Environmental Protection Agency
  • Avoid being unprotected outside, particularly at dawn and dusk when mosquitoes are most active
  • Wear long sleeves and long pants in mosquito-heavy areas
  • Get rid of any pools of standing water
  • Report dead birds for testing at, where you can also find more information

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