Most mosquito bites are relatively painless, annoying but not terrifying.
Yet, health organizations indicate there may be new and profound dangers associated with invasive mosquitoes that have found their way into California.
The new threat is Zika virus, which is transmitted to people by Aedes aegypti and Aedes albopictus mosquitoes (also known as yellow fever mosquito and Asian tiger mosquito, respectively), and since early last year, the virus has spread across Brazil and other countries and territories from South America northward into Mexico and the Caribbean.
Originally discovered in Africa and thought to be a cause of only very mild disease, Zika has become a much bigger problem in recent years, causing outbreaks since 2007 across many islands in the Pacific Ocean. The biggest cause for alarm has been the evidence emerging from South and Central America that point to Zika as a likely cause of neurological impairment in adults and microcephaly – small head and small brain – in newborn infants. Because of this possible link, the Department of Public Health recommends travel precautions for pregnant women and women trying to become pregnant.
The main mosquitoes that transmit Zika virus are not native to California, but they have been found here in growing numbers since 2011, and local mosquito control agencies and the California Department of Public Health are working constantly to track and limit their spread. These mosquitoes are now found throughout much of Southern California, north to Madera County in the Central Valley and with smaller populations near the southern end of the San Francisco Bay.
In the areas where these mosquitoes are found, there is a risk that local transmission of Zika virus could occur if the mosquitoes were to bite an infected traveler who has this virus in their blood.
“We are fortunate in California to have some of the world’s best mosquito control programs, and they are actively trying to reduce mosquito populations,” said Dr. Chris Barker, a UC Davis researcher in the School of Veterinary Medicine’s Department of Pathology, Microbiology and Immunology who studies the epidemiology of mosquito-transmitted diseases and conducts NASA-funded research on the Zika virus vectors in our state. “For these programs to be most effective, it is essential that information on newly diagnosed Zika cases should be conveyed to mosquito control and public health officials immediately to allow for the fastest possible response.”
It is important to note that all nine confirmed cases in California, as of Feb. 12, have been documented with Zika infections after traveling outside of the United States, and, in winter, risk for local transmission is lowered due to cooler temperatures and smaller numbers of mosquitoes.
“The weather definitely affects mosquito abundance and distribution,” said Dr. Vicki Kramer, Chief of Vector-Borne Disease Section with the Department of Public Health. “There’s always going to be a connection between weather and mosquitoes and mosquito-borne diseases. Mosquitoes, in general, are less of a concern this time of year. As it heats up, the concerns with mosquitoes, as with most insects, increases.”
Tips to avoid mosquito bites include:
- Apply a repellent that contains DEET, Picaridin, IR3535, or Oil of Lemon Eucalyptus. Protection time varies on the type and percentage of active ingredient in these products.
- Wear protective clothing, such as long-sleeved shirts and pants.
- Check and repair all window screens and screen doors to keep mosquitoes out of the house.
- Minimize outdoor activities at dawn and dusk when mosquitoes are most active.
“The public can reduce their own risk of mosquito biting through use of repellents and wearing long clothing, and they can keep mosquitoes and the risk for local Zika virus transmission low by removing all sources of standing water from their own backyards,” said Barker. “Most people think of mosquitoes as one thing, but we have many species in California that vary in their ability to transmit pathogens. Know what the daytime-biting mosquitoes that transmit Zika virus looks like, and if you notice them in your area, report them to your local mosquito control agency. This is a key way that the agencies find new populations and track the mosquitoes’ spread across the state.”
The Department of Public Health details additional information on mosquitoes and mosquito-borne diseases here.