Invasive mosquitoes discovered in Bay Area can transmit Zika, dengue, and yellow fever

LIVERMORE, Calif. - An invasive species of mosquito was discovered in Alameda County earlier this month. Officials say the Aedes aegypti mosquitoes were found in Livermore on August 8 and that they can transmit dengue, Zika and yellow fever. 

Invasive species 

What we know:

The Alameda County Mosquito Abatement District confirmed the mosquitoes' presence, saying this marks the first detection of the species in the city. The district issued a news release about the mosquitoes on Monday and said they are working with city officials and volunteer groups to inform residents and to inspect properties. 

District staff are going door-to-door in two detection zones to inspect and treat potential mosquito breeding sites. They are also conducting what they call "intensive follow-up trappings." 

District General Manager Ryan Clausnitzer said they are inspecting both public and private properties and are seeing cooperation from Livermore residents and business owners. 

"The quickest way to prevent this annoying and potentially dangerous mosquito species from becoming established is to act now," said Clausnitzer. "We urge residents to grant yard access so we can ensure no one is accidentally breeding mosquitoes."

"If Aedes aegypti becomes established in Alameda County, it could threaten public health and quality of life," officials said. 

Officials said the two detections were in separate locations. One was near Livermore Water Reclamation Plant between Isabel Avenue and Jack London Street. The second detection was southeast of Jack Williams Park, between Hommes Street and Alden Lane. District officials said their staff may be seen in the area in their uniforms with official logos and wearing identification. 

About this mosquito

Officials say Aedes aegypti is an aggressive, daytime-biting mosquito that often targets ankles. The species is considered a container breeder, known for laying eggs just above the waterline in small artificial sources like buckets, pet dishes, fountains, birdbaths, plant saucers and old tires. 

Officials stressed that this species of mosquito is highly-aggressive during daytime hours. 

The species is not native to California, but can be found in at least 26 California counties; Some of those counties are nearby, officials said. 

The eggs are quite resilient and can survive for more than a year without water. One preventative measure that can be employed is to scrub containers. This helps dislodge the eggs and prevents them from moving to new locations, district officials said. 

The tiny mosquito eggs can be mistaken for dirt or seeds. Officials say this species can develop from egg to adult in the amount of water held by a bottle cap. 

"The District's goal is to prevent this species from becoming permanently established in Alameda County," district officials said. "Adult mosquitoes are less than a quarter-inch long, with black and white stripes on their backs and legs. They typically bite people and do not travel far—generally less than 300 feet from where they hatch."

Health notes 

When Zika virus first emerged in the Americas in 2015, an association between the virus and microcephaly was first described by the World Health Organization. This was a congenital malformation that presented itself in the form of smaller head size. WHO said cases of Zika virus globally declined from 2017 onwards. 

Dengue is a viral infection that also spreads from mosquitoes to humans. Most people with dengue will not present symptoms. For those who do, WHO says the most common symptoms are high fever, headache, body aches, nausea, and a rash. In severe cases, dengue can be fatal. There is no specific treatment for dengue as the focus is on treating pain symptoms, the health organization says. 

With yellow fever, a vaccine preventable disease, this virus can be transmitted by mosquitoes, ticks or other arthropods, WHO says. Symptoms include fever, muscle pain, headache, loss of appetite, nausea or vomiting. A small percentage of patients can enter a second more toxic phase of the virus within 24 hours of recovering from their initial symptoms. Some 50% of patients die in about a week to 10 days in the second phase. 

What you can do

Residents in Livermore and throughout Alameda County are being asked to inspect their properties for standing water, which can be used as mosquito breeding grounds. 

Protect yourself 

• Apply insect repellents containing EPA-registered ingredients such as DEET, picaridin, IR3535, or oil of lemon eucalyptus.
• Wear long-sleeved shirts, pants, socks, and shoes when mosquitoes are most active.
• Ensure window and door screens are in good condition.
• Report daytime mosquito activity immediately to the Alameda County Mosquito Abatement District at (510) 783-7744 or www.mosquitoes.org.

For questions or concerns, district officials say to visit www.mosquitoes.org or call (510) 783-7744.