Aggressive Mosquitoes That Can Transmit Zika Virus Are Present in SoCal: Public Health Officials

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The type of aggressive mosquitoes that transmit the rapidly spreading Zika virus are present in Los Angeles County and elsewhere in California, officials said Wednesday.

Aedes mosquitoes were identified in the San Gabriel Valley and in eastern part of L.A. County in 2011. They prefer to feed on humans, and will follow their desired hosts indoors, county Interim Health Officer Dr. Jeffrey Gunzenhauser said at a news conference.

Though no patients in the U.S. have been infected locally by mosquitoes bearing Zika, Gunzenhauser said it was critical that the aggressive, non-native pests be eliminated locally.

Dr. Jeffrey Gunzenhauser speaks about Zika virus in Los Angeles on Feb. 3, 2016. (Credit: KTLA)

Dr. Jeffrey Gunzenhauser speaks about Zika virus in Los Angeles on Feb. 3, 2016. (Credit: KTLA)

That’s in part because it’s possible that an infected patient could come to Southern California and be bitten by an Aedes mosquito, and then the bug could spread the virus to new patients here.

“We have to take action,” Gunzenhauser said. “If someone comes here who’s infected and gets bitten by these mosquitoes, it’s possible that we could set up chain of transmission here in Los Angeles County. We think that’s unlikely, but we want to take actions to prevent that.”

Up to 80 percent of people who contract Zika show no symptoms, he said. Those who do show symptoms experience fever, a rash, joint pain, or conjunctivitis. The relatively mild symptoms can resolve in a week or less.

A Health Ministry agent finds a larva of Aedes aegypti mosquito, vector of the Zika, Dengue and Chikungunya viruses, during an operation to fight them in Sao Paulo, Brazil on Feb. 3, 2016. (Credit: NELSON ALMEIDA/AFP/Getty Images)

A Health Ministry agent finds a larva of Aedes aegypti mosquito, vector of the Zika, Dengue and Chikungunya viruses, during an operation to fight them in Sao Paulo, Brazil on Feb. 3, 2016. (Credit: NELSON ALMEIDA/AFP/Getty Images)

The primary reason that the virus has gained such attention — and on Monday was declared an international public health emergency by the World Health Organization — is its apparent but still unconfirmed connection to microcephaly in infants born to pregnant woman believed to have contracted Zika. Microcephaly, in which babies’ heads are small due to underdeveloped brains, can lead to severe physical and mental disabilities.

Pregnant woman are strongly advised to check the Centers for Disease Control and Prevention’s travel advisories and defer travel to locations where Zika is present.

Locally, Gunzenhauser and the regional vector control district’s general manager urged residents to eliminate mosquito-breeding areas on their property. Any container in which standing water can collect should be drained, said Truc Dever of the Greater Los Angeles County Vector Control District.

Aedes mosquito eggs can survive for years, officials said.

In addition to Zika, the mosquitoes can also transmit dengue and chikungunya viruses.

A California Department of Public Health map shows distribution of the species of mosquitoes that can transmit Zika virus.

A California Department of Public Health map shows distribution of the species of mosquitoes that can transmit Zika virus.

Two species -- Aedes aegypti aka yellow fever mosquitoes, and Aedes albopictus mosquitoes aka Asian tiger mosquitoes -- has been identified in 12 counties, including Orange, Riverside and San Bernardino as well as Los Angeles, according to state data from December.

One patient in L.A. County has been documented as having Zika, and specimens from several other patients are being tested, Gunzenhauser said. The patient, an adolescent girl who has fully recovered, had traveled to El Salvador in November, he said.

That case was first reported last week. On Tuesday, the CDC confirmed that a Zika case in Texas had been sexually transmitted by an ill partner, who had traveled to Venezuela, to an individual in Dallas County.

A similar sexual transmission occurred several years ago in Colorado, Gunzenhauser said.

Those types of reports, as well as links to blood transfusions, need to be investigated, Gunzenhauser said. But locally, authorities are most concerned about mosquito-borne transmission, he said.

“Our focus remains on mosquitoes as the key vector and truly the target that will allow us to prevent this condition from becoming established here in Los Angeles County,” the doctor said.