Several more Bay Area cases of the Zika virus were either reported or confirmed Thursday, one day after Napa County public health officials confirmed a pregnant woman who had traveled to Central America had contracted the virus.
The San Francisco Department of Public Health said Thursday that a San Francisco resident last month had tested positive for the Zika virus.
Department spokeswoman Rachael Kagan said the state's public health department confirmed the case with the San Francisco's public health officials on Feb. 4.
Kagan said the person is fully recovered and doing well.
In Contra Costa County, public health department spokeswoman Victoria Balladares said two confirmed cases have been recorded -- one last Thursday and one in early February.
This 2006 photo provided by the Centers for Disease Control and Prevention shows a female Aedes aegypti mosquito in the process of acquiring a blood meal
This 2006 photo provided by the Centers for Disease Control and Prevention shows a female Aedes aegypti mosquito in the process of acquiring a blood meal from a human host. On Friday, Feb. 26, 2015, the U.S. government said Zika infections have been confirmed in nine pregnant women in the United States. All got the virus overseas. Three babies have been born, one with a brain defect. (James Gathany/Centers for Disease Control and Prevention via AP) ( James Gathany )
Both women said all of the individuals with Zika had returned from traveling to a country where the Zika virus is present. But they said their health departments had not released the information before now because there was no risk of transmission to the local community.
"The mosquitoes that carry the Zika virus are not present in Contra Costa County," Balladares said.
The Alameda County Public Health Department website confirmed that an Alameda County resident, who had been traveling in a Zika affected country, had tested positive for the virus last month. But they have ruled that to be a 2015 case. San Mateo and Santa Clara County public health officials said there are no confirmed Zika cases. No information was available about Marin, Sonoma or Solano counties.
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The state's first confirmed Zika case was reported in Yolo County last month.
The mosquito-borne virus has been linked to a rare birth defect that results in an abnormally small head.
The U.S. Centers for Disease Control and Prevention said Brazil has reported that an increased number of people infected with the virus also have Guillain-Barré syndrome, an immune system disorder.
State public health officials have confirmed six cases in the state, and update those numbers each Friday.
Zika virus is primarily transmitted to people by Aedes aegypti and Aedes albopictus mosquitoes, the same mosquitoes that can transmit dengue and chikungunya viruses. These mosquitoes -- which are not native to California -- have been identified in 12 California counties. Only Aedes aegypti has been found in the Bay Area, in San Mateo and Alameda counties. There are no known cases where the mosquitoes have transmitted the Zika virus in California.
The six confirmed cases of Zika virus in California were acquired in other countries.
Contact Tracy Seipel at 408-920-5343. Follow her at Twitter.com/taseipel.