SAN FRANCISCO (KTVU/BCN) - Three Zika virus cases confirmed in the East Bay today have brought the total number of reported cases in the Bay Area to five, according to area health officials.
Alameda County public health officials said today the county has one confirmed case and Contra Costa County health officials said they have two confirmed cases.
"Only about 20 percent of people who are affected by the Zika virus show symptoms. They're usually fairly mild, so fever, joint pain, sometimes a rash, sometimes red eyes or conjunctivitis. They're usually quite mild, they last from several days to a week," explains Contra Costa County communicable diseases program chief, Erika Jenssen.
Contra Costa County health officials are saying little about the people who got Zik; including their age, where they live, nor whether the people were pregnant.
"There is no risk here in Contra Costa if someone has Zika, because we don't have the mosquitos that transmit Zika,” said Jenssen.
San Francisco public health officials on Thursday said a resident tested positive for the Zika virus.
Napa County health officials said on Wednesday the California Department of Public Health confirmed a case in that county.
County healthy officials in all four counties said there is no threat to public health.
The San Francisco Department of Public Health received confirmation from the California Department of Public Health on Feb. 4.
Health department spokeswoman Rachael Kagan said officials delayed announcing the confirmed case to the public because the case posed no public health threat.
Department officials may reconsider that policy and the department is working to with San Francisco communities of residents who are from countries where transmission is occurring.
The resident of San Francisco who contracted the virus has recovered.
The virus most notably appears to be linked to a birth defect called microcephaly, which causes children to be born with smaller heads, San Francisco health officials said.
Zika virus is usually spread by mosquitoes, but doctors have also identified cases in which transmission has occurred through sexual intercourse.
San Francisco health officials said the transmission of the disease is not occurring in the U.S., but U.S. health officials are warning people, especially pregnant women, to consider delaying travel plans to countries where transmission is occurring.
Those countries are mostly in Latin America and Caribbean, including Puerto Rico. Brazil has reported an increase in cases of microcephaly.
Officials with the Centers of Disease Control are encouraging people who are traveling to countries where transmission is occurring to protect themselves from mosquito bites.