Mosquitoes capable of carrying the Zika virus continue to spread in California.
On Wednesday, officials in Yolo County in Northern California announced that an individual who had traveled abroad had tested positive for the virus–the sixth person in the state to do so since 2013, according to the San Francisco Chronicle.
Thus far, all of the cases in California involve people who had traveled to Latin America, where the virus is carried by mosquitoes.
There are concerns that the virus could also spread along other vectors, including through sexual transmission and blood transfusions, and perhaps through other body fluids as well.
Zika causes mild flu-like symptoms, and some of those infected may feel no symptoms at all. However, in pregnant women, it is associated with microcephaly–the birth of babies with small skulls, which causes brain damage and requires extensive surgeries and rehabilitation.
The Aedes aegypti mosquito is an invasive species that spreads Zika, and bites during the day. In California, the species has already been found in Orange County and is spreading to other parts of the state, taking advantage of unusually wet conditions caused by the El Niño weather pattern, which has brought rain to much of the drought-stricken state.
Officials in Santa Cruz County, for example, expect the mosquitos to spread to their region soon.
None of the Aedes aegypti mosquitos in the state have been found to carry Zika, but officials expect that to change.
“We think it’s only a matter of time before the viruses and the mosquitoes in California get together, and that we have infected mosquitoes, and that there’s local transmission. But this won’t be a very frequent occurrence,” said Paul Binding, Santa Cruz mosquito control director, in an interview with Central Coast-based NBC affiliate KSBW.