The woman died Tuesday evening at an Alameda County hospital where she was taken after her condition worsened in a Marin County hospital, Goel said.
"We are saddened by the death of a member of our community," Goel said in a statement. "Our thoughts and sympathies go out to her family and friends."
There have been 49 cases of the H1N1 swine flu in Marin County, 24 of them probable and 25 confirmed, Goel said. Like other areas of the state, Marin County public health officials have seen an increase in the number of H1N1 cases in the past two weeks.
"We anticipate that we will continue to see more cases over the next several weeks and months now that the H1N1 virus has become well established in California," Goel said.