Each of the deaths has involved a person under the age of 65. Five individuals had underlying medical conditions and one person had no known underlying medical conditions, according to the San Mateo County Health System.
Five of those flu cases have been confirmed as H1N1, or swine flu, while information on the type of strain was not available for one case, according to the health system. No information was released on the age or gender of the victims.
The county has had 20 flu-related intensive care unit hospitalizations this season. Bay Area county health departments reported at least 35 flu deaths have occurred this winter in the region. In San Francisco, three influenza-related deaths of nonelderly adults were reported this season.
The first death in December was confirmed to be due to swine flu, the San Francisco Department of Public Health said. The third victim was someone who was not elderly but who had an underlying medical condition, according to the department.