SAN DIEGO -- Forty-four children taken to Rady Children's Hospital in the past two weeks have tested positive for the H1N1 virus, including at least four who attended summer camps in the county, it was reported Wednesday.

As of early Wednesday, there have been 531 confirmed cases of swine flu, according to the county Health and Human Services Agency.

Swine flu is surfacing at children's camps across the county, The San Diego Union-Tribune reported.

At least 27 asthmatic children who attended a pair of American Lung Association Camps at Camp Marston in Julian and another facility in Livermore in Northern California came down with the illness, the Union-Tribune reported.

Some camps, including the Muscular Dystrophy Association's camp at Camp Cuyamaca in Descanso, have been canceled or delayed because of the virus, but most have kept their schedules, according to the newspaper.

On Tuesday, the number of fatal swine flu cases reported in the county rose to four, with the latest victim being a 50-year-old woman. She died June 29, six days after being admitted to Paradise Valley Hospital in National City.

The woman, whose name was not released, had underlying respiratory and immune-system problems that played a role in her death, the Union-Tribune reported.

County Public Health Officer Wilma Wooten said it was "particularly important" for people with "underlying medical conditions" to promptly seek treatment from a physician if they experience flu symptoms.

She reiterated health officials' call for common-sense precautions: cover your mouth when coughing or sneezing, wash your hands frequently and thoroughly, and stay home when sick to help prevent the spread of the disease.