Deaths from influenza outbreak shoot up in California Toll in outbreak nearing total for last year's season - severity blamed on re-emergence of H1N1-related strain

Infectious disease experts say people should still get flu vaccines, which take about two weeks to reach full strength. Infectious disease experts say people should still get flu vaccines, which take about two weeks to reach full strength. Photo: Paul Chinn, The Chronicle Photo: Paul Chinn, The Chronicle Image 1 of / 1 Caption Close Deaths from influenza outbreak shoot up in California 1 / 1 Back to Gallery

The number of deaths caused by this year's influenza outbreak shot up in California last week and appears to be very close to matching the death toll from the flu for all of last year.

The state has confirmed 45 flu-related deaths in adults under age 65 and is investigating another 50 deaths that were probably caused by the flu. Two of those deaths, including one in San Mateo County, were children. At least 17 under-65 adults have died from the flu in the Bay Area.

Statewide, the numbers far surpass last year's reports. By mid-January in 2013, the state had five confirmed flu deaths in adults younger than 65; there were only 106 such deaths all of last season.

"Influenza activity continues in earnest across the state," said Dr. Gil Chavez, deputy director of the Center for Infectious Diseases with the California Department of Public Health, in a media briefing. "So far, this appears to be a pretty severe season. What we don't know is if this is going to abate, or whether reporting of cases will continue."

Infectious disease experts blame this season's severity on the re-emergence of the influenza strain Type A, subtype H1N1, informally known as the swine flu. The strain first began infecting humans in 2009 and rapidly reached pandemic levels. It's been circulating every flu season since then, but this year it surged and has become the dominant strain.

The flu typically is more serious in adults age 65 and older than in younger populations. But older people appear to have some protection against H1N1, possibly from exposure to a similar strain that circulated 50 or so years ago. Younger people, though, seem to be especially vulnerable to the swine flu strain.

After the 2009 swine flu epidemic, California began requiring counties to report all flu deaths in people under age 65 to the state as one of several measures to improve influenza monitoring. The state also collects data on flu-related hospitalizations.

Bay Area hospitals in the past couple of weeks have seen a notable uptick in flu-like illnesses, in both patients in emergency rooms and inpatient wards. So far, it's tough to say just how much more severe this season is than previous years, said Karen Anderson, manager for infection control and prevention at California Pacific Medical Center.

"We certainly have had a very steep spike in January," Anderson said. "But we're not overwhelmed. We're doing OK. We're just hoping that the peak comes soon."

Anderson and other infectious disease experts said people should still get vaccinated if they haven't already. The vaccine takes about two weeks to reach full strength, but people can get some protection within a week of getting immunized.

Otherwise, people should wash their hands frequently and avoid being near those who are obviously ill. People who are sick should stay home.

"I have a little thing of hand sanitizer I carry with me," said Dr. Steve O'Brien, chief medical officer at Alta Bates Summit Medical Center. "Especially if you're on public transit, or in a public area, just give yourself a little wash-down with that."