Flu begins to spread across Northern California

Flu season is ramping up across the North Coast, which is seeing a particularly virulent strain that already has become widespread in other parts of the country.

The influenza virus has been detected in 10 percent of Kaiser Permanente patients with flu-like symptoms who have been tested in Northern California, up from 4 percent just two weeks ago, said Dr. Gary Green, chief of infectious disease at Kaiser Permanente Medical Center in Santa Rosa.

The spread of the flu virus will likely accelerate after the holiday break, when adults return to work and kids go back to school after spending time in close quarters. It typically peaks between January and March.

“Clearly, domestic travel during the holidays increases the spread of influenza,” Green said.

Flu activity is much worse in other regions of the United States, particularly the Southeast, Midwest and parts of the Northeast, where about 26 percent of patients with flu-like illness are testing positive for the influenza virus, Green said.

Early data suggest the current flu season could be severe. The predominant flu this year, 96 percent, is Type A. Of that, 99.9 percent is made up of the H3N2 subtype, which has a history of causing widespread illnesses and deaths, according to the Centers for Disease Control and Prevention.

Making matters worse, roughly half of the H3N2 viruses analyzed are so-called “drift variants” - viruses with antigenic or genetic changes that make them different from the vaccine distributed to fight the flu this year, the CDC warned this month. As a result, the vaccine’s ability to protect against those viruses may be reduced, although vaccinated people may have a milder illness if they do become infected.

“The vaccine may not be as protective as they hoped for,” said Fred Drach, infectious disease consultant for Annadel Medical Group in Santa Rosa.

Depending on the formulation, flu vaccines protect against three or four different flu viruses. Even during a season when the vaccine is only partially protective against one flu virus, it can shield against the others. For example, during the 2007-2008 flu season, the predominant H3N2 virus was a drift variant yet the vaccine had an overall efficacy of 37 percent and 42 percent against H3N2 viruses.

“While the vaccine’s ability to protect against drifted H3N2 viruses this season may be reduced, we are still strongly recommending vaccination,” Dr. Joseph Bresee, chief of the CDC’s Influenza Epidemiology and Prevention Branch, said in a statement. “Vaccination has been found to provide some protection against drifted viruses in past seasons. Also, vaccination will offer protection against other flu viruses that may become more common later in the season.”

Influenza viruses are unpredictable and constantly changing. A committee of experts must pick which viruses to include in the vaccine many months in advance in order for the vaccine to be produced and delivered in time for the upcoming flu season. There is always the possibility that viruses will drift during that time.

Viruses that live only in one species are easier to contain, but Influenza A virus can live and replicate in humans, pigs, horses, birds and several other species, Green said.

“So you can’t really contain it,” he said.

Green and Drach both urged local residents to get the flu vaccine, despite its lower efficacy this year. Those who are at high risk of flu-related illness include hospitalized patients, children younger than 2 and adults older than 64.

Other high-risk groups include pregnant women and new mothers who are less than two weeks postpartum, as well as people with underlying chronic conditions such as diabetes, lung disease and kidney disease.

Officials also recommended taking the following steps to guard against the spread of flu:

Wash your hands often with soap and water, especially after you cough or sneeze. Hand sanitizers also are effective.

Cover your nose and mouth with a tissue when you cough or sneeze, and dispose of the tissue.

Avoid spreading germs by not touching your eyes, nose or mouth. Avoid close contact with anyone who is sick.

If sick, stay home at least 24 hours after being free of fever or signs of a fever without the use of fever-reducing medications.

You can reach Staff Writer Martin Espinoza at 521-5213 ?or martin.espinoza@press?democrat.com. On Twitter ?@renofish.