Last updateTue, 17 Oct 2017 5pm


Flu season enters full swing, particularly for the young

Flu viruses can swap ribonucleoproteins, depicted above as green squiggles, one of two ways new strains emerge from existing virus types. Health agencies track the emergence of new strains and try to update vaccines to match each year’s most common strains.

The flu has arrived, but the seasonal scourge bears some good news this year – those who got a flu shot should be protected.

“So far this year the vast majority of the flu is covered by the H1N1 vaccine,” said Dr. Charles Weiss, a physician with the Palo Alto Medical Foundation. “WHO (World Health Organization) and the CDC (Centers for Disease Control and Prevention) try to guess what’s going to be the most prevalent strain, and they’ve done a pretty good job.”

This year’s dominant strain, H1N1, caused pandemic illness in 2009. It earned the moniker “swine flu” because the respiratory virus had already been circulating in pigs. Since 2009, H1N1 has continued to crop up in humans but not necessarily as the most common flu virus. Last year, a variant, H3N2, dominated among those tested for flu. The varieties of flu surging in a given year can make a difference – not all types behave the same way.

“A lot of the damage is done by the H3N2 in seniors, and the H1N1 that we’ve had since the 2009 pandemic seems to be tougher on kids, young adults and middle-aged adults, not seniors,” Weiss explained.

The medical community hasn’t fully determined why the different strains of the virus strike different parts of the population, but seniors may be protected from H1N1 by immunity to a similar strain gained decades ago. Seniors are also more than twice as likely to get vaccinated than 18- to 49-year-olds. And young people who become seriously ill may have a vulnerability to the virus that is not yet well understood.

Local impact

As of Monday, four people had died of the H1N1 infection in Santa Clara County in this year’s outbreak, three people in their sixties and a 41-year-old woman. Medical providers have confirmed 13 cases of severe flu thus far this season that occurred in people under 65 and were serious enough to require hospitalization in an intensive-care unit.

“The scary part for a lot of people is that some of these are healthy young adults. The theme that seems to run through all of them, whether they have underlying disorders or not, is that most of them did not get vaccinated,” Weiss said. “Not being vaccinated puts you at risk. I think that the 18- to 50-year-old group thinks they don’t need it. Some years that’s closer to true, but this year it’s not true. Their old friend from 2009 is back with a vengeance.”

According to the CDC, flu activity typically peaks in the U.S. in January or February, though the season can begin as early as October and stretch as late as May.

“We started to see a trickle in mid-December, and really it’s just the last two weeks that it has picked up considerably,” Weiss said of the Bay Area.

The Public Health Department urges residents to get a flu vaccination if they haven’t already. Flu vaccine is still available at local pharmacies and is particularly recommended for people at risk of developing serious complications if they are stricken with the flu. That includes pregnant women, children younger than 5, people older than 65 and those with medical conditions such as asthma and diabetes. The Palo Alto Medical Foundation offers a preservative-free, latex-free flu vaccine to its patients.

Healthy people who do contract a flulike illness are advised to stay at home until their fever has been gone for 24 hours. Contact a physician if symptoms include shortness of breath, a fever greater than 102 F or a fever that lasts more than a few days.

The influenza virus is divided into three types, labeled A, B and C. Together, they’re responsible for the seasonal surge in flu infections. Both H1N1 and H3N2 are influenza A viruses. The H1N1 variant that emerged in 2009 (often called “2009 H1N1”) caused the first pandemic in more than 40 years. It has predominantly replaced its predecessors in circulation. This year’s quadrivalent flu vaccine protects against both types of influenza A and two types of influenza B.

For more information, visit cdc.gov/flu.

Flu prevention

Flu viruses are spread mainly through the droplets produced by coughing, sneezing or talking. According to the Centers for Disease Control and Prevention, healthy adults can spread the virus for a day before and five to seven days after becoming sick. Symptoms start one to four days after the virus enters the body.

• Cover your cough: Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.

• Wash your hands: Wash your hands often with soap and water, especially after you cough or sneeze.

• Avoid spreading germs: Avoid touching your eyes, nose and mouth. Try to refrain from close contact with anyone who is sick.

• Stay home if you are sick: If you are sick with flulike symptoms, stay home from work or school.

Source: Santa Clara County Public Health Department

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