Health & Medicine

New version of 2009 pandemic flu virus surges; targets healthy middle-aged people and young adults

Just days after a Christmas Eve federal health advisory, Sacramento County’s top public health official warned Friday of a sudden increase in local influenza activity, possibly led by a strong resurgence of a version of the virus behind the 2009 worldwide flu pandemic.

Olivia Kasirye, the county’s public health officer, said the viral strain known as influenza A pH1N1 is atypical because it tends to hit young people and healthy adults the hardest. In 2009, the H1N1 virus caused more illness in children and young adults, compared to older adults.

“From last week to the current one, we saw a significant increase in the percentage of positive flu tests, from 6 percent to 20 percent,” Kasirye said. “Young people and healthy middle-aged people are some of the cases we have right now. Being otherwise healthy is a risk factor for this virus.”

Kasirye said though individuals in good health may not believe they need a flu vaccine, the behavior of the pH1N1 virus – a version slightly different than the 2009 virus – presents an argument in favor of getting vaccinated. “We want people to be aware, to know that it’s out there.”

State and federal officials confirmed that the pH1N1 virus is the “predominant strain” circulating so far this season both in California and nationwide. Statewide, no influenza outbreaks have been reported to date and only local – as opposed to regional – cases have popped up, according to data collected by the state up to Dec. 14.

The Centers for Disease Control and Prevention issued an advisory Tuesday to physicians alerting them to “severe respiratory illness among young and middle-aged adults, many infected with influenza A pH1N1 virus. Multiple hospitalizations, including many requiring intensive care unit admission, and some fatalities have been reported.”

Among 1,071 known influenza cases between Oct. 1 and Dec. 21, the CDC reported, 92.6 percent were influenza A, and 97.7 percent of those were subcategory 2009 pH1N1.

“If pH1N1 virus continues to circulate widely,” the CDC warned, “illness that disproportionately affects young and middle-aged adults may occur.”

Kasirye’s information on the local percentage increase of flu cases week-to-week is based on informal data reported from three major hospital systems. Only one of the hospitals had hard numbers instead of just percentages to share – out of 867 specimens, 164 tested positive for the influenza A virus and nine tested positive for influenza B viruses also targeted by this year’s vaccine.

In November and December of this year, the Sacramento Department of Public Health learned that five people with the flu were so sick they ended up in local intensive care units, compared to one case during the same period last year. The ages of those individuals were 2, 36, 47, 53 and 56, Kasirye said. So far, no deaths have been reported.

Nationwide, the CDC estimates that each year, more than 200,000 people are hospitalized for influenza. Over a period of 30 years, flu-associated deaths have ranged from as low as 3,000 to as many as 49,000, depending on the severity of the flu season.

Sacramento County, the state and the CDC all recommend annual vaccinations for those six months and older as the best tools for prevention, although the CDC also said flu shots might not be 100 percent effective in all cases. People who show symptoms of the flu – including fever, cough, body aches and respiratory distress – should consider seeing a doctor for anti-viral medicine, the CDC said.

“If not enough people get vaccinated in a community, there is always an increased risk for influenza to reach epidemic proportions and for localized outbreaks to take place,” said Dr. Gilberto Chavez, California state epidemiologist.

Kasirye said, “A person’s decision to receive the vaccination or not impacts the entire community, as the flu vaccine not only protects the individual from illness but also those nearby.”

Flu vaccines take two weeks to become fully effective. Peak influenza activity typically occurs in late December to early February. The Sacramento County Department of Public Health recommends a flu shot once a season.

This year, there are more types of flu vaccines to choose among than ever before, as evidenced by the five options offered by Walgreens, which spokeswoman Emily Hartwig said follows CDC recommendations in stocking vaccines until the end of April. Other retail locations, such as Costco, may offer only two versions of the vaccine, and for a shorter period of time – in Costco’s case, online information indicates flu shots will not be available past Dec 31. Other local retail outlets offering flu vaccines include Target, Rite Aid, CVS Pharmacy and some independent pharmacies.

This year, for the first time, a quadrivalent flu shot is available alongside the traditional trivalent flu shot. The trivalent covers two strains of influenza A, including pH1N1, and one influenza B strain. The quadrivalent covers all those and a second influenza B strain.

For vaccination options, age restrictions (some retail outlets don’t offer flu vaccines for young children) and locations of outlets near you, go online to and type in your ZIP code.

Editor’s note: This story was changed Dec. 31 to remove a reference about the potency of the vaccine and to add information about how often to get a flu shot.

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