Pesky virus strain could mean an extra-nasty flu season
Flu season this winter threatens to be earlier and deadlier than last year, menacing youngsters and the elderly with a nasty bug that could outsmart flu shots, public health authorities warned Thursday.
They said a widespread strain that’s covered in the annual vaccine appears to have mutated in nearly half of recent flu cases confirmed by the Centers for Disease Control and Prevention.
That means the current vaccine formula may be less effective than hoped in curbing so-called H3N2 strains, which account for about 90 percent of CDC-recorded flu illnesses since late summer, said the agency director, Dr. Thomas Frieden. He said the virus is gaining momentum in clusters across the country.
“In situations such as this, we continue to recommend vaccination. Although it is far from perfect, it still offers the best chance for prevention,” Frieden said in a conference call.
Frieden recommended that people in the high-risk groups for flu complications visit their doctors quickly and ask about anti-viral treatments such as Tamiflu if they develop flu symptoms. H3N2 viruses can be especially hazardous for those groups, which include children younger than 2, adults older than 65 and pregnant women, said Dr. Amesh Adalja, an infectious disease physician at the UPMC Center for Health Security.
“When you have a mismatch with the vaccine, people are going to get infected. It’s going to be much more important to make sure people are getting anti-viral therapy,” Adalja said.
Confirmed flu cases in Pennsylvania began to surge in late November, with 677 cases reported from late September through Nov. 29, according to the state Department of Health.
Just more than 100 of those were in Allegheny County, about double the number in the area at the same time in 2013, said the county health director, Dr. Karen Hacker. She said the early trend appears similar to 2012-13 flu season, which had more than 44,000 reported cases statewide by late April and ranked among the worst in recent memory.
Two hundred people in Pennsylvania died from flu-related complications from October to April that season.
“The good news is that we’re able to monitor this pretty closely, so we’re able to see when changes are happening,” Hacker said. She said local officials knew of no flu-related deaths in Allegheny County this season, but a state briefing lists two fatalities in the commonwealth since late September.
Both involved elderly patients in unidentified counties. Only a fraction of flu illnesses end up as laboratory-confirmed cases in official state statistics, and as many as 20 percent of residents contract the virus each year, the CDC estimates.
“You better get that flu shot,” said Dr. David A. Nace, chief of medical affairs for UPMC Senior Communities. He said doctors won’t know until about February the success rate of the vaccine, which the CDC reported was 50 percent to 55 percent effective last year.
That means about half the people who got a flu shot were protected against any flu strains they encountered.
Although doctors said the shot could prove less effective this season, they emphasized the shots remain useful in about half the known cases that involve H3N2 strains, as well as illnesses caused by H1N1 viruses and two so-called B strains. The shot still might guard against mutated H3N2 strains — just to a lesser degree, they said.
Adalja said it’s still soon to know which strain will become dominant. Flu season usually peaks between December and February.
“Right now, I think it’s too early to make any definitive statements on how this season will go,” Adalja said.
Adam Smeltz is a Trib Total Media staff writer. He can be reached at 412-380-5676 or [email protected].