As an infectious disease specialist for the better part of four decades, Bernhard “Bud’’ Wiedermann has deep expertise on a range of illnesses, from malaria to Lyme disease to recurrent fevers.
This year’s flu season has thrown him a curveball, though it is thankfully one he can adjust to: A predominant influenza B virus for the first time in 27 years.
When outbreaks of the flu began earlier than usual in the fall, Wiedermann and his colleagues at Children’s National Hospital in Washington, D.C., noticed a leading cause was a virus that doesn’t typically emerge until the end of the season and is more likely to affect kids.
“All of us here when we started seeing that coming through, not only from the CDC data but from our own testing, we were like, ‘Wow, what’s going on? This is very strange,’’’ Wiedermann said.
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Though initial signs pointed to the powerful A(H3N2) strain as the biggest concern this season, the Centers for Disease Control and Prevention said most of the illnesses have been caused by B/Victoria viruses, followed by A(H1N1) viruses.
The impact has been particularly harsh in Louisiana, where a New Orleans pediatric care facility reported 1,268 confirmed B virus infections in children from July 31 to Nov. 21, leading to 23 hospitalizations.
Nationwide, the CDC said flu activity is high and will remain that way for weeks, although the level of severity appears lesser than in the past. For the season, the agency has tallied at least 9.7 million cases of the flu, 87,000 hospitalizations and 4,800 deaths.
More than 68% of the positive results from tests in clinical labs were linked to the influenza B virus, which had not been predominant since the 1992-93 season. Those infections have accounted for nearly half the hospitalizations reported to the CDC.
“I think there is a common misconception that influenza B viruses are associated with milder disease than flu A viruses,’’ CDC spokeswoman Kristen Nordlund said. “Influenza B viruses can cause severe illness in people of all ages, including children and adults.’’
The symptoms are the same regardless of the virus: fever in many cases, as well as a sore throat, cough, body aches, fatigue, runny or stuffy nose and headaches. But one significant difference is this year’s dominant viruses figure to impact children and young adults more than older folks.
That makes it imperative for parents to make sure their kids get a flu shot, even at this point in the season, the CDC said. In past years, about 75% of the children who died from the flu weren’t fully vaccinated.
Nordlund said data showing the effectiveness of this season’s vaccine at fighting off the prevalent viruses won’t be available until late February, and preliminary indications are mixed, but she reiterated that some protection is better than none. In addition, studies have shown the effects of contracting the flu are less severe on those who are vaccinated than on those who aren’t.
The CDC and Wiedermann emphasize the flu shot is effective and highly recommended for pregnant women regardless of their trimester, and also for children six months and older, who can take antivirals like Oseltamivir (known by the brand name Tamiflu) and others as early treatment or prevention.
Wiedermann, who’s also a professor of pediatrics at George Washington University, worries about the vulnerability of unvaccinated children to a virus that’s typically not a major concern at this time of the season.
“If we have the combination of not being immunized and being young enough that they haven’t seen the natural influenza B virus that much, that means we have whole lot of kids out there who aren’t immune to this virus,’’ Wiedermann said, “so we expect a lot of them to get infected.’’