CDC: Unprotected influenza strain prevalent; severe season expected
The high prevalence of a drifted influenza A(H3N2) strain could lead to a worse influenza season, CDC Director Thomas R. Frieden, MD, MPH, announced today during a media briefing.
Ninety-one percent of approximately 1,200 influenza-positive tests reported to the CDC this year were influenza A virus, and 9% were influenza B, according to Frieden. Nearly all reported influenza A virus were H3N2, about half of which were antigenically different from the corresponding component included in the 2014 vaccine. This is a result of the drifted strain first being detected in March, Frieden said, after vaccine development had already begun.
“Flu always has the potential to be serious, but H3N2 viruses tend to be associated with more severe seasons,” Frieden said during the briefing. “The rate of hospitalization and death can be twice as high or more than flu seasons where H3N2 doesn’t dominate. People with certain health conditions such as asthma, diabetes, heart disease, lung disease and pregnancy are also at high risk.”
Frieden still recommended that US citizens receive the current influenza vaccine for protection against the other included strains.
“If we have a severe season with H3N2 virus predominating, getting a vaccine — even if it doesn’t provide as good of protection as we would hope — would be more important than ever, and remains the single-most effective way to protect yourself against the flu,” Frieden said.
An influenza season without a highly effective vaccine means that antiviral medication will be especially important, he said. Treatment with antivirals can reduce illness duration and severity and is most effective when initiated within 48 hours of influenza symptoms. Despite this, prescription antivirals often are underprescribed.
“We strongly recommend that if doctors suspect the flu in someone who may be severely ill from the flu, they don’t wait for the results of a flu test before starting antivirals,” Frieden said. “Probably fewer than one in six people who are severely ill with flu get antiviral drugs. It’s very important that we do better.”
Frieden also stressed that anyone infected with influenza should take steps not to infect others. This includes staying home from work or school when sick and using other basic sanitation practices.