WASHINGTON (AP) – Influenza is on the rise across the United States, driven by a new strain of the virus – and cases are expected to continue to grow with holiday travel.
That variant, known as “subclade K,” led to early outbreaks in the United Kingdom, Japan and Canada. In the United States, influenza typically begins its winter march in December. On Tuesday, the Centers for Disease Control and Prevention reported high or very high levels of disease in more than half of the states.
The CDC estimates there have been at least 7.5 million illnesses, 81,000 hospitalizations and 3,100 deaths from the flu so far this season. This includes at least eight child deaths – and is based on data from December 20, before major holiday gatherings.
Some states are particularly affected. The New York health department said the week ending Dec. 20 marked the most flu cases the state had recorded in a single week since 2004: 71,000.
It’s too early to know if this flu season will be as severe as last winter’s.
But it’s not too late to get a flu shot, which health experts say can still prevent severe illness even if someone is infected. While this year’s vaccine is not a perfect match for the subclade K strain, a preliminary analysis from the UK found it offered at least partial protection, reducing people’s risk of hospitalization.
According to the CDC, only about 42% of adults and children have gotten a flu shot so far this year.
What is the influence of subclade K?
The flu virus is a shape-shifter, constantly changing, and comes in many forms. There are two subtypes of Type A influenza, and subclade K is a mutated version of one of them, named H3N2. That H3N2 strain is always harsh, especially for older adults.
Subclade K mutations are not enough of a change to be considered an entirely new type of influenza.
But they are different enough to evade some of the protection from this year’s vaccine, said Andrew Pekosz, a virus expert at the Johns Hopkins Bloomberg School of Public Health.
Will subclade K make people sick?
The CDC said it’s too early to know how severe this season will be.
Flu seasons dominated by either version of H3N2 tend to be bad, with more infections overall and more people getting seriously ill. But Pekosz of Hopkins warned that it will take time to mitigate whether this version of subclade K simply spreads more easily or is also more dangerous.
That question aside, the CDC notes that there are some prescription drugs to treat the flu — generally recommended for people at high risk of complications. But they usually need to be started a day or two after symptoms start.
Who needs a flu vaccine?
The CDC and all major medical societies recommend a flu vaccine for almost everyone 6 months of age and older. Despite much recent misinformation and confusion about vaccines, flu recommendations have not changed.
The flu is particularly dangerous for people 65 and older, pregnant women, young children and people of all ages who have chronic health problems, including asthma, diabetes, heart disease and weak immune systems.
The vaccines are designed to protect against three strains of influenza. Despite concerns about that new H3N2 variant, they appear to be a good match against the H1N1 and Type B flu that may also be circulating this year, Pekosz said.
There are shots for all ages, as well as the FluMist nasal spray for ages 2 to 49. For the first time this year, some people may be eligible to inoculate themselves with FluMist at home.
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