Flu rising across the U.S. as CDC tracks subclade K H3N2 variant

Flu cases are rising rapidly across the United States as the CDC tracks a new variant of the virus, known as “subclade K,” the Associated Press reported.

The AP said the CDC reported high or very high levels of illness in more than half the states as of Tuesday, with expectations that cases will continue to grow as holiday travel increases contact.

The CDC estimated that, so far this season, there have been at least 7.5 million illnesses, 81,000 hospitalizations and 3,100 deaths, based on data as of Dec. 20, before major holiday gatherings. The estimate includes at least eight child deaths, the AP reported.

Some states have seen especially large spikes. New York’s health department said the week ending Dec. 20 marked the most flu cases the state had recorded in a single week since 2004, with 71,000 cases, the AP reported.

The AP said it is too soon to know whether this flu season will match the severity of last winter. The CDC also said it is too early to determine how severe the season will be, even as flu seasons dominated by H3N2 variants “tend to be bad,” with more infections and more serious illness.

The CDC and public health experts point to the virus’s ongoing evolution. The AP described flu as a shape-shifter that constantly mutates, with subclade K identified as a mutated version of H3N2, a subtype within Type A flu. The AP reported that subclade K’s mutations are not enough to be considered an entirely new kind of flu, but they are different enough to evade some protection from this year’s vaccine, according to Andrew Pekosz, a virus expert at Johns Hopkins Bloomberg School of Public Health.

Pekosz cautioned that it will take time to understand whether the subclade K version mainly spreads more easily or is also more dangerous, the AP reported. The CDC noted that prescription medicines can treat flu, usually recommended for people at high risk of complications, and that the medications generally need to be started a day or two after symptoms begin.

Even with uncertainty about how the season will unfold, the AP said it is not too late to get a flu shot. Health experts told AP the vaccine can still prevent severe illness even if someone gets infected, and a preliminary analysis from the United Kingdom found at least partial protection against the subclade K strain by lowering the risk of hospitalization, the AP reported.

The AP said the CDC and major medical societies recommend flu vaccination for just about everyone age 6 months and older, and that flu is particularly dangerous for people 65 and older, pregnant women, young children, and people of any age with chronic health problems such as asthma, diabetes, heart disease and weak immune systems. The vaccines are designed to protect against three influenza strains, and Pekosz said the vaccines appear to be a good match against H1N1 and Type B flu that may also circulate this year.

According to the CDC, only about 42% of adults and children have gotten a flu vaccination so far this year, the AP reported. The AP said flu shots are available for all ages, and that FluMist nasal spray is for ages 2 to 49. It added that, for the first time this year, some people may be eligible to vaccinate themselves with FluMist at home.