Health officials in Illinois are warning of a new and unexpected mutation that could make for a “more serious flu season” as cases are already on the rise.
The new variant, known as “Subclade K,” is part of the H3N2 parent group, or a type of Flu A.
“This mutation has been associated with an increased rate of flu infections in countries that are already witnessing it and also in parts of the United States,” said Illinois Department of Public Health Chief Medical Officer Dr. Arti Barnes.
The new strain’s impact on other countries like Japan and in the UK has left some local doctors “on guard.”
“This strain is spreading fast, it’s spreading widely and so we really are on guard right now and are bracing ourselves for another flu season,” Barnes said.
Doctors have warned that the new strain will likely lead to an increase in flu cases this winter.
“Because it’s a strain that we haven’t seen and because less people are vaccinated, we will likely be seeing more influenza this year than possibly in a typical year,” said Dr. Sharon Welbel, chair of the division of infectious disease and hospital epidemiology for Cook County Health.
Welbel noted that having a severe flu season this winter would mark a rare occurrence.
“Last year, we also had a severe influenza season. We don’t often see severe influenza seasons back to back, but that doesn’t mean that we can’t,” she said. “And we already know that in places like Japan, they did experience a severe season. So by having this new strain that is not specifically targeted in our vaccine, we could be seeing a severe season this year.”
Barnes agreed, saying that while predictions from the Centers for Disease Control and Prevention earlier called for a milder flu season, that is no longer the case.
“The original prediction by CDC was that this year we would have a milder flu season because we did have a more serious flu season [last year] and in some ways people have paid their immune debt, so to speak,” she told NBC Chicago. “But what was not anticipated was after the vaccine’s strains were determined and after these predictions were made that this strain started to take off in Europe. And we were not anticipating that the amount of mutations on this would make the transmission more widespread than we were expecting.”
While Illinois’ flu levels remain relatively low, they are rising, according to IDPH, though it’s not yet clear if a surge is on its way. Experts said some cases of the strain may have already been detected in Illinois.
“Illinois specifically still has very low flu rates, but we are seeing a rise. Whether this rise is disproportionate to what we would expect for this time of the year is too early to tell,” Barnes said. “We’re not seeing enough numbers to call it in terms of whether this is a severe flu season for Illinois yet. However, the few samples of flu that we do have are pointing to the fact that it’s in the same parent group or the parent strain, the H3 strain that is part of this Subclade K type of flu strain.”
Are vaccines effective against the new strain?
Doctors said current vaccines are expected to offer protection against serious illness, particularly when it comes to children.
“Because we didn’t know about [this mutation] before the influenza vaccine was created for this season, that variant is not in our flu vaccine this year. So it does make that vaccine likely to be less effective, but not ineffective,” Welbel said, adding that “the one thing that would make a difference based on what we’re seeing in the UK is if we have a population that’s well vaccinated and also practicing good respiratory hygiene around others to prevent the spread to those who are most vulnerable.”
Barnes stressed that the vaccine was formulated to offer protection against H3N2, which is reassuring, though she noted the new strain is still believed to be more contagious.
“This strain is supposed to be more associated with severe flu season, very rapid spread of the infection. So we think it is very likely more transmissible or more infectious. We don’t know yet if it’s more severe,” she said. “We are looking very closely at countries that are experiencing it like the UK, that have started experiencing it since August, and what we have also discovered through that is that thankfully the vaccine that is in play is still effective towards preventing severe hospitalizations and ER visits from the strain too … it’s about as effective as most flu vaccine strains each season. It is far more effective in children, and children under 8 are a very vulnerable group for complications from flu.”
Experts stressed that getting vaccinated before the new strain takes hold in the U.S. can help.
“Everybody should get vaccinated. It’s definitely not too late to get vaccinated. And it won’t be too late until we really start seeing influenza numbers coming down,” Welbel said.
Flu vaccines are available in the U.S. for anyone 6 months and older.
Symptoms to watch for
Health experts said there are no unique symptoms to watch for when it comes to Subclade K.
“It is pretty much the same as the other flu symptoms, which really grounds itself in fever, cough, cold, body aches, and chills,” Barnes said. “And so we really want to warn people that you might not have any unique symptoms that point to this specific strain, unlike say COVID or RSV or any other respiratory infections, but what is important to know is that once you do start feeling ill, that you do take precautions to make sure you don’t spread it.”
Welbel said cases of this flu strain are likely to be more severe than the common cold.
“Generally, there will be fever, muscle aches, there can be other symptoms such as gastrointestinal symptoms, but people feel pretty sick as opposed to having what we would call the common cold,” she said.
According to Welbel, H3N2 is a type of flu that often causes more serious cases.
“In general … people with H3N2 do get sicker than people with H1N1 or influenza B,” she said.
She stressed that people are most contagious within the first two days of symptoms, but can remain contagious for up to five days.
The CDC reports the following symptoms for those with flu:
fever* or feeling feverish/chills
cough
sore throat
runny or stuffy nose
muscle or body aches
headaches
fatigue (tiredness)
some people may have vomiting and diarrhea, though this is more common in children than adults.
*It’s important to note that not everyone with flu will have a fever.
According to Barnes, medications that fight against current flu strains are expected to work for this strain.
“We believe that they should work just as well and so it’s important to remember that if you do have flu, you have about 48 hours to get on antivirals,” she said. “And that would be the most effective time to get on treatment. So I would strongly encourage people to make sure they know what they’re dealing with when they start to get sick, start to experience those fevers and chills and cold. Sometimes you can also have upset stomach diarrhea associated with flu.”
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