Close gatherings over the Thanksgiving holiday could cause an uptick in emergency room visits in Florida due to a trio of respiratory illnesses that typically rise this time of year, as well as a new mutation of the common flu that doesn’t respond to this year’s flu shot.

Florida emergency rooms typically see an increase in COVID-19, influenza and RSV rates during the holidays. This year’s flu season could be more serious due to a new Influenza H3N2 mutation known as “subclade K,” which is spreading in North America, including the United States.

Although the current flu vaccine offers protection against the H3N2 strain, it doesn’t cover subclade K, which hadn’t been identified when the vaccine was developed. The variant has mutated seven times, making H3N2 an even more serious threat, according to experts.

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“Knowing that there’s a new mutated strain out there and H3N2 generally causes more severe disease is concerning,” Dr. Robert Hopkins Jr., medical director of the National Foundation for Infectious Diseases, told NBC’s “Today” show.

The symptoms of the new strain are similar to those caused by common influenza, including fever, chills, body aches, headaches, extreme fatigue, congestion or runny nose, and coughing.

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The symptoms come on suddenly. “It’s that hit-by-a-truck feeling,” Hopkins told “Today.”

Patch has reached out to the Florida Department of Health about the latest flu mutation. This story will be updated when the agency responds.

On its website, the department urges residents to get vaccinated against the flu.

“Annual vaccination is the best way to protect yourself and others from potentially severe complications from flu. Flu shots take up to two weeks to become fully effective, so it’s important to get vaccinated as soon as possible to reduce your chances of getting the flu this season,” FDOH said.

In Florida, the flu season tends to happen a bit later in the year than other parts of the country, Dr. George Rust, director of Florida State University’s Center for Medicine and Public Health, said in a news release.

This means that just before the holiday season is the best time of year to get vaccinated.

“In Florida, our flu season will peak a little later than it does up North, but you can still think of mid-December through mid-February as the season when we’ll see the most cases,” Rust said. “It takes two weeks for the flu shot to give full protection, but that protection can wane a bit after many months.”

This particular mutation is now dominant in many countries, including Japan, the United Kingdom and Canada, Forbes reported.

The CDC currently lists Influenza A H3N2 as the cause of most flu cases in the United States. The extent of the spread of the subclade K mutation in the United States is unknown because the agency didn’t do any tracking for its FluView report during the recent government shutdown.

The latest data from the CDC, last updated on Nov. 19, shows that acute respiratory illness rates overall are very low in Florida.

The number of positive flu cases increased in most Florida counties between Nov. 9-155, according to the FDOH’s weekly Florida Flu Review.

The number of flu-related emergency department visits increased during this time, according to the report. Those most affected by the flu in Florida this year, including hospital admissions and deaths, have been 65 and older.

The predominant strain during this reporting period was Influence A H1N1, FDOH said.

Nationwide, acute respiratory illnesses remain at low or very low levels, according to the CDC; however, emergency room visits for RSV are increasing in many states in the South and Southeast. COVID-19 activity remains low, and seasonal flu activity is low nationally but increasing, according to the surveillance report.

Wastewater surveillance reports from 13 monitoring sites will provide a clearer picture of COVID, flu and RSV rates in Florida when the data is updated Friday.

On Nov. 20, data based on wastewater viral activity showed that COVID and the flu were at very low levels in Florida. Meanwhile, the viral activity level of RSV was moderate.

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