New Flu Mutation Causes Severe Illness: See Latest VA Data

Close gatherings over the Thanksgiving holiday could cause an uptick in emergency room visits in Virginia 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.

Virginia 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.

“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.

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

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. 20, shows that acute respiratory illness rates overall are low in Virginia, with 29 cases reported.

For the week ending Nov. 15, the Virginia Department of Health reported that COVID-19 was diagnosed in O.35 percent of emergency room visits, which was slight up from 0.30 percent during the previous. These were considerably lower numbers than the 1.73 percent reported for the week ending Aug. 30, which was the state's highest percentage of diagnosed cases for 2025.

Virginia also saw similarly low percentages of diagnosed influenza and RSV cases reported at emergency departments for the week ending Nov. 15, according to the health department. The 0.16 percent of diagnosed influenza cases was slightly up from the previous week, which was 0.15 percent.

By comparison, the percentage of diagnosed RSV cases reported by emergency departments in Virginia for the week ending Nov. 15 took a jump over the previous week, going from 0.09 percent to 0.16 percent. The number of RSV cases on Nov. 15 was highest percentage reported since the week ending March 1, which was also 0.16, according to the health department's data.

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 29 monitoring sites will provide a clearer picture of COVID, flu and RSV rates in Virginia when the data is updated Friday.

On Nov. 15, the overall respiratory illness activity in Virginia was low and stable, according to the health department. COVID-19 and RSV levels were stable, reporting 0.3 percent and 0.2 percent of all emergency department diagnoses, respectively. However, the number of diagnosed influenza cases was trending upward, acounting for 0.5 percent of all emergency department visits.