New Flu Mutation Causes Severe Illness: See Latest CA Data

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

California 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 of common influenza, including fever, chills, body aches, headaches, extreme fatigue, congestion or a 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.

California Data

In California, Seasonal influenza activity is rising, particularly in the Bay Area and Southern California. Hospitalizations are currently low but are expected to increase. The California Department of Public Health continues to recommend influenza vaccination, testing, and timely treatment.

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 California.

“A new H3N2 flu strain (subclade K) is causing severe early flu seasons in the Northern Hemisphere. Current influenza vaccines continue to offer protection, especially against severe disease,” according to the CA Department of Public Health. “RSV activity is increasing in California, especially among children. Hospitalizations are currently low but are expected to increase. Immunizations are recommended for all eligible persons.

“COVID-19 activity remains very low statewide, with minimal test positivity, emergency room visits, and hospitalizations. CDPH continues to recommend COVID-19 vaccination, especially for those at increased risk and for all who choose protection."

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 most recent surveillance report.