North Texas Flu Surge: Subclade K Strain Spikes Cases as Vaccine May Only Partially Protect

A fast‑moving flu strain, subclade K, is raising alarms in North Texas as holiday travel ramps up.

What Is Subclade K?

Subclade K is a mutation of the influenza A(H3N2) virus and is now the dominant strain in circulation nationwide, according to recent CDC data. The strain was identified only in August, months after vaccine development, which means the current flu shot may not be an ideal match.

Impact on North Texas

Dr. Joseph Chang, chief medical officer at Parkland Hospital in Dallas, said flu numbers there are already higher than at this point last season. “Our numbers here at Parkland, in particular, are definitely higher than they were last year,” Chang said.

Dallas County Health and Human Services reports that local flu activity remains relatively low compared to some parts of the country, but has increased steadily in the past two weeks. Vaccination rates in North Texas are also trailing previous years, according to Chang. He says lower community protection increases the chance of infection.

Vaccine Effectiveness

The CDC says this year’s flu shot was designed to protect against three main virus strains, including H3N2. Because subclade K was identified after the vaccine was formulated, experts say it may not be an ideal match. “Our flu vaccine was designed against H3N2, but a cousin, a new cousin has formed itself against H3N2, and so it’s covered partially,” Chang said.

While the vaccine may not fully prevent illness from this strain, health experts say it still helps reduce the severity of symptoms and the risk of hospitalization. “People are going to get sick because they’re going to get full‑blown flu,” Chang said.

Herd Immunity and Recommendations

Herd immunity takes 75 to 80 percent. Since we’re at about 40 to 50 percent, we’re not there,” he said. “So you’re not protected by the people around you.”

Chang recommends people get vaccinated as soon as possible, especially with Christmas gatherings approaching. “Even partial taking effect is better than zero,” he said. “So don’t be like, ‘Oh, I give up, it’s too late.’ No, absolutely, go get it. Rush there today if you have to.”

CDC Guidance

The CDC continues to recommend flu vaccination for everyone 6 months and older during the flu season, especially with new strains spreading.

Key Takeaways

• Subclade K, a mutation of influenza A(H3N2), dominates nationwide flu cases.
• Parkland Hospital reports higher flu numbers than last season, and local activity has risen steadily.
• The current flu shot may only partially protect against subclade K, but can still reduce severity.

The situation underscores the importance of vaccination and the challenges posed by rapidly evolving flu strains. Stay informed, get vaccinated, and take precautions to protect yourself and your community.