Indiana Battles 'Super Flu' Surge: Marion County Sees 37% Spike in ER Visits

Indiana is in the grip of a severe flu outbreak driven by subclade K, a highly transmissible variant of H3N2 that accounts for approximately 90 percent of cases statewide. The Indiana Department of Health has declared flu activity "very high" across the state, placing Indiana among 30 states experiencing the same alert level. Nationally, the surge is staggering: more than 7 million people have contracted the flu since October, with 3,100 deaths reported. In Indiana alone, 17 flu-related deaths have been documented this season, with 12 of those occurring in people older than 65.

Marion County has become the epicenter of the outbreak in Indiana. Emergency room visits for flu symptoms surged 37 percent in the week before late December compared to the previous week, with 7 percent of all ER visits tied to flu-related illnesses. Among children ages 5 to 17, the increase was even steeper at 28 percent. The severity of the outbreak prompted major health systems—Indiana University Health, Ascension St. Vincent, and Franciscan Health—to implement visitor restrictions at their facilities to contain spread.

Dr. Tom Hrisomalos, an infection disease specialist with Indiana University Health, attributes the exceptional severity to the subclade K strain's evolution. "It has mutated over the last few years, and with that mutation, it has become more transmissible," Hrisomalos said. He noted that emergency department visits, urgent care appointments, and primary care office visits have spiked in recent weeks, though he characterized hospitalization increases as within normal range for severe flu seasons. Health officials say vaccination remains available and could still blunt the current spike, which is expected to last several weeks.

The outbreak coincides with a broader wave of respiratory illnesses sweeping the nation. In addition to the flu surge, norovirus, COVID-19, and whooping cough cases are rising nationwide, compounding pressure on Indiana's healthcare system. To protect themselves and others, state health officials recommend residents wash their hands frequently, cover coughs, and wear masks in crowded settings—particularly in schools and public spaces where transmission is easiest.