Mutated H1N1 Drives Flu Growth in 44 States as Positivity Hits 5.7%
Updated
Updated · TODAY · Oct 26
Mutated H1N1 Drives Flu Growth in 44 States as Positivity Hits 5.7%
3 articles · Updated · TODAY · Oct 26
Summary
CDC estimates show flu infections are growing or likely growing in 44 states, with Louisiana and Hawaii already at moderate activity and cases rising unusually early since August.
H1N1 is driving most U.S. cases, and experts say a new G155E mutation may help the virus evade existing immunity, leaving even people infected last season more vulnerable.
The early surge is showing up in surveillance data: 5.7% of flu tests were positive in the week ended Oct. 17, versus less than 1% a year earlier, while outpatient flu-like illness visits reached 2.2%.
Hospitalizations and deaths are also rising, though experts say it is still too early to judge whether the 2026-2027 season will be more severe overall.
Doctors are urging vaccination before the end of October, saying the updated 2026-2027 shots should still reduce severe illness even if the circulating H1N1 strain is not a perfect match.