A Massive University of Michigan Flu Outbreak Has Prompted a CDC Investigation

A massive flu outbreak at the University of Michigan has caught the attention of public health officials at the Centers for Disease Control and Prevention (CDC). The CDC sent investigators to the Ann Arbor campus this week to learn about the dynamics of the outbreak as the U.S. enters its second flu season in the COVID-19 pandemic era. 

The first positive test was on October 6, according to the college’s newspaper The University Record. Since then, 528 cases have been diagnosed by the University Health Service (UHS) on campus, with a large upswing over the past two weeks. During the week of November 1, UHS diagnosed 198 new cases, with 27% of all tests performed coming back positive. The week of November 8, there were 313 new cases, and the positive test rate increased to 37%. 

It’s normal for cases of the flu to start going up as early as October—with flu activity typically peaking between December and February, per the CDC—but an outbreak of this size so early in flu season is concerning. “While we often start to see some flu activity now, the size of this outbreak is unusual,” Juan Luis Marquez, M.D., M.P.H., medical director of the Washtenaw County Health Department (WCHD), told The University Record. Experts worry about what it could indicate more broadly for the upcoming flu season. “This outbreak doesn’t necessarily have an immediate impact on the broader local community, but it does raise concerns about what the flu season may bring,” Dr. Marquez explained. 

While the investigation—conducted by a team of experts from the CDC, university, and state and county health departments—is only just getting underway, so far it appears that low flu vaccination rates may be one factor. According to the UHS, 77% of the diagnosed cases occurred in individuals who did not get flu shots. (While the COVID-19 vaccine is mandated for University of Michigan students, faculty, and staff, there is no flu shot requirement.) Officials are strongly recommending that students and the surrounding community get their seasonal flu shots as soon as possible.

Although the seasonal flu shot is not perfect and efficacy varies year to year, the seasonal flu vaccine generally provides significant protection against severe sickness and reduces community spread, as SELF has explained. The flu shot given in the U.S. is reformulated every flu season based on what experts predict will be the most commonly circulating strains of the constantly evolving virus. The strain behind the Michigan outbreak is a subtype of the influenza A virus called H3N2, The University Record reports, and this year, the flu shot includes inoculation against an H3N2-like virus, according to the CDC. 

Many questions still remain, and investigators are hoping that the insights they glean from studying this flu outbreak might be helpful for getting ahead of this flu season across the U.S. “Partnering with the CDC will accelerate our understanding of how this flu season may unfold regionally and nationally in the setting of the COVID-19 pandemic,” Lindsey Mortenson, M.D., UHS medical director and acting executive director, told The University Record. For instance, the team is aiming to learn about the efficacy of the current flu vaccine and risk factors for flu transmission (among other things) through a combination of data analysis, surveys, and lab analysis of patient samples, according to The University Record

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