CDC investigating flu outbreak on UM Ann Arbor campus

Ann Arbor — Federal health officials were on campus at the University of Michigan in Ann Arbor Monday to investigate a large and sudden increase in cases of influenza among students. 

Investigators from the federal Centers for Disease Control and Prevention, the university, and state and county health departments said they hope to learn more about how the flu is spreading, and whether this year's flu vaccine is working as the nation heads into the flu season.

There have been 528 cases of influenza diagnosed at the University Health Service since Oct. 6, according to a university press release, with about 77% of the cases occurring in unvaccinated individuals.

University health officials said there's been a steep increase in cases in recent weeks, with 313 cases diagnosed the week of Nov. 8, compared with 198 cases the week of Nov. 1. The positivity rate, or percentage of tests that were positive, increased to 37% the week of Nov. 8, from 27% the previous week.

"We are seeing a lot of cases — we've had over 500 cases and over 300 of those cases were just last week," said  Emily Martin, a UM associate professor of epidemiology at the School of Public Health and one of the lead researchers to study the flu outbreak. 

The cases occurring on campus have generally been of mild to moderate severity, she added. 

"We're doing a heck of a lot more testing than we were in the past because people have been so great about coming into test when they have symptoms, because of COVID concerns," Martin said. "We're looking a lot harder than we have in the past, so that could explain some of this.

"But I would definitely say this is larger than what we've seen in the past at this time of year." 

The Department of Epidemiology has been working with the CDC for about a decade to study the effectiveness of each year's flu vaccine in the community, Martin noted.

The CDC team will be evaluating flu vaccine uptake and vaccine effectiveness and risk factors for spread through data analysis, questionnaires and the collection of respiratory specimens or serology of patients by the University Health Service. 

The flu vaccination rate is down in Michigan and across the country compared with previous years, Martin said.  But enough have been vaccinated to compare people who are vaccinated with those who aren't vaccinated to determine the efficacy of this year's vaccine, she said. 

The CDC and UM Department of Epidemiology will be investigating the outbreak on campus in collaboration with the Washtenaw County Health Department and the Michigan Department of Health and Human Services, according to a university press release. 

The state health department wasn't able to say how many flu cases have occurred in Michigan so far this year because reporting of flu cases is not mandatory in Michigan. 

"Through prompt detection and collaboration with county and state health officials, as well as School of Public Health and Michigan Medicine researchers, we quickly identified these cases as influenza A(H3N2) virus infections," said Lindsey Mortenson, medical director of the University Health Services. 

"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."

Health officials noted that the increase in cases is occurring as thousands of UM students prepare to leave for the Thanksgiving holiday, with many headed for destinations across the country and the globe. 

The officials also called on the entire community to get vaccinated against influenza as soon as possible to protect themselves and other against the flu, and keep it from spreading to infants, the elderly and others vulnerable to serious illness. 

"While we often start to see some flu activity now, the size of this outbreak is unusual," said Juan Luis Marquez, medical director at the Washtenaw County Health Department.

"We're grateful for the additional support of the CDC and our ongoing partnership with the university as we look more closely at the situation."

kbouffard@detroitnews.com

Twitter: @kbouffardDN