Here’s why Michigan’s COVID-19 fatality rate has fallen — for now

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Michigan was reporting a grim COVID-19 fatality rate early on in the pandemic. It reached nearly 10% — which was, at one point, the highest rate in the country.

After months of slow, steady decline, it’s now at 5.8%, according to the state coronavirus dashboard. By comparison, the U.S. fatality rate is about 3%, according to a Johns Hopkins University COVID-19 mortality analysis.

But what caused that decline? 

Well, it could be a multitude of factors, infectious disease experts say. For one thing, the state is now conducting significantly more testing, which can detect new but non-fatal cases and weigh them against fatal ones. For another, demographics affected by COVID-19 have shifted, and a portion of those who got infected as the summer went by were younger people who may not be as highly susceptible to the damage the virus does. 

Michigan COVID-19 tests in April and May | DHHS

“There’s a couple different things. One is because we’ve been able to ramp up our testing,” said Sarah Lyon-Callo, state epidemiologist for the Michigan Department of Health and Human Services (DHHS). “We feel more confident we’re identifying more of the cases than we were in June.”

Michigan has conducted more than 3.2 million COVID-19 diagnostic tests in the last six months. Testing rates significantly grew in July and August. Earlier this month, Gov. Gretchen Whitmer said that Michigan ranked fifth in the nation in daily testing.

But early on in the pandemic, limitations on testing meant doctors typically only swabbed the sickest patients. The fatality rate may have looked worse because of that, according to Dr. Sandro Cinti, a professor of infectious diseases at the University of Michigan and the Ann Arbor VA Medical Center.

Michigan COVID-19 tests, June-September | DHHS

But improvements in contract tracing allowed experts to more efficiently track different types of cases and case severity, Cinti said.

“The contact tracing that was being done subsequent to those initial cases eventually picked up people who were asymptomatic and people who we would call ‘presymptomatic,’ or had very little symptoms,” Cinti said.

Lyon-Callo and Cinti also attributed the decline to another factor: younger patients.

“The cases have trended younger this summer, which I think is also affecting the fatality rate,” Lyon-Callo said.

COVID-19 began circulating more frequently through people ages 18 to 40 over the summer. For example, the median and mean age for COVID-19 cases was about 21 in a more than 180-person June outbreak at a brewpub in East Lansing. However, no deaths are linked to that.

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Michigan colleges and universities are now also grappling with even more significant COVID-19 outbreaks because students are back on campuses. This week, students at both Grand Valley State University and Michigan State University were ordered to self-quarantine for 14 days due to surges in cases.

More than 1,630 cases are spread across 32 college campuses in Michigan, according to data tracking from the New York Times. 

The college-aged population is less susceptible to severe infections that result in hospitalizations, negative long-term health effects or death, Cinti said. Fewer hospitalizations and fewer subsequent deaths among them can explain the decline in the fatality rate.

A little more than 3,200 Michigan residents died of COVID-19 during the month of April, according to the DHHS Division for Vital Records and Health Statistics. In August, the death count was significantly lower — 123 residents died of the disease. 

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In contrast, Michigan reported 252 residents died of flu or pneumonia in April and 66 died of the same infections in August. 

More than 113,000 COVID-19 cases and 6,600 deaths have been reported statewide since the disease was detected in Michigan in March.

Could another wave of COVID-19 cases in the fall and winter months lead to a jump in deaths? 

That’s a “big question mark” because it remains uncertain how a fall surge will affect older residents and those who are immunocompromised or have underlying health issues, Cinti said. For instance, multiple outbreaks and clusters are also occurring in long-term care units, like at adult day cares or assisted living facilities. That’s one reason why Whitmer and health experts have been urging Michiganders to get flu shots.

Whitmer’s decisions to issue health and safety mandates like the stay-home order as suggested by medical experts helped lower rates in Michigan, he said. 

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“The mitigation strategy — wearing a mask, social distancing, the very slow opening of businesses — has probably been key to keeping the cases down, and that will keep the mortality rate down [in the fall],” he said.

Cinti said social distancing and mask-wearing mandates are crucial until a viable vaccine is found. 

“It’s important to listen to the governor and our public health folks, and we happen to be one of the states where our governor is very much paying attention to the public health indicators and the public health expertise that we have,” Cinti said.