Safer-At-Home Measures Helped Stem Spread Of COVID-19 In Wisconsin, Research Suggests

May 18, 2020

There have been a lot of mysteries about COVID-19 since it first appeared in humans in late 2019. How does it spread? How does the coronavirus mutate? Which organs does it affect? Virologist Thomas Friedrich is one of the people tasked with answering these questions.

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Friedrich is an associate professor in the Department of Pathobiological Science at UW’s School of Veterinary Medicine who's been tracking COVID-19 in Wisconsin. His research shows that safer-at-home measures have seemingly helped stem the spread of coronavirus in Wisconsin. To understand how his research came to that conclusion, we first have to understand how viruses spread and change over time. 

"When I’m talking to you right now, I am spewing out little particles that you can’t even see — sometimes you can. Well, we all do that all the time. Some of those little particles can contain viruses, and when you stand next to somebody, you sometimes breathe in some of those little particles," says Friedrich. 

Inhaling these particles can lead to infection, which is why health officials are urging people to wear masks. Masks not only protect people wearing them from inhaling these particles, but they also cover the wearer's mouth so their own don't spread. 

"Every time the virus takes over a new cell, there's a chance for a random mutation to occur. These mutations occur somewhat predictably over time."

"Every time the virus takes over a new cell, there's a chance for a random mutation to occur. These mutations occur somewhat predictably over time," Friedrich explains. 

He continues, "Right now, we're just using them as a genetic marker to tell the difference between, let's say, viruses from Europe and viruses from Asia. And so we can see using these genetic signatures of different viruses that the outbreaks in Milwaukee and Dane counties seem to be a little bit different from each other." 

Friedrich's research found that the coronavirus in Dane County seems to have multiple introductions of the virus, apparently stemming from travel to Europe. In Milwaukee County, there's a strain of virus related to those found in Europe, but there's another strain Freidrich describes as "unique in the global genetic context." That unique strain was likely introduced early on in the epidemic, either stemming from Asia or from the western United States. 

So, why does it matter that the virus in Dane County generally comes from a different source than the virus in Milwaukee County?

"That suggests to us there's not been a significant amount of mixing."

"That suggests to us there's not been a significant amount of mixing. So, people from Milwaukee would have had to come to Madison, breathe viruses out here, and get people infected here. And we would see a genetic signal of that in our data, but we don't see that," Friedrich explains.

If there had been more mixing inside of the state, we would expect to see more people in Madison infected with the same strain of COVID-19 that is present in Milwaukee. Now that the statewide safer-at-home order was struck down, Friedrich says it seems likely that more people will be sickened if people don't continue to take these precautions. 

"The fundamentals of this situation have not really changed, other than the fact we've flattened the curve through our own behavioral choices and we can unflatten it," he says. 

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