FACULTY Q&A

Joseph Eisenberg

As the coronavirus continues to spread, a University of Michigan School of Public Health expert discusses the virus transmission and virulence.

Joseph Eisenberg, the John G. Searle Professor of Public Health and chair of the Department of Epidemiology, is an expert on infectious disease epidemiology. He is part of a group of scientists who are involved with the Modeling Infectious Disease Agents Study, an NIH-funded program that focuses on infectious disease transmission modeling with a particular focus on waterborne pathogens. Their work has informed recent Ebola projections about infection rates and deaths.

How concerned should we be about the coronavirus?

Individuals that live in Ann Arbor and throughout the U.S. should be more concerned about the flu and other respiratory illnesses. Tens of thousands of people die every year of the flu. And since it’s flu season, that’s at the top of our concerns right now. In contrast, there’s around 425 documented deaths of those with coronavirus, only two outside of China. So we should keep these risks in perspective compared with risks of other endemic pathogens circulating in the community.

What does it mean that coronavirus is an international public health concern?

It means we should be concerned about the potential for substantial coronavirus transmission outside of China. Right now, almost all the cases are in China, almost all of the transmission is in China and almost all the deaths are in China.

Most of the cases outside China have been isolated cases. That means they got the infection in China and then traveled back to their home and got sick. Now, there’s a handful of transmission events in Japan and one actually in Chicago. So that’s concerning, but cases are still almost all contained in China.

The WHO is not yet calling coronavirus a pandemic, which is what happened with SARS. They’re likely going to wait until there’s more deaths and more transmission outside of China. As long as it’s contained in China, it will be labeled an epidemic.

What lessons learned with SARS are applicable now?

We learned about the importance of isolation with SARS. Right now, the world is trying to isolate transmission by limiting travel. We’ll see how well that works. It’s important to know that since the incubation period is a few weeks, the impact of what you do now won’t be visible for a few weeks. We are seeing lots of comparison of this new coronavirus with SARS. It seems to be a little less virulent than SARS with similar or greater transmissibility.

Why do we see these viruses come from animals?

The fact that more worrisome and more virulent infectious diseases are the ones that have recently spilled over from animals is because there has been little opportunity for humans and these pathogens to adapt. Killing the host is usually a bad thing from a pathogen perspective, and those pathogens that have sustained transmission generally evolve towards being less virulent. Therefore, a pathogen that cannot be transmitted from host to host is often more virulent.

Eastern equine encephalitis is a good example. Transmission occurs among birds, and these infections are not virulent. But in humans, EEE has a 33% mortality rate of those that get ill. In Michigan last summer, EEE caused six deaths

There are coronaviruses and other pathogens that are infecting people in markets in China all the time that we don’t observe. It’s a rare occasion where one of those pathogens infects a human and is able to transmit to other humans. This new coronavirus and SARS are two examples of this phenomenon and are the pathogens we tend to observe in humans. We tend not to see the other pathogens that may cause severe illness but do not transmit human to human.

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• Note: U-M experts are available to discuss the coronavirus and its implications from a variety of perspectives