In January, the “novel coronavirus” that had emerged in the Chinese city of Wuhan was at most a distant concern for many people in the United States.
However, SARS-CoV-2, the coronavirus that causes COVID-19, was already circulating in major US cities, according to Alessandro Vespignani, Sternberg Family Distinguished Professor, who directs Northeastern's Network Science Institute. And if we want to keep our communities safe in the future, we need to understand how we missed a virus that was right under our noses.
“We don't want to fall into that trap in the future,” says Vespignani.
The discovery that the virus was already circulating in the US in January comes from a model that Vespignani and his colleagues use to study and predict the global spread of the virus. The model is based on human mobility and interaction patterns, as well as virus infection dynamics.
Alessandro Vespignani is the Sternberg Family Distinguished Professor of Physics, Computer Science, and Health Sciences and director of the Network Science Institute at Northeastern. Photo by Adam Glanzman/Northeastern University
“The model allows us to go into what we call the invisible stage of the epidemic in the United States,” says Vespignani. “We can simulate the arrival of infected people starting local chains of transmission.”
I researched that team released last month shows that the blockade of cities within China, as well as travel restrictions implemented by countries around the world, came too late. The coronavirus was already out.
But how did we miss it? Why didn't we notice that people were getting sick?
“There was no large-scale testing capacity in the US and Europe, and the guidelines were to test only people with a history of travel,” says Vespignani. “But when you get an infection from someone who's already in the United States, you don't have a travel history.”
It was January—the height of flu season, winter colds, and other respiratory illnesses. Even the few people with severe cases would not have attracted much attention without a history of recent travel to China.
“So what happened is that for a month and a half, the epidemic went unnoticed,” says Vespignani. “Until you have a critical mass of cases. Then, at that point, you start to see the tip of the iceberg.”
Cities that are hubs for international travel from China—New York, Seattle, San Francisco, Los Angeles—had the first cases in the US, but similar chains of infection were starting around the world. By the time the US turned away or quarantined travelers from China, the coronavirus had already spread to US cities and new cases came from Europe and other regions.
Given the change our lives have undergone in recent months, looking back on January may seem like ancient history. But understanding how and when these outbreaks started can help researchers make predictions down the line.
“If I have an outbreak that starts in early January, I can project a certain trajectory. if I have an outbreak that starts at the beginning of March, everything changes by two months,” says Vespignani. “It's infinite time for a disease like this. You really want to be as sharp as possible, down to the one-week level, so that you have the right timing now to inform what we're going to see in the coming weeks or months.”
And what researchers are learning will also help us make smart decisions when the number of infections has declined and we begin to lift physical distancing measures.
It wasn't enough to just test for the virus based on travel history to national or international hotspots, Vespignani says. If we don't have more extensive testing and the ability to trace the contacts of every infected person, a second wave of infection could be created without us knowing.
“We don't want to be in the same situation,” says Vespignani. “We need to have all of these so that we can make visible what, in the first place, could be invisible.”
For media inquiriescontact Jessica Hair at j.hair@northeastern.edu or 617-373-5718.
