Flu season is coming and COVID-19 is still here. Can disease forecasts tell them apart?

Photo by Matthew Modoono/Northeastern University

Every year, as winter approaches, the United States gets ready for a potential epidemic. This year, the country is preparing to handle two.

Influenza, or the seasonal flu, kills between 12,000 and 61,000 people in the U.S. annually, according to the Centers for Disease Control and Prevention. The current COVID-19 pandemic has already been responsible for more than 200,000 deaths in the U.S. this year. 

Both viruses attack the respiratory system and can have similar symptoms. For researchers trying to track these viruses and predict their spread, untangling them will be a challenge.

“Something like this is completely unprecedented,” says Alessandro Vespignani, Sternberg Family Distinguished University Professor of physics, computer science, and health sciences, and director of Northeastern’s Network Science Institute. “Having a major pandemic and then trying to get insight on the seasonal flu—it’s a completely new game.”

In a normal year, Vespignani and his team create models that forecast, about four weeks in advance, which states and regions will see spikes in flu cases. This can help health professionals adequately distribute resources and prepare for the virus. To make these forecasts, Vespignani uses data on occurrences of influenza-like illnesses in outpatient care, which is collected by the CDC from healthcare providers across the country.

“In order to have the seasonal flu forecasts, we need to have the seasonal flu data,” Vespignani says. “And here the situation becomes entangled.”

Like influenza, COVID-19 is a respiratory virus. Both viruses can cause fever, cough, fatigue, body aches, sore throat, a stuffy nose, headaches, nausea, and diarrhea. The rate of symptom onset is different, some symptoms are more common than others, and COVID-19 can also cause a loss of taste or smell. But generally, the two diseases are very difficult to tell apart by symptoms alone.

That means researchers like Vespignani, who has also been providing weekly COVID-19 forecasts for every state to the CDC, will be depending on data from testing for both COVID-19 and the flu to stay ahead of these twin epidemics. 

Fortunately, Vespignani says, this may be a mild year for flu cases. The precautions we are taking for COVID-19 will also inhibit the spread of influenza.

“The social distancing that we are doing, and is going on all over the world, and all the ‘non-pharmaceutical interventions,’ as they are called, cut short the flu season during the past winter and has almost annihilated the flu in the southern hemisphere,” Vespignani says.

Influenza spreads through contact with respiratory droplets, which spray out of the mouth and nose when we cough, breathe, and talk. By washing our hands regularly and staying home when we’re sick—as many have been doing in response to COVID-19—we can cut off chains of transmission. In an ordinary flu season, many people don’t take those basic precautions. 

And in response to COVID-19, many of us are taking another step that doesn’t ordinarily occur in the US: We’re wearing masks, which can catch droplets and protect those around us. 

“We are destroying the network over which the flu can spread,” Vespignani says. 

We have another advantage over influenza that we don’t yet have with COVID-19: a vaccine. And healthcare professionals are pulling out all the stops in this year’s campaign to encourage people to get vaccinated. 

“The campaign to get the flu shot has been working, and working very early this year,” Vespignani says. “So I expect that there will be much more compliance with it. Hopefully, we will have a flu season that will be very hard to measure, just because of that.”

For media inquiries, please contact Jessica Hair at j.hair@northeastern.edu or 617-373-5718.