Flu season is just around the corner, and experts also expect COVID-19 cases to rise as we enter fall. This double whammy could create a “twindemic,” overloading hospitals with people severely ill with either influenza or the coronavirus. But is it possible to have both diseases at the same time, and, more importantly, what will happen to your body if you do?
Though being infected by both viruses at once is possible, it’s probably rare, says Sunjay Mannan, a physician with the Allegheny Health Network in Pennsylvania. A study of 116 COVID-19 patients from April found that about 21 percent were co-infected with some other pathogen. Only one of those pathogens was influenza.
Though there are few known cases of flu and COVID-19 co-infection, experts are probably missing some. “There are people who simply don’t go to the doctor when they have these symptoms,” Mannan says. “Those positives, we would be missing in the data.” It doesn’t help that symptoms are similar for both illnesses, so it’s nearly impossible to tell if a person has both without testing.
The flu season generally starts in October, peaks between December and February, and can trail on until May. COVID-19 didn’t begin to hit the U.S. hard until March this year, when the flu had mostly retired for the spring. This fall and winter will be the first time we see what chaos breaks loose when the flu and COVID-19 run rampant at the same time — including within the same individuals.
There are three main ways that viral co-infection can play out inside the body, Sarah Meskill, a professor of pediatric emergency medicine at Baylor College of Medicine in Texas, told Fatherly in an email. First, one virus may dominate over the other, so there is only one main infection. Second, the viruses may help each other replicate inside the body, which can make both infections worse. The third possibility is the most common: The viruses co-exist without affecting each other much.
Some experts think that when you get infected by either influenza or the coronavirus, your body ramps up your innate immune system, which can attack any virus. When the second virus infects you, you’re then better able to fight it off. Other experts think that co-infection of these two could worsen symptoms, especially because both viruses attack the lungs.
But co-infection isn’t the main concern for the upcoming flu season. Experts are worried that hospitals will be overloaded with sick patients. “Inner-city hospitals struggle every year taking care of the flu,” Mannan says. The mortality rate in nursing homes is high, and medical experts fear that the “twindemic” may take an especially nasty toll on the elderly.
The good news is that flu season could be mild because of social distancing and mask precautions. And Australia’s flu season (April to October with an August peak) was mild this year, which bodes well for the U.S. But we don’t know anything for sure. Part of the reason public health officials are so concerned is there’s no precedent for how this will play out. “That’s the concern: the unknown,” Mannan says.
There’s not enough information available at the moment for Mannan to be able to recommend people get a COVID-19 vaccine when it’s available, he says. He will have to wait to see the data himself once trials are finished. But he does recommend the flu shot, which the Centers for Disease Control and Prevention is pushing for nearly everyone older than 6 months of age. Even if you expect you could walk off the flu, get the shot, because it’s not just about you. “With any vaccine, the key thing is herd immunity,” Mannan says. “We’re trying to protect those in the community who are truly at risk.”