Typical symptoms of the flu, Covid and the common cold all include coughing, sore throat and a runny nose.
And because of that overlap, testing is the only way to be sure, according to Céline Gounder, an infectious disease specialist, epidemiologist and senior fellow at the Kaiser Family Foundation.
"At this stage in the pandemic, it's really difficult to differentiate between the flu, Covid, common colds and even seasonal allergies," says Gounder.
"I, even as an infectious disease specialist who's been practicing for a couple decades now, cannot differentiate just on an exam.
Secondly, the virus has mutated and different variants are going to behave differently," Gounder says.