As Coronavirus tests become more widely available across the US, scientists have warned about a growing concern: Many people with negative results might actually have the virus.

The majority of tests around the world use a technology called PCR, which detects pieces of the virus in mucus samples. But "there are a lot of things that impact whether or not the test actually picks up the virus," Priya Sampathkumar, an infectious diseases specialist at Mayo Clinic in Minnesota, said.