How Coronavirus Tests Actually Work

What happens when you get a COVID-19 test?

First, a medical professional puts a swab — an extra long, one-headed Q-tip — way, way, way up your nose. That captures viral particles, along with a bunch of other stuff that Dr. Davey Smith, a research virologist at the University of California, San Diego, referred to as “biological gunk,” like mucus and random cells. The next step, Smith said, is isolating the viral RNA — the genetic material that the virus uses to replicate itself. The RNA in a virus like the one that causes COVID-19 is similar to DNA, but instead of the twisted ladder of a double helix, it’s half that because it’s split down the middle. Some viruses carry their genetic code as DNA, but RNA viruses mutate a lot faster. That feature helps them jump species and evade both...

What happens when you get a COVID-19 test?

First, a medical professional puts a swab — an extra long, one-headed Q-tip — way, way, way up your nose. That captures viral particles, along with a bunch of other stuff that Dr. Davey Smith, a research virologist at the University of California, San Diego, referred to as “biological gunk,” like mucus and random cells. The next step, Smith said, is isolating the viral RNA — the genetic material that the virus uses to replicate itself. The RNA in a virus like the one that causes COVID-19 is similar to DNA, but instead of the twisted ladder of a double helix, it’s half that because it’s split down the middle. Some viruses carry their genetic code as DNA, but RNA viruses mutate a lot faster. That feature helps them jump species and evade both natural and medical efforts to kill them. Influenza, for instance, mutates so quickly that we need a new vaccine for it every year.

Just like DNA can identify a person, RNA can identify the virus that causes COVID-19. Isolating it requires a series of steps...