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The main downside of PCR tests, though, is that they have to be run on special machinery in a lab, which makes them impractical in many parts of the world. The analysis itself takes only a few hours, but if there's a backlog--as there often has been during COVID--you may not get your results for days or even weeks. Given how easily COVID is passed from one person to another, any test result you get more than forty-eight hours after giving the sample is useless: If you're going to spread the virus, you've already done it by then, and if you need to start treatment with an antiviral or antibody medication, you have to do it within just a few days of the infection. The other main category of tests looks not for the virus's genes, as PCR machines do, but for specific proteins on its surface. These proteins are known as antigens, and so the tests are called antigen tests. They're less accurate, but not egregiously so; they're especially good at detecting when you're capable of infecting others, and they produce results in less than an hour (and often within fifteen minutes). Another benefit is that some antigen tests can be taken by anyone in the privacy of their home. If you've ever taken a pregnancy test by peeing on a stick and watching for the smiley face to appear, you've used a thirty-year-old technology called a lateral flow immunoassay-- named that way, I suppose, because "test that uses liquid flowing over a surface" was too easy to understand. Many antigen tests work the same way. During an outbreak, we've got to make it easier for everyone to get tested and get results fast--especially if it's a disease that you can transmit to others before you have any symptoms. And by "we," I mean the United States first and foremost. Other countries, including South Korea, Vietnam, Australia, and New Zealand, far outpaced the U.S. in testing and returning results, much to their benefit.