We've heard a lot about coronavirus testing over the past few months. We've heard about shortages of tests. Faulty test kits. And people denied testing because they weren't sick enough. But how do coronavirus tests even work? It's complicated. (1/23) 
In order to fight a pandemic, you have to know who's infected. That enables you isolate those who are sick, and quarantine those who might be. But the novel coronavirus is just that: novel. We didn’t have a test for it at first — so researchers had to make a new one. (2/23)
After the coronavirus was detected in China, officials shared the viral genome – essentially, the genetic blueprint for the virus. That was important, because it let researchers around the world design tests that looked for snippets of that genetic material. (3/23)
This kind of test, which usually uses a technology known as rt-PCR, should be able to identify whenever someone is shedding the coronavirus. Just like how each species has unique DNA, every virus has a unique genetic code (in this case, RNA). (4/23)
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cnn.it/3e8w4ND
If the test finds pieces of that code in a patient's sample – like a nasal swab – then they're considered infected. The test itself takes anywhere from a few minutes to a few hours to run, but it can sometimes take days to get results. (5/23)
That's important for a couple of reasons. If somebody is suspected of having the virus, doctors will have to take extra precautions. That means using valuable protective equipment – like masks and gowns – even if the patient ends up testing negative. (6/23)
And if somebody actually does have the virus – but can't get test results for days – then they may not take the precautions they should. Luckily, testing capacity in the US has increased, but officials are still reporting unacceptable delays around the country. (7/23)
But there's another type of test that you'll probably be hearing a lot more about: antibody tests. These are blood tests, but they don't actually test for the virus itself. Instead, they look for your body's immune response to the virus – antibodies. (8/23)
These tests matter because they can identify who's been infected in the past. That lets researchers understand how prevalent the virus really is or was – including among people who showed few or no symptoms. (9/23)
Antibody tests tell us something else, too. They let us know who might be immune to the virus – in other words, who might be protected against getting infected in the future. (10/23)
Most experts think that after someone recovers, they'll probably have some sort of protection against the new coronavirus. But how long that immunity will last, and how strong it'll be, is still unclear. (11/23)
There are dozens of antibody tests out there, and so far one has been authorized by the FDA for clinical laboratory use. That's important — because there are a number of companies making false claims about their own tests, which can be dangerous. (12/23)
False positives – a test that mistakenly says you have antibodies to the virus – can give people a false sense of security, making them think they're immune when they're not. (13/23)
And false negatives are problematic as well. Even high-quality antibody tests might miss circulating antibodies because our bodies can take some time to produce them. (14/23)
That's why antibody tests alone shouldn't be used to diagnose or exclude a previous infection, at least for now. But they're still useful, and they're key to understanding just how widespread the virus really is. (15/23)
Dr. Anthony Fauci, the director of @NIAIDNews, told CNN this morning that “a rather large number” of these tests will be available within a week or so. (16/23)
And hopefully both of these types of tests do become more widely available. Remember, none of this matters unless people can actually get tested on a mass scale. (17/23)
That doesn’t mean everyone needs to be tested, but millions more tests will need to be performed to understand how widespread the infections really are. (18/23)
Bottom line: If we're going to start lifting social distancing measures – whether in a few weeks, or a few months – we'll need the capacity to test aggressively. (19/23)
We’re not there yet. There are places in the US where people can get tested at drive-through sites – but there are also places where it’s extremely difficult to get a test unless you’re hospitalized. And the US still hasn’t run as many tests per capita as hard-hit Italy. (20/23)
That will need to change when we start to re-open this country. We’ll need to identify any new cases quickly. We'll need to isolate those who are infected. And we'll need to figure out whom they've had contact with. (21/23)
Test and Trace and Treat. That’s how we’ll prevent – or limit – future surges. (22/23)
The US made mistakes in the early days of this outbreak. We took too long to distribute tests. And we missed early cases. But there's still time to improve. If we ever want to get back to normal, we'll have to. (23/23)
