Funding for NOVA Next is provided by the Eleanor and Howard Morgan Family Foundation. I know that last part is particularly confusing. Image Credit: NIAID, Flickr. After gathering proteins to build a template of itself, it then hijacks every possible process in that cell—the processes that make it a liver cell, say, or a lung cell—and turns it into a virus factory. But a standard COVID-19 test (the PCR-based swab) can’t tell the difference between the battlefield debris—which is still recognizably RNA from SARS-CoV-2, even though it can’t make anyone sick—and a viable virus that can still infect someone. Tests for COVID-19 are mainly done on people who are sick (have symptoms of COVID-19). All this is made doubly complicated because early research suggests that people who are pre-symptomatic—that is, who are infected but have not yet developed symptoms—contribute to around half of all COVID-19 transmission, Pitzer says, while those who will never develop significant symptoms (between 20% and 60% of COVID-19 cases) likely contribute less to the virus’s spread. Reason: testing done during the first 5 days after exposure will usually be negative. So, if you’ve been exposed and are showing COVID-19 symptoms, that would be the ideal time to get tested. Maybe a colleague at the grocery store where you work develops symptoms after you spent a full shift together yesterday. That brings us to a question I’ve heard many people ask—and asked myself—in the last several months. (That’s also, for the record, the reason behind news stories claiming viruses can survive for weeks on certain surfaces. However, there are no set guidelines for when a person with a known exposure should be tested for COVID-19, and a negative result early on in the two weeks after exposure is … As with many complicated topics, it’s best if we start by defining our terms. Typically, it takes at least a few days for the virus to show up in your system. When it comes to most of the viruses in our body, this is usually the end of the story. On the aircraft carrier that hosted an outbreak last fall, for example, young sailors were sleeping on bunk beds, 20 to a room. The problem is that the primers used to work with this part of the RNA tend to stick to each other instead of to the virus, preventing effective replication and leading to more false negatives. A viral test tells you if you have a current infection. There’s a lot we still don’t know about COVID-19, but the answer is: probably not. Other World Health Organization member countries have added different primers to their tests to try to circumvent this issue, but many of the labs running PCR tests in the U.S. haven’t done so yet. “Nobody has bajillions of viruses in their respiratory tract and is not feeling it at all.”, She attributes situations where asymptomatic spread occurred to specific, high-risk circumstances. You think you should get tested, and you’ve heard you shouldn’t do it right away, but you’re not exactly sure why that is or what the best approach might be. If the enzyme isn’t there, the virus may only make it this far. And the swab that went up the patient’s nose or into their mouth might not have reached the spot where the virus was replicating—especially if that replication was happening deep in the lungs. Image Credit: martin-dm, iStock. We go on as if nothing happened.”, Masks have proven to be a powerful tool in curbing the spread of the coronavirus through droplets and aerosols. Get a test on day 6-8 after exposure. While you wait to get the test, you should quarantine in case you do have COVID. But the infected person doesn't begin producing antibodies immediately. One of the things that has made dealing with COVID-19 so difficult is that many infected people shed lots of active, infectious virus before developing symptoms, or without developing symptoms at all—meaning they can silently spread the virus. Viral replication is hard on cells and can cause early death and disintegration, leaving infectious viruses floating freely in your system to look for new targets. Shedding a virus means that there is a sufficient amount of virus circulating in your system—in the case of SARS-CoV-2, in your mucus and saliva—that it might escape your body and go elsewhere. Guidance until now had recommended quarantining for 14 days after exposure to a coronavirus-infected person within 6 feet for a total of 15 minutes. You can be tested for COVID-19 at any time, but keep in mind that the tests are more reliable when people are actually showing symptoms of infection. It’s natural that “people want to be given one number, but there’s no one number,” he says, “because we all receive different infectious doses.” Some people might test positive two days after exposure, others might wait 10 days. “It’s how much virus you have, but it’s also the context in which you are,” she says. And a recent preprint study looking at strategies for shortening quarantine periods suggests that the optimal time for testing is day 6 or 7 after exposure. Quite the dramatic ramp-up. For Pitzer, best practices would be getting tested on day 3 or 4 after an exposure and then again between days 7 and 10. People who develop symptoms again within 3 months of their first bout of COVID-19 may need to be tested again if there is no other cause identified for their symptoms. People who have tested positive for COVID-19 within the past 3 months and recovered do not have to quarantine or get tested again as long as they do not develop new symptoms. “Eight hours, 16 hours, then it crosses a critical threshold and starts going up.” Once SARS-CoV-2 has established its first few cellular factories, things begin to move quickly. Additional funding is provided by the NOVA Science Trust. “There’s no international committee on viral language,” Lee says with a laugh.). “Our body is not a hospitable environment,” Messaoudi says. We recommend getting tested about five days after exposure. The red spikes represent spike proteins, which can help the virus gain entry into a host cell by linking to its ACE2 receptors. It can let people know of possible exposures before any symptoms appear. Figuring out when to get tested after exposure requires understanding what happens once the virus enters your body. Doctors are sharing … For purposes of contact tracing in the U.S., an “exposure” to COVID-19 involves having spent more than 10 minutes at less than 6 feet from someone who is infected while wearing no personal protection, says Ilhem Messaoudi, a viral immunologist at the University of California, Irvine. You can change your choices at any time by visiting Your Privacy Controls. Ultimately, “it’s just a bit more sure.”. “It’s like how with a zipper, you need that bottom part to latch one side to the other,” Messaoudi says. For the two to fuse, and the virus to access the cell, a special enzyme must be present at the site to help the process along. “Viruses replicate exponentially,” Lee says. These are all ways to potentially get virus on yourself,” says Yale University epidemiologist Virginia Pitzer. self-quarantine at home for five days, then get tested; self-quarantine at home for at least 10 days, if you don’t want to get tested and remain symptom-free; People may spread COVID-19 as soon as two to three days before developing symptoms which occur on average 5 to 7 days after exposure, with some cases lasting as long as 14 days. “It’s not just pouring out of you.”. At a certain point, though, symptoms start coming both from the physiological stress of the battle your immune system is waging and from damage wrought by the virus itself. Information about your device and internet connection, including your IP address, Browsing and search activity while using Verizon Media websites and apps. Tests are even more accurate when patients are exhibiting symptoms. If you don’t have that, you can’t zip your jacket.”. The Secret Life of Scientists and Engineers. Studies of fluid dynamics as well as individual COVID-19 cases have suggested that, under specific conditions, the virus can travel significantly farther than 6 feet, and possibly even infect new hosts in as little as five minutes.). But as a general rule, “greater frequency is important; it scales with the risks,” Pitzer says. It can take as long as three weeks for a blood antibody test to turn positive. It can mean 100 or 1,000 times the amount.”, (Messaoudi is careful to note that people in her community don’t talk about latent periods because “latency” in HIV and other similar viruses refers instead to the time a virus can survive undetected in a body after infection. Those membranes naturally repel each other, like oil and water, says Benhur Lee, a virologist at the Icahn School of Medicine at Mount Sinai. It can take almost a week after exposure to COVID-19 to register a positive test result. Eight days after exposure, the test only has a 20 percent chance of showing a false positive. We’ve got you covered. That’s why coronavirus patients often test positive for weeks or months after infection, but it doesn’t mean they’re still contagious. If you have COVID but get tested before then, you may not have enough of the virus … All of this is to say that a person who thinks they might have been exposed to the coronavirus should wait a few days, to give the hypothetical virus time to develop through its latent period. What does it mean to be “exposed” to a virus? It’s one more of those frustrating variables of COVID-19. If you get a … That’s not always a given. After the interferon alarm goes off, what she calls the “heavy artillery” arrive: a dramatic burst of T-cells that go around killing all the cells in your body that are harboring virus. That aftermath is also what causes symptoms to continue even after an infection is controlled. We and our partners will store and/or access information on your device through the use of cookies and similar technologies, to display personalised ads and content, for ad and content measurement, audience insights and product development. The recommended timeline of those two tests varies a bit—but we’ll get to that. If the sample wasn’t stored at the right temperature, the genetic material might be too degraded to replicate. The three experts interviewed for this article recommended getting tested twice, which allows for the inherent variability in viral load and in everyone’s immune systems, and for false negatives. This alarm comes in the form of type-1 interferon, a protein that triggers the arrival of powerful immune cells that can chop up viral RNA and deprive the virus of proteins essential to its replication. Messaoudi draws a more nuanced conclusion. An antibody test might tell you if you had a past infection. Receive emails about upcoming NOVA programs and related content, as well as featured reporting about current events through a science lens. It’s about the physics of those actions—the propulsive air is necessary. COVID Alert. One hypothesis suggests those individuals may be genetically predisposed to tolerate the disease, making small changes in the body’s mechanisms to counteract negative effects while the immune system fights the virus. A viral infection ends once your body kills all remaining functioning viruses, putting an end to their replication. Your respiratory cells can start to fall apart, letting liquid and more virus into your lungs and starting a dangerous cycle of destruction. In the case of SARS-CoV-2, the virus often goes undetected by the immune system for more than three days. “What’s more informative is if you truly self-quarantined for 10 days,” Lee says. Research has shown that people who become ill develop symptoms, on average, between five and six days after becoming infected. To start, a virus entering a body faces many physical obstacles. In the case of SARS-CoV-2, the virus that causes the COVID-19 disease, the spiky outside proteins allow it to attach to a human cell by linking to a protein that sits on the outside of many cells called ACE2. But both the virus and the cell are still separate at that point, each inside its own fatty membrane. Serious symptoms. Hilary Brueck . If a viral infection is a battle, “when you start developing symptoms, that means the immune system is losing a little bit of ground,” Messaoudi says. But not every cell has machinery that’s suitable for reproducing viruses. Even if that attack is successful and there aren’t any more infected cells to kill, there’s plenty of bits of virus floating around in the chaos—manufacturing errors that won’t ever replicate, pieces of genetic material left over from the inside of cells that died. National corporate funding for NOVA is provided by Draper. When should I be tested? What does a viral infection actually mean, and what determines if you’ll get one when you’re exposed? How soon after exposure can you be tested? (Though it’s useful for epidemiological purposes, note that this contact-tracing definition of exposure doesn’t encompass every possible way that infection can occur. “Disease is interplay between host and virus; it’s not just about underlying health factors,” he told me. CDC allows shorter quarantine: 10 days after exposure to COVID-19, 7 days with a negative test. You probably know this much already. An artist rendering of SARS-CoV-2 virus particles. “No, you haven’t found virus in cruise ships three weeks later, you found viral RNA,” Messaoudi says. Find out more about how we use your information in our Privacy Policy and Cookie Policy. National overview of testing; COVID-19: Testing and reducing stigma (printable poster) COVID-19: Prevention and risks “Your body opens up its blood vessels to let those molecules through. Confusing but true: At first, symptoms of an infection are caused by your immune system, not by the virus itself. In that way, testing can be a useful tool, especially in situations where you might have been exposed but you’re not sure. Major funding for NOVA is provided by the David H. Koch Fund for Science, the Corporation for Public Broadcasting, and PBS viewers. If SARS-CoV-2 does succeed in hijacking a cell's machinery, then it’s well on its way to infection. The diagnostic test, known as a “PCR test,” works by detecting genetic material from SARS-CoV-2, the virus that causes COVID-19, in the nose and upper … And if the test is negative, can I end my quarantine early? But even as he gives his recommendation, Lee remains concerned about overgeneralization. Testing is routinely performed on patients who have serious symptoms or are admitted to the hospital. But crossing that “critical threshold” of exponential replication prompts the cells in the infected area to send out an alarm, alerting neighbors to a possible intruder. That's why it is not useful as a diagnostic test for someone with new symptoms. All this is happening under the immune system’s radar. “You’re not a living organism, so you’re completely dependent on having access to what we call a ‘susceptible’ cell, or one that can be infected and support your replication.” Even if a human breathes some amount of virus in—or rubs some in her eyes, or licks some off her fingers—that doesn’t always happen. “When it enters the cell, it kind of disrobes,” Messaoudi says, releasing its genetic material, called RNA. But for most of us, vaccination is still a ways off, and navigating our pandemic world safely is more important than ever—especially as infections spike around the country and winter makes it more difficult to do things outside. Two kinds of tests are available for COVID-19: viral tests and antibody tests. “If you get exposed and the virus replicates faster than the immune system can respond,” Messaoudi says, “then the virus is advancing and your immune system is working—it’s a double whammy.”. Consider downloading and using the COVID Alert app. It’s so obvious!”, Still, unless you’re at peak infectiousness, “if you’re keeping your mouth closed and wearing a mask, it’s likely you shed a lot less than if you’re actively sneezing, coughing, singing, shouting,” Pitzer says. The Minnesota Department of Health recommends testing "five to seven days after" an exposure event.