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Brown School of Public Health   The Rockefeller Foundation

why asymptomatic
testing

How do I know if I am a silent spreader? Should we now all get tested all the time? Does getting tested lower my risk of getting infected?  This primer, which you can also download as a PDF, answers key questions about asymptomatic ‘screening’ testing. 

What is asymptomatic spread?
Many studies now show that one out of two infections in this pandemic comes from someone who didn’t have any symptoms when they passed along the virus. This is called asymptomatic, or silent, spread. Asymptomatic spreaders fall into two categories: 1) People who never develop symptoms of COVID-19 and 2) People who are presymptomatic, meaning that they don’t have symptoms when they infect others but later fall ill. Both types of asymptomatic spread involve infecting others while feeling healthy.

What is asymptomatic, or ‘screening,’ testing?
Asymptomatic testing, also called screening, surveillance or assurance testing, is testing for people who feel healthy. Unlike diagnostic testing, which focuses on people who have COVID-19 symptoms, asymptomatic testing is for those who do not have symptoms but still should get tested. Screening is especially important for anyone engaged in activities that increase the risk of infection, or anyone who works in a high-risk environment.

Testing people who are asymptomatic is an essential part of our collective efforts to stop the invisible chain of transmission.

What are cities and states doing to increase asymptomatic testing?
Many cities and states are building up the capacity to more frequently test people who don’t have symptoms, and make testing accessible for those who are at risk. This includes plans for increased routine testing of people who work closely with others, for example, in restaurants or food processing, and for people who work or live in high-risk environments, such as nursing homes, schools or correctional facilities. In communities hit especially hard, testing campaigns encourage testing for all community members.

What is routine testing?
Routine testing is a crucial part of asymptomatic testing and allows important workplace and community monitoring. It means that people get tested once or twice per week, or every other week, on a regular basis. This is because a test is only a snapshot in time—you can test negative one day, but positive a day later. Routine testing works by finding infections early in groups of people who are at higher risk because of where they work or live. Some universities and colleges, for example, use routine testing of all students and staff who are on campus for in-person learning to avoid outbreaks and stop silent spread. Routine testing is not always necessary for individuals. If you have had one particular high-risk encounter, getting tested 5-7 days later to find out if you got infected is usually sufficient.

What can I do to stop asymptomatic spread?
Whether or not you have had a negative test yourself, it is essential that you continue to follow social distancing, handwashing and mask-wearing guidelines, and stay informed about when and why to get tested. If you have attended a large gathering, forgot to mask up at an indoor event or work closely with others, for example, it might be time to get tested. Stay informed and know your status.

How do I know if I am a silent spreader?
Remember that feeling healthy is not a guarantee that you do not have COVID-19. The only way to truly know is by getting tested. And even then, the test only represents a moment in time. If you think there might be a chance you caught the virus, stay away from others, mask up and get tested.

How do I know if and when I should get tested?
Common reasons for healthy people to get tested include: You went to a gathering and got very close to people who do not live in your household, you work in an essential industry, or you have an underlying medical condition and may have been exposed, you recently traveled, or you haven’t always worn a mask or social distanced.

Remember that feeling healthy is not a guarantee that you do not have COVID-19. The only way to truly know is by getting tested.

Should we now all get tested all the time?
No. The availability of asymptomatic testing does not mean everyone should get tested all the time. It means that we strategically test those who are at higher risk, and test them either routinely because they work in essential settings or just once after a high-risk encounter. Check your city or state’s website for more details on asymptomatic testing guidelines in your area.

Does getting tested lower my risk of getting infected?
No. A COVID-19 infection comes from having been exposed in a high-risk environment. Large-scale asymptomatic testing can bring down overall infection rates by identifying sick people in the community. But testing will not protect you from getting the virus, in the same way that a pregnancy test can only confirm a result, not prevent it.

Why are some people at higher risk of getting COVID-19?
For grocery store workers, first responders, nurses, teachers doctors and many other essential workers, being potentially exposed to COVID-19 is an unavoidable part of their job. They risk infection every day to prepare our food, take care of the sick and keep our cities safe. For others, being at higher risk is a choice. An outbreak can come from actions that promote infection instead of preventing it, such as having friends over indoors without masks. Make sure you don’t take unnecessary risks. Do your part, mask up, social distance, wash hands, avoid from indoor, crowded gatherings and get tested if you think you may have been exposed.

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