The short answer is typically, someone is contagious between 5 and 10 days after a positive test. The longer answer is that it will be different for everyone depending on a few factors. Generally the people who are contagious for the shorter end of the range are those who have been fully vaccinated, and whose symptoms are improving. The people who are more likely to be contagious for up to 10 days are those who have not been vaccinated, whose symptoms are not improving, or who have a compromised immune system.
Based on a few important issues, let’s back up and go through all the steps that can help you better understand how long someone would be contagious after a positive result on their COVID-19 testing.
The CDC COVID quarantine guidelines say as soon as you develop symptoms, or 5 days after a COVID-19 exposure if you do not develop symptoms. If you take a test before day 5 and get a negative result, you should take another test on day 5 since you may now have enough of the virus in your system to test positive.
Between two and 14 days after exposure. In early variants of COVID-19, it was most likely symptoms would appear 5-6 days after exposure. However, symptom onset time does vary significantly with disease variants, with Delta being shorter than previous variants and Omicron averaging even less at 3 days.
This period between exposure and symptoms appearing is the incubation period. The CDC warns that the 1-2 days before symptoms begin (so during this incubation period) are high transmission times, when someone can be very contagious.
According to the World Health Organization (WHO) the majority of transmissions for COVID-19 are in the 1-2 days before symptoms begin to the 2-3 days after they begin. People are contagious for longer than that, but that is when the majority of people are the most contagious. The best way to predict when you are unlikely to be contagious with COVID-19 any longer is with a combination of your test results, symptoms, and vaccination status.
Day 0 is the day you got a positive COVID-19 test or the day your symptoms started, whichever came first. Let’s look at the recommendations for isolation depending on the situation.
You are very likely to be contagious and it is highly recommended that you stay isolated and quarantined from others.
If you are vaccinated (or have recovered from COVID-19 within 90 days) AND you no longer have a fever without taking fever-reducing medication, you are less likely to be contagious. It is recommended you avoid crowds and travel if possible, and wear a mask around others because it is possible for you to still be contagious, just unlikely.
If you are unvaccinated (and have not had COVID-19 within 90 days) OR you still have a fever OR you are immunocompromised, you are likely to still be contagious. It is highly recommended that you stay isolated and quarantined from others.
The CDC recognizes that retesting after a positive COVID-19 test is an option, but not a requirement. Some people choose to retest around 5 days after a positive test, as a way to get additional information about if they remain contagious in days 6-10. If someone has access to testing and chooses to, a negative antigen (or rapid) test likely means you are no longer contagious.
It is important to note the difference between an antigen (rapid) test and a PCR test for this purpose. An antigen test is essentially checking to see if your swab is teeming with virus, meaning you would likely be contagious. A PCR test is much better at finding traces of the virus, making it much more sensitive. However, because a PCR test is so good at finding even whispers of the virus, it can show a positive result for weeks after infection. Retesting with a PCR test is therefore very likely to give you a positive result if you retest soon after getting a positive COVID-19 test.
Understanding how long someone is contagious with COVID-19 is a huge tool in helping combat this disease. Accurate testing with quick results is another. At BioCollections, we have testing locations throughout the United States and internationally to get you the best information possible about your current health status. Our PCR test, the gold standard of SARS-CoV-2 testing will give you your results in as short as 10-24 hours. Visit BioCollections.com to learn how we can help with your testing needs, or contact us for more information.