Testing vs transmissibility of COVID-19
For a person infected with COVID-19, what generally is the period of time where:
they are capable of infecting others?
they will test postive for the disease?
In particular, I'm curious if a window exists, and how wide it is, where a person can spread the virus prior to testing being able to catch the person.
Note: I'm assuming that my question is mostly independent from the issue of false negatives — people that get the disease but don't test positive (who will, of course, be able to spread the disease without being identified as having it). If these issues cannot be decoupled, please comment on that in an answer.
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Not everyone follows the same pattern but it looks like in those that become symptomatic, their period of infectivity begins 1-3 days before onset of symptoms. In those that don't have symptoms, this suggests that they also start to become infectious 2-3 days after becoming infected.
People who have positive rtPCR tests are considered non-infectious once those tests turn negative on 2 consecutive occasions 24 hours apart. However, there are exceptions with people with active pulmonary or other disease with negative swabs. A majority of patients will be non-infectious after 21 days. But there are some with severe disease that test positive for a long time. There are cases up to 53 days. Some of those people testing positive many weeks after infection may have RNA fragments being detected in swabs rather than viable virus.
While most studies have looked at respiratory samples, one study looked at fecal samples and found that viral RNA shedding was still occurring after the respiratory tests were negative.
At present we don't have a definitive answer to how long people are potentially infectious after developing COVID-19.
www.stuff.co.nz/national/health/coronavirus/120985003/coronavirus-how-long-are-you-infectious-when-you-have-covid19 www.thelancet.com/journals/langas/article/PIIS2468-1253(20)30083-2/fulltext
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