Hi catching up in the last thread, but wanted to note from the April 13 WHO PC which I just finished that Dr. Maria said that while the incubation period is up to 14 days, the average onset occurs about 5 to 6 days after exposure:
BBM:
“Sarah: (
37:51)
Thank you. I’m wondering what is the appropriate timeframe for someone to isolate if they think they might have been exposed? There seems to be this belief that 14 days is appropriate, but since the incubation period can be up to 14 days. Then if someone is not showing symptoms after 14 days, but does have the virus and doesn’t have access to a test, how long after that can a person have the illness and be contagious? And then in terms of the reactivation in people, based on your previous response, is it possible for the virus to be latent in someone or are we talking about re- infection?”
“Dr. Maria Van Kerkhove: (
38:33)
Thank you for these questions. Yes, what we recommend for somebody who is exposed to an infected person is that they be followed, that they be quarantined for 14 days.
Most people who are infected with COVID-19 will develop symptoms within five days. That’s the median time, five to six days. But it goes up to 14 days. So 14 days is a good marker. For individuals who are infected, your question was how long can they be contagious? And that’s the right question because when we actually test people who are infected with COVID-19, they have this molecular test, a PCR test, and they can be PCR positive four weeks, but that doesn’t actually mean that they’re contagious for weeks.
So what the PCR does is it measures fragments of the virus, parts of DNA of the COVID-19 virus that is detectable through this molecular test. But it doesn’t actually mean that you’re contagious for that long. What we’ve seen from some preliminary studies, and I’m referring to a study from Germany, is among some mild patients, I believe it was eight or nine mild patients, that they could find live virus for eight or nine days after symptom onset. What we need is much more data from countries to actually be able to say how long is someone contagious.
And so, right now what we have are these PCR tests which suggest that people with mild disease can be PCR positive for two to three weeks. What we need to understand is out two to three weeks, are those people still contagious? Again, this is another example where we don’t have the full picture, but there’s a lot of studies that are underway to give us those answers and so we hope to be able to get back to you with more details on that as soon as they’re available.”
Dr. Michael Ryan: (
40:26)
“On the issue of reactivation and latent infection, there are many situations, particularly in viral infection where someone doesn’t clear the virus entirely from their system. It can happen in the case of immunocompromised people who are sick for other reasons, and then the virus can come back and attack the person again, and that’s sort of seen as reactivation. It’s usually that the virus was never property cleared. There are other situations where someone clears the virus but develops a secondary infection, a secondary bacterial infection, often an influenza, for example. It’s not the influenza infection that causes the problem. It’s very often the secondary bacterial pneumonia. The damage to the lungs and the inflammation create unfortunately an opportunity for bacteria that are normally non-pathogenic, they’re all over the place, but can actually exploit the fact that their lungs are weakened and you end up down with a very high fever again and very sick. But you’re actually not sick with the virus, now you’re sick with the bacterial infection. So there are many reasons why we might see reactivation of infection either with the same infection or with another infectious agents.
The issue of longterm, I think, transmission has been dealt with by Maria. There will always, always, always in health be exceptions. There will always be individuals who may transmit for longer. There may be individuals whose incubation period may be for longer, it may happen. There are outliers in every walk of life. We all know people who are given a year to live because of a cancer diagnosis and they live for 10 years. That doesn’t mean that everyone with that diagnosis live for 10 years. It means one person has lived for very much longer, but on average this is how long people survive. And I think we need to look at that.
These are averages. And then we look at the range around the average and we try to explain that this is likely where the longest or the shortest incubation periods are in reality. But there will always be a chance of an outlier. And I always say, we need to study the outliers. We need to study those who transmit for longer. We need to study those who don’t clear the infection properly because these are very significant events.”
Source / Apr 13 WHO Briefing
We have come a long way since then, and this is not nearly as bad as the plague for most of us. BTW I did briefly ponder how many of us might have been burned as witches back then for our sassy ways.
