WHO walks back comments on asymptomatic coronavirus spread, says much is still unknown
So the asymptomatic are not believed to be big transmitters, yet what about those who are asymptomatic until they become symptomatic?
Are pre-symptomatic people big spreaders? And how does anyone know if they are asymptomatic or pre-symptomatic until symptoms show up or not, once given enough time?
I am not against the WHO, yet I can see why there is a lot of confusion about what they seem to be trying to convey.
The confusion IMO is related to how the media focuses on a small part of a larger answer using their various political agendas to reach unwarranted conclusions.
This was the original question:
"We had a story out of Singapore today saying that at least half of the new cases, they’re seeing have no symptoms. And I’m wondering if it’s possible that this has a bigger role than the WHO initially thought in propagating the pandemic and what the policy implications of that might be. Thank you."
Here is the answer. Doesn't make for much of a headline. Note the distinction between asymptomatic, presymptomatic and those with very mild symptoms. But from th NEJM article I posted earlier, the mechanism for asymptomatic transmission exists and its had to argue their conclusion that the initial rapid spread of the disease was largely due to asymptomatic carriers.
Dr. Maria Van Kerkhove:
"So I can start and perhaps Mike would like to supplement. So there’s a couple of things in the question that you just asked. One is the number of cases that are reported that are being reported as asymptomatic. And so we hear from a number of countries that X number, X percentage of them are reported as not having symptoms or that they are in their presymptomatic phase, which means it’s a few days before they actually develop severe symptoms. In a number of countries when we go back and we discuss with them one, how are these asymptomatic cases being identified? Many of them are being identified through contact tracing. And so, which is what we would want to see and that you have a known case, you find your context, they’re already in quarantine, hopefully and some of them are tested. And then you pick up people who may have asymptomatic or no symptoms or even mild symptoms."
"The other thing we’re finding is that when we actually go back and say, how many of them were truly asymptomatic, we find out that many have really mild disease, very mild disease. They’re not ‘COVID’ symptoms, meaning they may not have developed fever yet. They may not have had a significant cough, or they may not have shortness of breath, but some may have mild disease. Having said that we do know that there can be people that are truly asymptomatic and PCR positive. The second part, your question is what proportion of asymptomatic individuals actually transmit. So the way that we look at that is we look at, these individuals need to be followed carefully over the course of when they’re detected and looking at secondary transmission."
"We have a number of reports from countries who are doing very detailed contact tracing they’re following asymptomatic cases. They’re following contacts and they’re not finding secondary transmission onward, is very rare. And much of that is not published in the literature. From the papers that are published, there’s one that came out from Singapore, looking at a longterm care facility. There are some household transmission studies where you follow individuals over time and you look at the proportion of those that transmit onwards. We are constantly looking at this data and we’re trying to get more information from countries to truly answer this question. It still appears to be rare that an asymptomatic individual actually transmits onward."
"What we really want to be focused on is following the symptomatic cases. If we followed all of the symptomatic cases, because we know that this is a respiratory pathogen, it passes from an individual through infectious droplets. If we actually followed all of the symptomatic cases, isolated those cases, follow the context and quarantined those contexts, we would drastically reduce. I would love to be able to give a proportion of how much transmission we would actually stop, but it would be a drastic reduction in transmission. If we could focus on that, I think we would do very, very well in terms of suppressing transmission. But from the data we have, it’s still seems to be rare that an asymptomatic person actually transmits onward to a secondary individual."