Viral Shedding Without Symptoms, Cruise Quarantine, Asymptomatic Testing (Lecture 22)
Welcome to another MedCram lecture. And we can see here the numbers are increasing, but slowly. Here on the WorldOmeter website, 75,730 total (confirmed cases); deaths 2128; recovered 16,000. If we look at the Active Cases and the Closed Cases, you can see that the number of recovered has gone up slightly, and seems to be doing that on a daily basis. If we look at the total worldwide cases, you can see here that they are dwindling overall, but in looking at the cases that are outside of China, we can see that they continue to increase. In terms of the number of deaths, unfortunately, those continue to be increasing pretty much at a linear rate.
I want to update you on the situation with the Diamond Princess cruise ship that’s docked outside of Japan. There was a statement put out by the CDC commending the government of Japan for the fact that they quarantine patients, but there’s been a lot of international criticism of how Japan actually handled this. And there’s been an intervention, and basically the consensus, if you read between the lines, is that this did not work very well. This currently has more than a hundred US citizens either onboard the Diamond Princess or in hospitals in Japan.
And they’ve been placed on restrictions, and they’re saying that they will be required to wait 14 days before coming home, before they’re permitted to go onboard flights. However, if an individual does make it to the United States before that 14-day period ends, they will be subject to a mandatory quarantine until they completed that 14-day period. So the CDC is coming out with that statement, and they want to make sure that everyone is aware that they are taking this seriously.
I also want to quickly highlight a letter that was submitted to the New England Journal of Medicine dated yesterday, February 19. It was an interesting look at about 18 patients; nine men and nine women, meeting 59 years of age. And what they did was they looked at viral loads in the upper respiratory tract to see what they were based on when the symptoms began, and now these people from Wuhan, and all of them, except for one, were symptomatic.
There was one person that was asymptomatic, and we’ll talk about that in just a second, but you can see here the graphs of the CT value, which is basically the viral load. And on the x-axis here is the number of days since the onset of symptoms is 0 being here on the far left, and what you can basically see is that the viral load was quite high in the very early days of the symptoms, and then tapers off almost all of them being undetectable here towards 14 days.
Now, please don’t confuse these days as the incubation period. This is nothing to do with the incubation period. This has to do with how long the symptoms last once you get the symptoms. incubation period has to do with how long it is between infection and the onset of symptoms. The other thing to notice here at the bottom is may be difficult to see, but in terms of throat swabs versus nasal swabs, there was a higher viral count in the nasal swabs in general than there was in the throat swabs, meaning that this virus tends to potentially congregate in the upper airways.
There was one patient that was tested and was asymptomatic, and they say here that the viral load that was detected in the asymptomatic patient was similar to that in the symptomatic patients, which suggests that the transmission potential of asymptomatic, or minimally symptomatic patients, and this is confirming what we had discussed earlier at the beginning of this outbreak that potentially can be spread by asymptomatic individuals. And we will put a link in the description below to this article, as well as the CDC article.
Another article that was submitted on the same day yesterday was a perspective that was written by a number of physicians and epidemiologists on their perspective of defining the epidemiology of covid-19, and how more studies are needed. One of the interesting aspects that they mention here is they may need to do testing in people that may not meet the current definitions, which is someone who has traveled from that particular area of China and has symptoms, and they say here key point of these recommendations is that viral testing should not be used only for clinical care.
I think that’s an interesting point. If we really want to find out what the scope is of the infection, especially in China, there’s going to have to be a lot of people who are asymptomatic be tested to see whether or not they had the virus at some point. Anyway, I leave that perspective there for your consideration. In future updates, we will plan on tackling the molecular biology of coronavirus and contrast it and compare it to other viruses, and that might give us a little bit of information about what this virus likes to do. Thanks for joining us.