Q&A of the Day – Who is being tested for coronavirus & how many go undetected?
Each day I’ll feature a listener question that’s been submitted by one of these methods.
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Today’s entry: Try this: Because so many people have mild to moderate symptoms and simply assume they either have a cold or fever, they often don’t even consider getting tested. So, your sample size is mainly from the very vulnerable or those who have been forced tested such as on cruises. Your sample size isn’t representative of the infected, it’s representative of the sick. For this virus, that has been noted as potentially two different categories. Am I lying?
Bottom Line: You have a good point. We only can monitor the outcomes of those who’ve been tested. While we don’t know what we don’t know – we do have data on how many tests have been administered and what the outcomes of those tests were. Based on worldwide testing data in the top five countries for total COVID-19 cases – China, Italy, South Korea, Iran and Spain – about one half of one percent of the population has been tested. By far the highest concentration of positive cases, based on population, has been Italy. They have 350 infected people per one million in population. By comparison, China is at 56 people per one million. In the US, in real time, we’re at nine people per million. So back to your point about generally only the sick being tested...
It’s not entirely the case that only those who show symptoms are tested – for example, President Trump was tested without symptoms – but it is the norm. As the Coronavirus Task Force has pointed out – worldwide only about 4% of those who are ill with respiratory illnesses and are tested have had COVID-19. In the United States that’s pacing only around 2%. The point is this – yes, it’s possible that some people could be carrying it without meaningful symptoms and thus aren’t tested, however if a low single-digit percentage of those who are ill and are tested are positive, the percentage who show no symptoms but are infected is likely a microscopic percentage. I wouldn’t read too much into that possibility at this point. The bigger threat appears to be the ability for the virus to live on objects with up to three days and in the air for three hours.
But in terms of sample sizes generally, we have large enough scale in the top ten countries around the world to have a pretty good idea of what the threat looks like and which countries are hardest hit. If you adjust for population, Italy, Switzerland and Norway are the three countries with the highest concentration of cases. It’s a truism in life that we don’t know what we don’t know but for comparison’s sake a phase three trial for an FDA approved drug or treatment ranges from 300 people to 3,000. Right now, what we do know with ten weeks of data, over a million tests being conducted, and well over 100,000 cases we can study, is considerable and far greater than what’s required to have comprehensive scientific understanding.