People have asked me several questions about the implications of the New York Times story reporting that most positive PCR tests for coronavirus are for very low levels of virus, so low that clinically they are not infectious, not do they have an “illness”. This is related to my ramblings in a few posts about what it means to be infected or infectious. Many people have likely been “exposed” to the virus–that is they have inhaled it directly or had it land on them, especially in the face area, and then moved in and inhaled or ingested it. What is now very, very clear, is that for most of those people, probably over 90%, the virus is almost immediately cleared, it never gets a chance to start a serious replication cycle. But if they are tested in the window when there is either viable virus in their upper respiratory tract, or if there are still RNA fragments in that area, which can persist for several days, then depending on the sensitivity of the test readout, they could test positive. The essence of the Times story was that clinicians think these low-level positive results should be ignored–the people aren’t ill and they aren’t infectious; and if you don’t ignore them, you are wasting effort that could be better spent on people with higher levels of virus who are more likely to be or become ill, or who are likely to be infectious.
There are many implications if the Times findings represent an accurate picture of PCR testing across the country, and I would suspect that they do. One is that it validates the notion that not just some, but the vast majority of “cases” are asymptomatic. It also validates the lack of transmission by asymptomatic persons. If clinicians are saying stop worrying about people with such low levels of virus, they are admitting that they aren’t transmitters. And if so many people so easily clear the virus the most logical explanation is an immune response.
This has particular ramifications for children and college age students. We need to know what their test results looked like. I think we can be pretty certain that almost every one of the positives for this group falls into that too low to worry about bucket. So we can stop closing schools just because a student test positive.
But in terms of determining outcome parameters, such as hospitalization rates and death rates, these low-level exposures and case should be counted, they do represent exposures. Otherwise, a pathogen that is easily handled by almost everyone looks like something quite deadly. So, what I think is devastating about this to those who portray this as such an awful epidemic, is that in fact, exposure to the pathogen is an unnoticeable event for almost everyone. It will be fascinating to see if the traditional media follow up on the implications and how politicians and public health officials waffle and weasel around this finding. They can’t blame the source, which is their usual tactic.