ASYMPTOMATIC TRANSMISSION OF COVID-19

One of the distressing things about COVID-19 is you can get it from someone who isn’t sick. Like chicken pox, which is contagious for 2 or 3 days before the rash appears, COVID-19 can be transmitted before the person who has it knows it. That makes the disease very hard to control. Unless everyone is tested, there is no way to know who’s contagious and who is not.

Asymptomatic COVID-19 patients make up between 17-20% of those who test positive. But of all the patients who test positive before having symptoms, 49% go on the develop symptoms. So are the other 51% false positives or is the test overly sensitive and not specific for COVID-19? The latter seems to be the case.

The only way to detect live virus infection is by viral culture. Viral cultures are expensive and take 7 days to get results. Polymerase chain reaction (PCR) tests, done today, give results quickly, but don’t distinguish between live virus and viral RNA. Therefore, persons who test positive may not have active virus and may not be infectious.

The detection of RNA does not mean the person has a contagious virus. It may, but there’s no way to know. Asymptomatic patients who test positive are 3-25 times less likely to be contagious than patients who are symptomatic when they are tested. Viral cultures have determined that contagion begins 1-2 days before and lasts up to 7 days after symptoms begin. The viable period of the COVID-19 virus is short-lived. Transmission of the virus occurs more frequently from persons who are either symptom-free or are just beginning to be sick. They don’t know they have the virus and are not limiting their interaction with contacts. By the time patients develop symptoms, they have already exposed many contacts. Isolation helps from then on, but it’s too late for those already exposed.

“Coughing…may result in far more viral particles being shed than talking and breathing.” The fact is “asymptomatic and presymptomatic people may have more contacts…underlining the importance of hand washing and social distancing measures…”

These facts beg the need for more widespread testing. The only way to stop the spread is to test everyone and isolate every person who tests positive. Viral cultures should be done on all positive results to gauge the frequency of false positive tests. If we tested every single American in one week, and isolated everyone who tested positive, the disease could be controlled. Those who test negative should be re-tested 3 days later. Those positive on the second testing should also isolate for 10 days. That would really shut this down without the economic impact we have seen.

Here’s my plan: We should have a national declaration of a “COVID-19 testing Week.” People are tested in alphabetical order over a 7-day period with results available in less than an hour. You return home knowing whether you need to isolate from others. No one can interact with positive testers unless both use personal protective equipment (PPE). Symptomatic people are protected maximally and hospitalized if necessary. The people who do testing will rotate being replaced by people who test negative twice. After 10 days, those who were isolated are retested. If you’re negative, your life resumes. If you’re still positive, a viral culture is done. You remain isolated until culture results are back. Those results plus your symptom status would determine what happens next; resume normalcy or continue isolation.

This would be a huge task, but if everyone cooperated, it could be done. Prevalence of the disease would take a hit, and contagion would be contained to the degree people cooperated. Asymptomatic spread would be stopped. Testing weeks could occur at whatever interval was necessary until a vaccine is administered to everyone or until no positive tests are found. Asking people to do this would take a monumental public relations blitz. For this to be successful, people would have to grasp the importance of cooperating, and there would need to be consequences for uncooperative folks. This sounds totalitarian, but it’s far less troublesome than “locking down” entire states and killing small businesses like has been done since March.

Reference: Pollock AM, Lancaster J Asymptomatic transmission of covid-19. BMJ 2020;371:m4851.