This Lancet Study has Huge Implications
This study was recently published in the Lancet. The Lancet is one of the oldest and best known medical journals in the world. The authors examined the research, to date, on viral load duration and transmission. They looked at studies on SARS-CoV1, MERS-CoV, and SARS-CoV2.
Looking at the data they found, high viral loads of SARS-CoV1 peaked at days 10-14 from first day of symptom onset. High viral load of MERS-CoV peaked at days 7-10. High viral load of SARS-CoV2 peaks at days 0-5 from the first day of symptom onset. They also found a mean duration of viral RNA shedding of SARS-CoV2 of 17 days and a maximum of 83 days. They found that no study was able to culture live virus from the upper respiratory tract of SARS-CoV2 positive individuals beyond 9 days. They did not find any study that confirms pre-symptomatic viral load peak.
One significant purpose of writing their study was to help influence public policy. To help policy makers understand the science so they can follow it. In this case, how long is someone contagious? Ultimately they believe that due to the short window of contagiousness, early isolation and early testing is very important to slow transmission of the virus in the community.
You Should Still Quarantine if Positive.
But for how long?
What they concluded was that peak viral load occurs from days 0-5 based on the day that your symptoms started. This means that this is the time frame you are most contagious. After day 5 that level of contagiousness drops off. After day 9 it is very likely you are not contagious at all, despite still shedding virus. The issue is for how long should you isolate. From the data, isolation should last no more than ten days from first day you symptoms started.
The clear conclusion is that early isolation makes the most significant difference in reducing transmission. The conundrum is, what happens if you don’t get tested until after your first day of symptoms. Then you don’t get a result for a few days after that. By then, you might test positive but no longer be contagious. Or your period of peak contagiousness has past and you are days away from not being contagious at all. Viral shedding lasting possibly up to 80 days means people can still test positive for a long time but no longer be contagious. It is very likely there are people in home isolation longer than they need to be.
Really how long?
Don’t ask me, I am in no professional position to say for how long. At least I am pretty sure I’m not licensed to tell you how long to quarantine. It is very important to isolate early, immediately after you first notice symptoms. That will make the most difference in reducing transmission. Don’t go to work symptomatic, don’t send your kid to school with symptoms. What are the most common symptoms? Fever, cough, shortness of breath, or loss of smell or taste. Even with atypical symptoms it is important to isolate early until you know for sure with a test.
If you are asked to quarantine for longer than 9 days past your first day of symptoms I would challenge that, be sure to bring your data too. This Lancet study. It’s free to download.