Who Can Spread COVID19
Who Can Spread COVID19
As I watched the news last night it was clear to me the announcement being covered from WHO was a big deal. What the news coverage stated was that Asymptomatic carriers were not spreading COVID19 disease.
Wow. That’s a big deal because if that is true then our path to preventing spread potentially got easier. If you are asymptomatic and have COID19 we don’t need to worry about you. So screen everyone for symptoms (and signs) and prevent anyone who has any of the recognized symptoms of COVID19 from mixing with others placing them in self-isolation for monitoring for 14 days
I spent the morning investigating the claim and it was (as usual) a lot more nuanced than was publicized by the media
Current Status
First Let get to the Important point
As for 11:20 ET
But prior to receiving this news, I had already done some research on what they said in their paper: Advice on the use of masks in the context of COVID-19 (updated Jun 5, 2020)
Comprehensive studies on transmission from asymptomatic individuals are difficult to conduct, but the available evidence from contact tracing reported by Member States suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms. They cite several studies where asymptomatic individuals did not transmit the virus
In Maria Van Kerkhove twitter feed there was two tweets that highlighted their position
https://twitter.com/mvankerkhove/status/1270081492908216320?s=20
and the follow up (2/2)
2/2 … on transmission from asymptomatic individuals are difficult to conduct, but the available evidence from contact tracing reported by Member States suggests that asymptomatically-infected individuals are much less likely to transmit the virus than those who develop symptoms
— Maria Van Kerkhove (@mvankerkhove) June 8, 2020
But There’s More
The Annals Article published Jun 3, 2020: Prevalence of Asymptomatic SARS-CoV-2 Infection was a review of available (substantial) evidence on asymptomatic SARS-CoV-2 infection.
Asymptomatic persons seem to account for approximately 40% to 45% of SARS-CoV-2 infections, and they can transmit the virus to others for an extended period, perhaps longer than 14 days.
They also note that asymptomatic may not mean “absence of harm”
The absence of COVID-19 symptoms in persons infected with SARS-CoV-2 might not necessarily imply an absence of harm. More research is needed to determine the significance of subclinical lung changes visible on computed tomography scans.
What Does it All Mean
Even absent the retraction this news was not the slam dunk it was made out to be. Yes asymptomatic carriers *may* be less likely to spread but that data is not certain and as WHO says themselves
Comprehensive studies on transmission from asymptomatic individuals are difficult to conduct
There is still some level of asymptomatic and presymptomatic spread and data suggests that asymptomatic persons are still able to transmit and being asymptomatic might not necessarily imply the absence of harm. Until we understand more of the epidemiology of the disease and are able to carry out more accurate and complete population testing our guidance should remain cautious
So even if asymptomatic patients are less likely to spread, the data re-affirms the current guidance of focusing on clinical screening of employees, students, and visitors to identify those that are symptomatic earlier and self-isolating and monitoring to prevent spread to others, and testing where we can with accurate tests.
Meanwhile, there remains much work to be done on the detailed epidemiology of the disease – for that to happen we need a lot more accurate testing to be available
