New CDC recommendation: no auto testing for contacts without symptoms. "Experts question the revision" in the US. Yet *no testing in the absence of symptoms* has always been our approach to #COVID19 in BC (with important exceptions). Why? Explainer... 1/ https://www.nytimes.com/2020/08/25/world/covid-19-coronavirus.html#link-3ff60f07

Wrapping an answer around points in this NYTimes article: (A) “Models suggest that about half of transmission events can be traced back to the pre-symptomatic stage.” Yes. This is why ALL CONTACTS OF CASES SHOULD ISOLATE REGARDLESS OF TEST RESULTS. 2/

Current tests have limited sensitivity even during symptomatic illness, and lower still pre-Sx. A ‘negative’ test doesn’t mean ‘infection-free.’ 3/

(B) ‘guidelines could be misinterpreted as implying people without symptoms are unable to pass the virus.’ It's also dangerous to imply that contacts with a negative test are unable to transmit! For COVID-19 contacts, A NEGATIVE TEST SHOULD NOT CHANGE THE PLAN TO ISOLATE. 4/

(C) “A more lax approach to testing could delay crucial treatments.” Odd assertion. There are very limited treatments for COVID-19, and instances when they would be used in the absence of symptoms are vanishingly rare. Treatment is not a rationale for testing ASx contacts. 5/

I am not saying that every jurisdiction should test only symptomatic contacts. Our practice in BC requires rapid access to testing and results if a contact develops symptoms... 6/

...It also relies on buy-in for members of the public to isolate if named as a contact. This usually requires that employers support those who must isolate, which unfortunately is not always the case (and less often the case in some places than others). 7/

Regarding the exceptions mentioned above, public health officials may recommend asymptomatic testing in specific circumstances, such as outbreak investigations among people who may be differently able to detect or report symptoms (e.g. many long-term care residents). 8/

If access to tests or turnaround are limited, the conversation changes. Context matters, and the context for testing policies varies by country and certainly by state. All respect to colleagues elsewhere who see value in testing asymptomatic contacts... 9/

...But if you’ve asked why we don’t do this in BC or most of Canada, here is an answer. Details here: http://www.bccdc.ca/Health-Professionals-Site/Documents/COVID19_Testing_Asymptomatic_Individuals.pdf Stay safe! 10/10