Can Asymptomatic persons positive for covid-19 transmit disease

I believe we need to act as if they can.

A report from the chief epidemiologist from China's CDC in early March seemed to be reassuring.
Dr. Z.Wu speaking on an online conference on March 6 told the audience that transmission from presymptomatic people is rare and indicated that the  rate was 1-5% among person in close contact with infected patients.

Subsequent reports and consideration of foci of  rapid spread, (e.g. the Boston Biogen conference,the ill- fated cruise of the Diamond princess) suggest presymptomatic transmission may not be rare.

Japanese researchers found 634 of the 3711 passengers on the Diamond Princess tested positive and estimated 17.9 percemt were asymptomatic .

Using data from Tiajin China  Dutch researchers used a mathematical model to estimate from Tiajin  that the proportion of pre-symptomatic transmission was 62% ( 95% CI 50-76 %)

Note- these two analyses give estimates  and not actual proven head counts of instances of spread from person without symptoms

Viral counts are higher in the nose and throat and peak earlier in covid 19 infections than was the case with SARS so that it seems very plausible that a pre-symptomatic person could transmit disease.

 Further, even if the outer bounds of these estimates are still overestimates  the likelihood of pre-symptomatic spread  raises  major questions regarding  some of the current guidelines and  advice from public health experts.

If exposed health care workers are allowed to return to work based on history of no symptoms and there is asymptomatic spread then other workers and patients are at risk.

Early on in the U.S, public health experts discouraged the use of masks by the general public at times with an apparently self contradicting argument that 1) masks don't really work and 2)masks should be reserved for doctors and nurses.

 Of course, Surgical masks are not as effective a N-95 units but since viruses spread by droplets , masks offer some protection. Telling the public  that masks don't work does not seem to be very good advice and that position seems to have largely walked back.

 Early on US public health spokespeople  downplayed possible pre-symptomatic transmission but now that has changed.In fact Dr. Scott Gottlieb said "We know there is asymptomatic spread".Further, in a 3/18/200 tweet he suggested that if the youth who are ignoring efforts to be socially distant they should be required to wear masks"

I believe also that high risk people who for good reason must venture into crowded areas  ( e.g. groceries) should wear masks. I know I am- being at high risk by reason of age.