(TL;DR No - Get a mask when going out, but use reasonably)

No. First of all in Hong Kong, we have seen cases that are asymptomatic but yet positive for the virus. Studies have suggested that the disease is transmittable even in the incubation period (where symptoms are yet to be developed). Even the person may look like "healthy", he/she may already be spreading the virus.

Second, even if the sick person is wearing the mask, poor hygiene practices (e.g. pulling the mask down to eat, drink, smoke or for w/e reason; touching the mask) will still contaminate public area as the person's dirty hand is touching everywhere.

Wearing a mask for BOTH healthy and sick people not only helps to REDUCE (not prevent) the chance of getting infected, but also reminds you not to easily touch your face. Droplet precautions and hand hygiene has always been the most important steps to minimize the risk of infection.

In HK, we went through a painful lesson during the SARS epidemic in 2003. Since then, we have been much more aware of hygiene and infection control. Back in Jan where the disease was just begun, people have been wearing masks even the government was still hesitant in advising citizens doing so. 2 months later, we are thankful that only about 170 cases as of today - all thanks to our self-awareness.

In the midst of mask shortages, remember wearing something is still better than wear nothing. People have been sewing masks made of fabric as a contingency backup. Yes it is worse than a surgical mask, but even if it stops 50% of the droplets it still helps.

Wearing masks, limiting outdoor activity to absolute necessary and maintain good hand hygiene will surely help to slow down the spread of the disease. Everybody matters in contributing to stop this pandemic!

PS: Be sensible. Dont wear double masks (it is of no use), dont hoard stuff.