Masks Are Important but No Cure-All: Prof. Tells of Way to Slow Covid Spread

Ben Cowling of the University of Hong Kong discusses what's known among doctors as shortening the 'serial interval distribution.'
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When is comes to slowing the spread of Covid-19, researchers have documented a simple method that involved no drugs or other advanced medicine.

It's called shortening the "serial interval distribution" -- which is essentially the window of time between one infected person showing symptoms and the person whom he goes on to infect showing symptoms.

"For example, if person A infects person B, the serial interval is the time between symptom onset of person A and symptom onset of person B," wrote researchers at the University of Hong Kong's school of medicine, who in collaboration with other universities and the World Health Organization, recently published an article in the journal Science that showed the importance of testing and isolating patients.

In the study, the research team found that by using public health measures for just a month's time, the mean serial intervals of Covid-19 could be cut to about two and a half days from nearly eight days -- which could reduce the spread of infection. 

To find out more about the research, TheStreet spoke with Ben Cowling, a professor at the Hong Kong University School of Public Health, by email over the weekend.

Following is a lightly edited version of the interview.

TheStreet: It sounds like from this work that one tool that can be used to contain the coronavirus outbreak is shortening the "serial interval" time period. 

Cowling: Identifying and isolating infected persons as soon as possible after symptom onset (or even before symptom onset) is a great strategy to stop Covid-19 from spreading. If we achieve that, one consequence will be a reduction in the 'serial interval distribution,' because we prevent the longer serial intervals from occurring.

TheStreet: What are some of the main ways that shortening this time period of infectiousness can be accomplished?

Cowling: Find and isolate a high proportion of all infected persons, as quickly as possible.

TheStreet: What about mask wearing?

CowlingMask wearing would certainly help, but we have seen in Hong Kong that universal use of masks is not sufficient to stop Covid-19 transmission in the community. Masks work, but we can't rely on masks, we need additional public health measures, as well as masks.

TheStreet:  What do you think other countries like the U.S. could learn from this, as it sees the virus rage on?

Cowling: Encourage people to take Covid-19 more seriously. Self isolate and seek testing even with mild symptoms. 

TheStreet: Do you think it's reasonable for a country like the U.S. ... to get a handle on the outbreak at this point?

Cowling: I think public health measures will oscillate between tighter and more relaxed modes in the coming six-12 months. When numbers are lower, measures will relax. When numbers increase, measures will tighten.... But I don't think transmission will ever go back down to zero in the US.