Most mutations do not affect virus activity: Expert
With more than 500,000 new cases of Covid-19 being recorded worldwide every day and many millions of active cases, the coronavirus has likely undergone thousands of mutations by now, said Professor Dale Fisher, a senior infectious diseases expert at National University Hospital.
But unlike the more infectious strains recently seen in Britain and South Africa, the vast majority of mutations do not have any effect on the activity of the virus, he said yesterday.
Speaking on The Straits Times' daily talk show, The Big Story, Prof Fisher said virus mutations "can go in any of several ways".
In the case of the new strains, a change of the spike protein structure in the virus made it more transmissible by an estimated 50 per cent compared with previous known strains. But future variations could also become less transmissible and cause either more serious or less serious disease.
Professor Alex Cook, vice-dean of research at National University of Singapore's Saw Swee Hock School of Public Health, said the infectiousness of a virus is measured by the reproduction number R0 (R-naught), or the average number of new infections generated by each case.
The R0 of Sars-CoV-2, the coronavirus that causes Covid-19, is hard to calculate accurately as it has never been left uncontrolled, noted Prof Cook.
Experts, however, estimate that it is between two and 2.5. This means each new infected person passes the virus on to two to 2.5 others on average, and those with the new strains would pass it on to even more people.
A more infectious strain means a smaller dose of the virus will be enough to cause disease, said Prof Fisher.
"Maybe if you're being exposed to a positive case, you don't have to be exposed for as long (to catch it)."
But existing measures such as mask wearing and hand hygiene will still be key to fighting the virus, even if they are less effective against the new strains, he said.
"The bottom line is we just have to be a lot more vigilant," he added.