Covid-19 is the third coronavirus to jump from animals to humans, but it will not be the last, warns Professor Wang Linfa, director of the Programme in Emerging Infectious Diseases at Duke-NUS Medical School.
The first two were the severe acute respiratory syndrome (Sars) in 2003 and the Middle East respiratory syndrome (Mers) in 2012.
Prof Wang had previously warned in December 2013, after Mers emerged in Saudi Arabia, of another jump of coronavirus from animals to humans within a decade.
His prediction has proven correct with the emergence of Covid-19.
Speaking at the Covid-19: Biomedical Insights Into An Evolving Epidemic webinar organised by the National University of Singapore last night, he again sent out a warning.
He said it is almost certain that another coronavirus will jump species within the decade. The only question is when and how bad it will be.
Prof Wang said: "Coronavirus spillover is definitely going to happen. The question is when? The other uncertainty is whether it will be a big or small outbreak."
Mers does not spread as easily, but has a high mortality rate of one in three. Sars spread more easily with a mortality of 10 per cent. Covid-19 spreads easily, but the fatality rate ranges from about 1 per cent in some countries to more than 10 per cent in others.
Aside from another new coronavirus outbreak, there is also a fear among scientists that Sars-CoV-2, the virus that causes Covid-19, may move from humans to animals - and later jump back to humans.
On the huge outbreak in South America - Brazil alone has 1.6 million people infected with Covid-19 - Prof Wang said: "We have bats everywhere. There are so many bats in the Amazon forest."
If we are really unfortunate, he said, the coronavirus would jump to the bats there and bats can carry the virus without symptoms.
"From time to time, it will spillover to other animals and to humans," he said.
Scientists are seriously examining the risk of bats being "unnatural reservoirs" of the coronavirus.
The other speaker last night was Associate Professor Alex Cook, vice-dean of research at the NUS Saw Swee Hock School of Public Health.
He said the actual number of people infected globally is probably about 10 times the reported number. He asked: "How can we know how many people when some don't show symptoms?"
The only way to know is through serology tests to find out who has the antibodies against Covid-19.
He also said that the higher number of community cases in Singapore may not really reflect a higher rate of infection, but could be because more testing is being done now, so many more people are being picked up.
Yesterday, the Ministry of Health reported 183 new Covid-19 infections, including 23 community cases.