More than 370,000 people around the world have died from Covid-19 and the toll is mounting.
Experts believe for now that the disease will be around for some time yet, unlike the severe acute respiratory syndrome (Sars) which fizzled out in about a year.
"If it were as severe as Sars, it would be much more controllable, and far fewer people (in absolute numbers) would have died and be yet to die," said Associate Professor Alex Cook, vice-dean of research at the National University of Singapore's Saw Swee Hock School of Public Health.
"Covid-19 is possibly at the worst point on the severity spectrum: mild enough that it can still spread like a cold or flu, but severe enough that it kills a substantial number of people."
Sars had a fatality rate of about 10 per cent - calculated by taking the number of deaths over infections - while Covid-19's thus far has been less than 6 per cent.
The fatality rate refers to how likely it is that an infected person dies.
One needs to be circumspect, however, about the Covid-19 figures amid an ongoing pandemic because they may not be accurate.
Experts say many countries are still struggling to cope and there remains a lag time in the reporting of infections as well as deaths.
Experts noted that, for instance, some deaths might have been missed and put down to other causes while infection numbers depended on how well countries could detect cases.
The fatality rate also differs considerably by age group. Early data shows those above 60 have a much higher rate of at least 10 per cent or up to 20 per cent, said Prof Cook's colleague, Professor Teo Yik Ying, who is the dean of the school.
The numbers also do not give a full picture of the situation on the ground. "The apparently low mortality rate masks the fact that certain groups, including those with underlying health conditions, are more susceptible to complications and deaths," Prof Teo said.
These people usually require high dependency care or intensive care.
But as the world learns more about the "smart" coronavirus, which causes Covid-19, the fatality rates tell only a small part of the story, said Associate Professor Josip Car, director of the Centre for Population Health Sciences at Nanyang Technological University's Lee Kong Chian School of Medicine.
"We must weigh how contagious the virus is, how there are different incubation and asymptomatic durations for different people."
Professor Shiv Pillai, a medicine and health sciences and technology professor at Harvard Medical School, said diseases like Sars and Mers (Middle East respiratory syndrome) were spread by symptomatic people, allowing for easy contact tracing and for Sars to be snuffed out.
"New Zealand, Singapore and South Korea have shown that early action can perhaps do the same with Covid-19. But this falls apart once asymptomatic people start emerging from elsewhere. It can be controlled only with tremendous vigilance."
Viruses like Sars, Mers and Covid-19 are unlikely to trigger any form of durable immunity and all it takes is just one infected person at a rock concert or a religious gathering to spark off huge clusters of infection, Prof Pillai said.
UNIQUE PANDEMIC
In the early days of Covid-19, many scientists and governments worldwide turned to experiences and data from past outbreaks to get a handle on how this one would play out. With so much more learnt today, experts say Covid-19 remains unique in its own ways.
"Cross-pandemic comparisons are useful in telling us which groups are more vulnerable and how our solutions can be adjusted accordingly," Prof Car said.
Yet, there are still important questions left unanswered, such as Covid-19's long-term effects even after the virus is no longer in the body and how to keep safe without circuit breaker measures, Prof Car added.
"These specifics are important on how to manage the virus daily as each disease has its own unique trajectory of development."
Prof Teo noted that comparisons are still useful in providing an understanding of the scale and impact of a virus but will not be as operationally relevant though countries with previous experiences with Sars and Mers seem better prepared.
"H1N1 may probably be a good gauge of Covid-19's scale but mortality will far exceed it... H1N1 didn't result in a global lockdown and subsequent impact to economies and livelihoods, like what Covid-19 did," he added.
Prof Cook noted: "Though useful, we shouldn't over-depend on past lessons since the epidemiology is quite different... That's why we could control Sars but globally we're having much more difficulty controlling Covid-19."
Describing the pandemic as the biggest crisis for the current generation, infectious disease expert Annelies Wilder-Smith from the Lee Kong Chian School of Medicine noted the lack of tools at the moment to deal with it other than those that also wreak economic havoc.
"Governments that did not react promptly are now suffering the most... Singapore has done very well, not just in social distancing, but also active case detection and isolation, contact tracing and quarantine."
