Covid-19 is the third pandemic of the 21st century. It calls for a new
strategy, combining both containment and mitigation, to address its unique
combination of severity and transmissibility.
By Associate Professor Lim Poh Lian, Senior Consultant at NCID
In her books, "The Coming Plague" and "Betrayal of Trust", Pulitzer Prize winning author, Laurie Garrett makes the case that "preparedness demands understanding".
The world is now two months into the Covid-19 epidemic, which was elevated into the status of a pandemic just this week. On Wednesday, the World Health Organisation declared the outbreak a pandemic, which it defines as worldwide spread of a new disease for which most people do not have immunity.
So what do we know of Covid-19?
We know this infection to be caused by Sars coronavirus 2 (SARS-CoV-2), a sibling of the Sars virus that caused the first pandemic of the 21st century in 2003.
For infectious disease physicians who fight outbreaks, discovering a new virus is like an astronomer discovering a new black hole or dwarf star.
We need to understand how the virus infects people, how long before it causes symptoms, how fast it spreads, how lethal it is, how long it survives in the environment, who is infectious, for how long and from which samples, whether people can get re-infected, how to make a vaccine that protects people, and what treatments are safe and effective.
But while all these questions are being asked and answered by research studies, we don't have the luxury of waiting for perfect answers. Outbreaks require health authorities and governments to make judgement calls based on incomplete information amid rapidly changing circumstances, and to make the right call.
A week is an eon in outbreak time. Within a week, South Korea, Italy and Iran saw dramatic surges, but the truth is, this could happen in any country.
Covid-19 and SARS compared
What do we know so far of CovidD-19 compared to SARS?
It is milder but more infectious than Sars. Covid-19 will be more difficult to control than SARS precisely because a larger proportion of patients have mild disease and may not even realise they are infected.
Coughs and sore throats are common; we cannot possibly test every upper respiratory tract infection (URTI) in Singapore. Persons with mild disease are more likely to continue with their daily activities and expose others, unless they are diligent about staying home on medical leave to prevent onward spread.
Our experience in Singapore shows that three quarters of Covid-19 patients have fever, so screening out fevers is useful, as long as we recognise that absence of fever does not preclude Covid-19 infection. While we worry about the spread of infection from patients without any symptoms at all, the truth is such asymptomatic transmissions are rare. Most patients get infected from someone with symptoms, with whom they have been in close contact.
Covid-19 is far more serious than a "bad flu"
Friends have asked me if Covid-19 is just a bad flu, and whether we are over-reacting. That is a fair question, especially after the 2009 H1N1 influenza pandemic, which started with a bang and fizzled out.
Why did the World Health Organisation and the world over-react to that? We were watching and waiting for the "Big One" to strike again, the 1918 pandemic which killed between 20 – 50 million people because its fatality rate was 2%.
When the 2009 H1N1 outbreak started in Mexico, its fatality rate was initially reported at 2 per cent. Everyone was still worried about H5N1 influenza when it emerged in Southeast Asia, so everyone thought, "This is it, this is the Big One." In the end the fatality rate of H1N1 was 0.02 per cent.
Why did health authorities overestimate the fatality rate of H1N1 influenza in 2009?
At the start of any outbreak, it is the sickest patients who get tested. The fatality rate is the number of deaths divided by the number of confirmed infections, so a small denominator makes the outbreak look more frightening at first. As more people get tested who have milder disease, death rates go down and everyone heaves a big sigh of relief.
Covid-19 fatality rates
We have not seen this drop in Covid-19 fatality because serological surveys for mild disease have not yet been done. What we do know is that the fatality rate can vary. The 4.1% death rate in Hubei, four-fold higher than the 0.9% death rate in China outside Hubei, may be a result of the outbreak surge overwhelming healthcare systems, or more vulnerable patients getting infected.
In Singapore, we have now diagnosed more than 160 cases over ten weeks, of whom 10 to 15 per cent required intensive care, an experience consistent with published medical reports on cases overseas.
If the total numbers of Covid-19 infections rise sharply and community transmission results in more vulnerable individuals getting infected, there will be many more critically ill patients.
So what can we do about the pandemic?
When we have an epidemic caused by a completely new virus for which we have no vaccines and no proven treatments, old-fashioned outbreak control methods must suffice.
Infectious patients are cared for with proper precautions, exposed persons are quarantined. For 40 years, we stopped Ebola outbreaks this way. The world stopped Sars in 2003 with these public health measures.
We have seen with Sars and Mers (Middle East Respiratory Syndrome) how one person with unsuspected infection can spark an outbreak. Most people do not knowingly seek to infect others.
The key step to a sustainable outbreak response is having access to accurate diagnostic testing to confirm Covid-19 infection, so that patients can stay in isolation until no longer infectious to others.
No one in the world has immunity to SARS-CoV-2 because it is a new virus. By containing Covid-19, we are buying time for the scientific community to develop vaccines and other medical countermeasures to protect us all, from a virus our immune systems have never seen.
We must contain Covid-19 because of its impact on health systems, on lives and on livelihoods.
Uncontrolled spread of Covid-19 in Singapore may lead to loss of confidence by businesses, and entry bans or quarantine for persons coming from Singapore. However, with Covid-19 spreading across the world and likely to go on for months, we must find a way to function and move forward.
To recap: Covid-19 is not SARS and Covid-19 is not influenza.
In the uncharted territory referred to by WHO Director-General Dr Tedros Ghebreyesus, we must craft a new response that combines both containment and mitigation.
This is precisely the approach Singapore has adopted: proactive in diagnostic testing to detect infectious cases, prompt with contact tracing and quarantine of exposed persons, all standard containment measures.
At the same time, we recognise that life must go on because the Covid-19 situation will stretch over months. Singapore takes a whole of society approach. Mindful of the impact on business, social life and psychological wellbeing, we have measures to support businesses, and community efforts to maintain morale among healthcare workers. Direct government-to-citizen communications provide reliable information to facilitate calm, rational decisions. At a time of fear, when it is tempting to lapse into xenophobia, clear statements of what we desire to be as a country help create a positive and cohesive sense of community.
It is possible that Singapore's blended approach of containment and mitigation, with its whole-of-society response, may show the way forward for a world grappling with a Covid-19 pandemic.