Commentary: The ways in which the COVID-19 pandemic could unfold
The COVID-19 situation has seen large outbreaks, and is now a pandemic. There are some scenarios as to how this will play out, say Dr Jyoti Somani and Professor Paul Ananth Tambyah.
SINGAPORE: The COVID-19 outbreak has gone global, infecting more than 100,000 people in all continents across the world, except Antarctica.
The World Health Organization (WHO) has now declared this a pandemic to galvanise the world to fight the SARS CoV2 virus which causes COVID-19 disease.
This declaration has had a significant economic impact but it will hopefully succeed in mobilising resources to contain the rapid rise in cases seen globally.
The WHO has also said that this is the first pandemic to be caused by a coronavirus but it will also be the first pandemic that can be controlled.
It is possible that the rapid rise in cases we are now seeing in many countries is the result of infections in highly affected countries reaching a critical point. It may also be a result of the successful detection of infections in countries which have just ramped up testing. In both situations, activating resources will be critical.
COVID-19 cases could also possibly have been missed early in the outbreak, given that its symptoms are similar to influenza and since the early part of the outbreak coincided with the flu season in the northern hemisphere.
Researchers at the University of Washington concluded last week the virus may have been circulating for weeks in the US, after comparing genetic samples of a recent case from a nursing facility in Seattle where there have been a number of deaths, with that from the first US COVID-19 case identified in a traveller in January.
Other possible explanations for that finding include an unusually long incubation period but that would be harder to prove.
A recent case in Singapore also illustrates the importance of recognising false-positive dengue rapid test results in patients with COVID-19.
TWO TRAJECTORIES THE GLOBAL SPREAD COULD TAKE
The good news? Like SARS, the vast majority of patients with COVID-19 will experience a mild illness. A small proportion, about one in 8 to 10, will require intensive care, and some may not survive.
With SARS, testing only became available weeks after the outbreak began, meaning that many mild cases early on were missed, inflating the fatality rate.
The other big difference between SARS and COVID-19, especially in countries previously affected by SARS, is the high degree of healthcare worker protection, which may mean lower rates of infections in medical professionals working on the frontlines.
The bad news? There are two possible scenarios we foresee going forward.
In these, it is important to keep in mind that the extent of the global outbreak in the following months will depend on many key factors that can be shaped, including public health responses, the developments in rapid testing, demonstration of effective treatments and potentially the roll-out of a vaccine.
In the first scenario, the epidemic slows down in the northern hemisphere as it starts to warm up. Even now, the countries with high chains of transmission are those where the temperature remains in the 10 to 15 degrees Celsius range and below - South Korea, Italy, Iran and other European countries, as well as the northeast and northwest of the US.
While many tropical countries have had some cases, so far, there has not been widespread community transmission so far, perhaps because the higher humidity and warmer weather may be preventing rampant spread.
While the virus might disappear altogether in the northern summer like SARS, there is also the risk that, similar to the influenza pandemics of 1918, 1957 and 1968, the COVID-19 outbreak may slow down during the northern hemisphere summer season, but may return in a second wave in October or November when it gets cold again.
READ: Commentary: Hot and humid weather may end the novel coronavirus – as well as the development of a vaccine
The second possible scenario is that the COVID-19 disease may turn out not to be sensitive to temperatures, in which case, the spread of infection will continue worldwide for months, at least until herd immunity develops in communities.
Scientists are speculating what proportion of the population will get infected in that case. For H1N1 in 2009, we know that figure was around a quarter of the population after the first wave of infections.
We also know that COVID-19 is more severe than influenza so the impact on healthcare systems, especially in low and middle-income countries can be significant if such large proportions of the population are infected.
THREE SCENARIOS FOR LARGE OUTBREAKS
While the vast majority of patients with COVID-19 do not spread the infection at all and some spread the infection to only a couple of family members, there are some unique situations that have resulted in much more extensive spread – these have been dubbed “super spreading events”.
One of the first super-spreading events was the Diamond Princess cruise ship that remained off the coast of Japan for 14 days. Eventually, a total of 696 persons were infected out of 3,711 persons onboard, as well as some public health officers.
Cruise ships are already well known for outbreaks of other highly infectious pathogens including the norovirus (known locally as “stomach flu”) and influenza for a variety of reasons, including the close quarters, risk of environmental contamination and generally older population.
READ: Commentary: Why Japan’s move to close schools during COVID-19 outbreak upset many – and not just parents
Cruise ships, including Costa Fortuna which berthed at Singapore this week, will continue to be watched carefully.
Second, larger gatherings where people huddle together, sing or share food, can potentially lend themselves to huge outbreaks, if there happens to be someone shedding large quantities of virus.
The huge and rapid outbreak in South Korea among members of a religious group, which has over 200,000 members, accounted for more than half of the over 7,000 cases of COVID-19 infections in the country.
Nursing homes have elderly patients with many comorbid conditions. Many live in close quarters with common staff and caretakers.
Thus, there is always a risk of healthcare acquired infections which can spread rapidly, including influenza and other respiratory viruses, norovirus and other gastrointestinal illnesses. The COVID-19 outbreak has led to new screening, visiting and other precautionary measures in many nursing homes and assisted living facilities in the US.
The fear remains that if such incidents occur in other long-term care facilities across the world, the toll on elderly or disabled people from COVID-19 will be significant.
FOCUS ON MEDICAL DEVELOPMENTS, RELOOKING LARGE GATHERINGS AND ENCOURAGING TESTING
Three areas of focus lie ahead in the fight against COVID-19.
First, scientists are already working on treatments. There are studies now enrolling patients (with some starting this week in Singapore) to see if any of the known and newer anti-viral drugs will be effective.
In addition, newer and more effective tests are being developed, including blood tests that can tell whether a person has already been infected such as the one used by Duke-NUS to establish the link between the two church clusters in Singapore.
READ: Commentary: Developing affordable, accurate test kits for COVID-19 one of the biggest challenge this outbreak
Second, the need to cancel large gatherings and the impact of social distancing can be better examined once more reliable testing on a population basis can be done.
Third, while countries focus on containing the virus, the key is still in identifying every case. In addition to broadening testing, providing free treatment or compensation for those on medical leave is critical to encourage people to get tested and treated, to ensure that they will not be penalised by their employers, or be deterred by the thought of potential financial difficulties.
This is especially challenging in low-income countries and low-income households with sole bread-winners.
Difficult decisions will have to be made while we wait for the scientific consensus or the development of new treatments and vaccines.
Public health authorities must decide when to move from containment, which requires doing costly and labour-intensive contact tracing for every case, to mitigation, where we focus on those who are most vulnerable to prevent complications while keeping track of the situation in the broader community.
With the concerted global effort of clinicians, scientists, public health professionals and the public, there is a good chance, we will succeed in limiting suffering and deaths from COVID-19.
Assistant Professor Jyoti Somani works at the Department of Medicine at the Yong Loo Lin School of Medicine at NUS. Professor Paul Ananth Tambyah is President of the Asia Pacific Society of Clinical Microbiology and Infection and works at the same school.