30th JANUARY 2020
It has been just over 4 weeks since the announcement of an unusual pneumonia affecting numerous residents of Wuhan. The cases were linked to the Huanan wholesale seafood market in Wuhan, Hubei province in China. Approximately 10 days later, a novel betaCoronavirus was identified as the pathogen and the genome was released to the scientific community. It has since been named 2019 novel Coronavirus (2019-nCoV).
In the past 10 days until January 30th 2019, the number of human infections have exploded, with China reporting 7711 confirmed cases, 170 deaths (as of January 30th). Wuhan, the epicentre of the epidemic and numerous other cities in Hubei with an estimated population of almost 58 million have been in partial or full lockdown since January 23rd 2020. This large scale quarantining of multiple cities marks an unprecedented public health response to 2019-nCoV epidemic.
As a result of global air travel, at least 18 countries outside of China have reported more than 100 cases of 2019-nCoV infection. In Singapore, we have 10 cases identified as of January 29th 2020 and a multi-ministry task force has been convened. Four weeks on, it is time to take stock of the situation and review what we know and what we should be planning for.
What we know:
Characteristics of the Virus. The genomic sequence of 2019-nCoV is 75-80% identical to the SAR-CoV and even more closely related to several bat coronaviruses. It propagates well in human airway epithelial cell cultures and appears that it uses the human angiotensin-converting enzyme 2 receptor (hACE2) to enter the lungs. This is the same receptor used by SARS-CoV and partially explains why 2019-nCoV and SARS-CoV cause pneumonia. There is suggestion that 2019-nCoV may have continued to mutate and adapt in the past few weeks to infect humans more easily. Coronaviridae have error prone RNA dependent RNA polymerases making mutations and recombinant events frequent. It is likely that 2019-nCoV will behave more like SARS-CoV than other Coronaviridae. Recent reports also point towards infected patients with mild or minimal symptoms and who are “infectious” and contribute to ongoing transmission of this infection.
Sustained human and human transmission is ongoing, with family clusters in China identified early in the epidemic. Reports from Vietnam, Germany, Taiwan and Japan have identified infected persons who have not travelled to China but who have had contact with persons from China who were subsequently identified to have 2019nCoV.
2019-nCoV is most likely transmitted by droplets. Although anti-coronaviral therapies are still in development, public health measures such as strict isolation of infected cases, quarantining of contacts, strict infection prevention and control measures will be critical in controlling the 2019-nCoV epidemic. It is likely that there is high variability in the number of new infections generated by each infectious individual. Niall Ferguson’s group at the WHO Collaborating Centre for Infectious Disease Modelling, Imperial College, have estimated that the basic reproduction number was 2.6. That is, each infectious case will “on average” transmit to 2.6 other persons. Whether transmission continues at this rate will depend on the intensive control effort underway in Wuhan and across China. When the reproduction rate is <1, the epidemic will slowly end.
The epidemic is evolving and the situation is fluid. It is likely that we have not seen the peak of the epidemic.
What we do not know.
There are still many unknowns and they include the following:
- Incubation period: The current working period has been “up to 14 days”. There have been limited studies that suggest that a more accurate range is 3-6 days.
- Infectivity: health authorities disagree if patients during the incubation period are “infectious”. There are reports that patients with mild symptoms may be infectious.
- The animal reservoir. Because of its close similarity to several bat associated coronavirus, bats are postulated to be the likely primary reservoir. Whether there is another animal reservoir before it jumped species to human infection is under investigation.
Spare a thought for the residents of Wuhan and Hubei Province!
Patients with infections have always faced discrimination. The residents in Wuhan and Hubei province who are at the epicentre of the 2019-nCoV epidemic are best described as “victims” and continue to face scrutiny and restrictions by many countries and also within China. They face the ongoing widespread threat of community transmission of 2019-nCoV where they live and also have to deal with the travel restrictions imposed because of the “lockdown”. We hope that this epidemic will end soon and normalcy will return.
The situation in Singapore
There are 10 confirmed cases of 2019-nCoV in Singapore as of January 29th 2020. The reports from MOH state all the infected patients in Singapore are stable and some have started to recover from the illness. All the cases in Singapore had travelled from Wuhan, Hubei. There has been no local transmission of 2019-nCoV and this is most fortunate. Thus, we have the opportunity of using history of travel as the most important factor in screening for patients who are at risk of 2019-nCoV infection.
The 2019-nCoV epidemic is a clear and ongoing global infectious disease threat. We should always “hope for the best but prepare for the worst”.
Dr Lam and Dr Wong
30th January 2020