As the COVID-19 pandemic began to sweep the globe in early 2020, Singapore was immediately on the alert, having learned from previous experiences with SARS, H1N1 and Zika. The Lion City is a major Southeast Asian travel hub, and with a local population of over 5.7 million people in a high-density urban setting, was mindful of the impact of a potential pandemic.
Decision-makers had to deploy countermeasures to contain the spread of the coronavirus quickly. However, at the time, COVID-19 was an invisible enemy; relatively little was known about the nature of viral transmission and how best to protect the wider community from a potentially devastating outbreak.
In a bid to fill in the blanks, the Singapore 2019 Novel Coronavirus Outbreak Research Team set to work, assessing the settings and activities linked to spikes in COVID-19 transmission. Their study, published in the medical journal The Lancet, describes the team’s observations on three outbreak clusters that originated from a tour group from China, a corporate event and a church.
Sebastian Maurer-Stroh, Deputy Executive Director of Research at A*STAR’s Bioinformatics Institute (BII), was among a multidisciplinary team of scientists, clinicians, bioinformaticians and epidemiologists involved in the study.
Using a combination of epidemiological and clinical data as well as field interviews, the work provided much-needed answers for how surveillance and contract tracing are vital in curtailing the spread of the virus.
The dynamics of COVID-19 transmission within the spotlighted clusters revealed some interesting findings: of the 36 individuals who tested positive for COVID-19, the transmission of the virus was, in most cases, linked to close contact with an infected individual, such as people living in the same household. Prolonged contact with international travelers, at events such as conferences, also put individuals at a higher risk of infection.
Indirect transmission, through sharing food or touching common surfaces was found to also be a possible route. To mitigate the virus from spreading this way, the authors call for public health messages that stress the importance of proper hand hygiene and social distancing.
Lessons learned from the local clusters indicate that transmission tracking is key. “It is also important for countries to do active case-finding among close contacts of affected individuals, including contacts with mild symptoms, to contain clusters and stop them from spreading,” the authors write.
They also called for further studies to address how the virus is spread by individuals who display no symptoms, which remains a grey zone for epidemiologists. “Although there is interest in asymptomatic transmission, we are unable to address this point in our study, and further studies should be done to better understand disease transmissibility of asymptomatic cases,” the authors write.
The A*STAR-affiliated researcher contributing to this research is from the Bioinformatics Institute (BII).