How Social distancing be effective to reduce spread of coronavirus?

Singapore, Mar 24: A combined approach of physical distancing -- comprising quarantine, school closure, and workplace measures -- is most effective at reducing the number of novel coronavirus cases compared with many other interventions, according to a study published on Tuesday.

The modelling study conducted in a simulated Singapore setting estimated that quarantine plus workplace measures, while less effective than the combined approach, presented the next best option for reducing SARS-CoV-2 cases.

This was followed by quarantine plus school closure, and then quarantine only, according to the researchers. All intervention scenarios were more effective at reducing cases than no intervention, they said.

The study, published in The Lancet Infectious Diseases journal, is the first of its kind to investigate these options for early intervention in Singapore using simulation. Despite heightened surveillance and isolation of individuals suspected to have COVID-19 and confirmed cases, the risk is ongoing, with the number of cases continuing to increase in Singapore, the researchers said.

Schools have not been closed, and workplace distancing is recommended, but it is not national policy as yet, they said. The study found that the combined approach could prevent a national outbreak at relatively low levels of infectivity.

However, at higher infectivity scenarios outbreak prevention becomes considerably more challenging because although effective at reducing infections, transmission events still occur.

"The results of this study provide policy makers in Singapore and other countries with evidence to begin the implementation of enhanced outbreak control measures that could mitigate or reduce local transmission rates if deployed effectively and in a timely manner," said Alex R Cook, from National University of Singapore.

To assess the potential impact of interventions on outbreak size, should local containment fail, the researchers developed an individual-based influenza epidemic simulation model. The study accounted for demography, individual movement, and social contact rates in workplaces, schools, and homes, to estimate the likelihood of human-to-human transmission of SARS-CoV-2.

Using this model, the researchers estimated the cumulative number of SARS-CoV-2 infections at 80 days, after detection of 100 cases of community transmission. Compared with the baseline scenario, the combined intervention was the most effective, reducing the estimated median number of infections by 99.3 per cent when basic reproductive value (R0) was 1.5 (resulting in an estimated 1,800 cases).

However, the researchers noted that at higher infectivity scenarios, outbreak prevention becomes considerably more challenging.

"If the preventive effect of these interventions reduces considerably due to higher asymptomatic proportions, more pressure will be placed on the quarantining and treatment of infected individuals, which could become unfeasible when the number of infected individuals exceeds the capacity of health-care facilities.

"At higher asymptomatic rates, public education and case management become increasingly important, with a need to develop vaccines and existing drug therapies," Cook added.