The results of a University of Southampton-led study that examined non-pharmaceutical interventions (NPIs) in response to the new coronavirus (SARS-CoV-2) in China have suggested that a range of early, coordinated, and targeted measures are needed to help significantly reduce spread of the virus.

Researchers in the population mapping group WorldPop ran complex modeling, using anonymized data on both human movement and illness onset, to help simulate different outbreak scenarios for cities in mainland China. This allowed them to understand how variations in the timing, level, and combinations of interventions affect speed and transmission of COVID-19 disease.

Shengjie Lai
Shengjie Lai BMed, MMed, PhD
University of Southampton

“To our knowledge, this is the most comprehensive study to date on quantifying the relative effect of different NPIs and their timings for COVID-19 outbreak containment, based on human movement and disease data,” they wrote in a preprint of their work, which has been made available on the medRxiv website, and is titled, “Effect of non-pharmaceutical interventions for containing the COVID-19 outbreak: an observational and modelling study.” Co-corresponding author Shengjie Lai, PhD, further commented, “Our study demonstrates how important it is for countries which are facing an imminent outbreak to proactively plan a coordinated response which swiftly tackles the spread of the disease on a number of fronts. We also show that China’s comprehensive response, in a relatively short period, greatly reduced the potential health impact of the outbreak.”

To carry out their study the researchers analyzed data from 15 studies that investigated the potential effects of traveler screening, the lockdown in Wuhan travel restrictions, and contact tracing in China or other countries. “We built a travel network-based susceptible-exposed-infectious-removed (SEIR) model to simulate the outbreak across cities in mainland China,” they wrote. “We used epidemiological parameters estimated for the early stage of outbreak in Wuhan to parameterize the transmission before NPIs were implemented. To quantify the relative effect of various NPIs, daily changes of delay from illness onset to the first reported case in each county were used as a proxy for the improvement of case identification and isolation across the outbreak.” Historical and near-real time data were used to derive the degree of travel restrictions and contact reductions in China.

From their collected data the researchers estimated that by the end of February 2020 there were a total of 114,325 COVID-19 cases in China. Their analyses showed that the NPIs—such as early detection, isolation of cases, travel restrictions and cordon sanitaire—
the number of infected people would have been 67 times larger than that which actually occurred.

The findings also indicated that if interventions in the country had been conducted one week, two weeks, or three weeks earlier, the number of cases could have been reduced by 66%, 86% and 95%, respectively, which would have significantly limited geographical spread of the disease. On the other hand, if NPIs had been implemented one week, two weeks, or three weeks later than they actually were, the number of cases may have shown a 3-fold, 7-fold, or 18-fold increase, respectively, across China.

The researchers concluded that their results do show how NPIs, inter-city travel restrictions, social distancing and contact reductions, as well as early case detection and isolations, have helped to substantially reduce COVID-19 transmission across China. The effectiveness of different interventions did vary, they also noted. Improved disease detection, isolation of cases and social distancing (for example, the cancellation of large public events, working from home and school closures) are likely to have had a far greater positive impact on containment than travel restrictions. “The early detection and isolation of cases was estimated to prevent more infections than travel restrictions and contact reductions, but integrated NPIs would achieve the strongest and most rapid effect,” they wrote.

The authors also suggested that social distancing should be continued for the next few months in China to prevent case numbers increasing again after the lifting of travel restrictions in late February. They believe that their findings will help to contribute to improved understanding of how integrated NPI measures can impact on COVID-19 containment and will help to tailoring control strategies across contexts. “Given that effective COVID-19-specific pharmaceutical interventions and vaccines are not expected to be available for months, NPIs are essential components of the public health response to the ongoing outbreaks,” they concluded. “Considering the narrowing window of opportunity around the world, early and integrated NPI strategies should be prepared, deployed and adjusted to maximize the benefits of these interventions for containing COVID-19 spread.”

Co-author Andy Tatem, PhD, director of the University of Southampton’s WorldPop group, stated, “We have a narrow window of opportunity globally to respond to this disease and given effective drugs and vaccines are not expected for months, we need to be smart about how we target it using non-drug-related interventions. Our findings significantly contribute to an improved understanding of how best to implement measures and tailor them to conditions in different regions of the world. We are now focussed on adapting this work to new settings beyond China to support response efforts. Different countries may need different approaches, but we aim to help them make informed decisions on how best to put interventions in place.”

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