Extending closures in Wuhan likely to delay second wave of Covid-19: Study

Extending school and workplace closures till April, rather than March in the epicentre of the Covid-19 pandemic, the Chinese city of Wuhan, can likely delay a second wave of cases until later in the year, relieving pressure on health services, according to a new study.

The research, published inThe Lancet Public Healthjournal, says the closure of schools and workplaces in Wuhan have reduced the number of Covid-19 cases and substantially delayed the epidemic peak -- giving the health system the time and opportunity to expand and respond.

In the study, researchers, including those fromthe London School of Hygiene & Tropical Medicine in the UK, used mathematical modelling to estimate that by lifting these control measures in March, a second wave of cases may occur in late August.

However, they said,maintaining these restrictions until April, may delay a second peak until October, relieving pressure on the health services in the intervening months.

The scientists also said given the large uncertainties around how many people an individual with the virus is likely to infect, and how long a person is infected on average, the true impact of relaxing physical distancing measures on the ongoing Covid-19 epidemic cannot be precisely predicted.

"The unprecedented measures the city of Wuhan has put in place to reduce social contacts in school and the workplace have helped to control the outbreak", said Kiesha Prem from the London School of Hygiene & Tropical Medicine, who led the research.

"However, the city now needs to be really careful to avoid prematurely lifting physical distancing measures, because that could lead to an earlier secondary peak in cases. But if they relax the restrictions gradually, this is likely to both delay and flatten the peak," Prem said.

When the novel coronavirus (SARS-CoV-2) emerged in Wuhan, China in December 2019, schools and workplace were closed as part of the Lunar New Year holidays, the scientists said.

These closures, they said, were then extended to reduce person-to-person contact and prevent the spread of SARS-CoV-2.

The researchers developed a transmission model to quantify the impact of school and workplace closures using information about how often people of different ages mix with each other in different locations.

They assessed the effects of these measures on bringing the outbreak under control.

Using the latest data on the spread of Covid-19 in Wuhan, and from the rest of China on the number of contacts per day by age group at school and work, the scientists compared the effect of three scenarios.

In one scenario, they assumed no interventions and no holidays were in place.

In another the study assumed no physical distancing measures, but school winter school break and Lunar New Year holidays as normal.

In the third, the researchers modelled intense control measures with school closed and only about 10 per cent of the workforce -- eg, health-care personnel, police, and other essential government staff -- working during the control measures.

They also estimated the impact of lifting control measures in a staggered way, and during different stages of the outbreak in March and April.

Based on these analyses, Prem and her team suggest that the normal school winter break and Lunar New Year holidays may have had little impact on the progression of the outbreak had schools and workplaces opened as usual.

But they said putting these extreme measures in place to reduce contacts at school and workplaces may reduce case numbers and the size of the epidemic peak, while also delaying it.

The researchers noted that the effects of the distancing measures may vary by age, with the greatest reductions in new cases among school children, and the elderly.

The least effects, they said, were among working-aged adults.

However, when these interventions are relaxed, the scientists said case numbers are expected to rise.

On further analysis, the scientists suggested that physical distancing measures may be most effective if the staggered return to work commences at the beginning of April -- potentially reducing the median number of new infections by 24 per cent up to the end of 2020, and delaying a second peak until October.

"Our results won't look exactly the same in another country, because the population structure and the way people mix will be different,"said study co-author Yang Liu from the London School of Hygiene & Tropical Medicine.

"But we think one thing probably applies everywhere: physical distancing measures are very useful, and we need to carefully adjust their lifting to avoid subsequent waves of infection when workers and school children return to their normal routine.

If those waves come too quickly, that could overwhelm health systems," Liu said.

The researchers, however, noted that the study came with some limitations, including that it assumed no difference in susceptibility between children, and that the extreme distancing measures used in Wuhan may have increased the transmission within households.

"The study by Kiesha Prem and colleagues inThe Lancet Public Healthis crucial for policy makers everywhere, as it indicates the effects of extending or relaxing physical distancing control measures on the coronavirus disease 2019 (Covid-19) outbreak in Wuhan, China," said Tim Colbourn from the University College London in UK, who was not involved in the study.