The UK is about to enter the Easter bank holiday weekend in a way it hasn’t since wartime. Usually thronged parks, pubs and bars will be eerily empty, a symbol of how COVID-19 has brought life in the UK to a grinding halt. That is the hope, at least.
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In a press briefing earlier today, Dominic Raab, the foreign secretary, urged the general public to stay indoors this weekend.
Some may accuse the government of overreach, especially as there are early hints that the curve is flattening.
A new study conducted by researchers at the University of Hong Kong, rebuts this complacency.
The researchers of the study, published in the Lancet, suggest easing the measures before a vaccine is found risks unleashing a second wave of COVID-19 infections.
The study used a model based on COVID-19 reproduction data from 10 Chinese provinces with the highest number of confirmed cases, as well as the confirmed case-fatality risk in all 31 provinces to determine the potential effects of relaxing lockdown measures after the first wave of infection.
Current data suggests that in regions outside Hubei, the instantaneous reproductive number of COVID-19 – the average number of cases generated by a single infected individual during the outbreak – fell substantially after lock down measures were introduced on January 23, 2020, and has remained below one since then.
When the reproductive number falls below one, the epidemic is likely to die.
This suggests that the epidemic has shifted from one that is expanding rapidly to one that is slowly shrinking.
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However, mathematical modelling to simulate the impact of relaxing current control measures, suggests that premature lifting of these interventions will likely lead to transmissibility exceeding one again, triggering a second wave of infection.
The findings issue a stark warning to countries that are in the early phases of lockdown because they warn against premature relaxation of strict control measures, researchers say.
However, the study did not specifically examine the effect of each intervention, or which one was most effective in containing the spread of the virus.
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“While these control measures appear to have reduced the number of infections to very low levels, without herd immunity against COVID-19, cases could easily resurge as businesses, factory operations, and schools gradually resume and increase social mixing, particularly given the increasing risk of imported cases from overseas as COVID-19 continues to spread globally,” says Professor Joseph T Wu from the University of Hong Kong who co-led the research.
He continued: “Although control policies such as physical distancing and behavioural change are likely to be maintained for some time, proactively striking a balance between resuming economic activities and keeping the reproductive number below one is likely to be the best strategy until effective vaccines become widely available.”
How did the researchers arrive at their conclusion?
In the study, researchers analysed local Health Commission data of confirmed COVID-19 cases between mid-January and February 29, 2020, to estimate the transmissibility and severity of COVID-19 in four major cities – Beijing, Shanghai, Shenzhen, Wenzhou – and ten provinces outside Hubei with the highest number of confirmed COVID-19 cases.
The number of new daily imported and local cases were used to construct epidemic curves for each location by date of symptom onset, and reporting delays – time lags between the onset of a disease and the reporting of cases – were incorporated in the modelling to calculate weekly reproduction numbers.
The researchers also modelled the potential impact of relaxing control measures after the first wave of infection for different scenarios with rising reproduction numbers.
The analyses suggest that in regions outside Hubei, control measures should be lifted gradually so that the resulting reproductive number does not exceed one, or the number of cases will progressively rise over the relaxation period.
Moreover, the estimates suggest that once elevated, simply tightening control interventions again would not reduce the burden back to its original level, and would require extra effort to drive the reproductive number below one in order to revert to the pre-relaxation level – likely resulting in both higher health and economic loss.
“We are acutely aware that as economic activity increases across China in the coming weeks, local or imported infection could lead to a resurgence of transmission,” said co-lead author Dr Kathy Leung from the University of Hong Kong.
She added: “Real-time monitoring of the effect of increased mobility and social mixing on COVID-19 transmissibility could allow policymakers to fine tune control measures to interrupt transmission and minimise the impact of a possible second wave of infections.”
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