An epidemiologic modelling study to forecast the potential spread of coronavirus disease 2019 (COVID-19) in China predicts that a second surge would be harder to contain. The model was also designed to inform decisions on relaxing restrictions and found that a second wave could require more extensive restrictions than were initially imposed.
"The finding is critical to governments globally, because it warns against premature relaxation of strict interventions," emphasized Sunquing Xu, MD, and Yuanyuan Li, MD, Key Laboratory and Environment and Health, Ministry of Education and Ministry of Environmental Protection, Wuhan, China, in commentary
accompanying the study.
In their mathematical modelling
of COVID-19 spread, Kathy Leung, PhD, of the World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health; Li Ka Shing, faculty of medicine, the University of Hong Kong, Hong Kong Special Administrative Region, China; and colleagues analyzed local health commission data of confirmed COVID-19 cases between mid-January through the end of February from 4 major cities in China (Beijing, Shanghai, Shenzhen and Wenzhou), and 10 provinces that reported high numbers of cases, outside the Hubei province which encompassed the epidemic epicenter in Wuhan.
Leung and colleagues constructed epidemic curves for each location by date of symptom onset and the period of delay between disease onset and the case being reported. These were incorporated into the modelling of weekly reproductive numbers of cases resulting from contact with one infected individual. The investigators also modelled the potential effects of relaxing control measures after the first wave of infections, analyzing different scenarios of restriction which might be imposed to confront rising reproductive numbers.
The reproductive number had decreased substantially in all selected cities and provinces since January 23rd
, when control measures were implemented. The investigators determined that the overall reproductive number had been effectively reduced below 1 (compared to the initial estimated rate in Wuhan of 2.2).
The team also calculated a confirmed case-fatality risk (cCFR) in the 4 major cities and across all 31 provinces of China. The cCFR outside Hubei was 0.98% (95% CI, 0.82–1.16), approximately 5 times lower than in Hubei (5.91%, CI 5.73–6.09).
There were significant differences in cCFR between regions and locales, which the researchers correlated to differences in provincial per capita gross domestic product and availability of hospital beds per 10,000.
The study’s senior author, Gabriel Leung, MD, commented in a news release
that a second wave could sweep over these distinctions. "Even in the most prosperous and well-resourced megacities like Beijing and Shanghai, health care resources are finite, and services will struggle with a sudden increase in demand."
The investigators conclude that if relaxed containment measures allowed the reproductive number to increase above 1, in the present conditions without "herd immunity", there would likely be both health and economic loss, "even if aggressive interventions could push the prevalence back to pre-relaxation level afterwards."
"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," Leung commented. "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 minimize the impact of a possible second wave of infections."
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