Social distancing, keeping people at home, and lockdowns are being implemented in many nations to prevent the spread of the highly infectious severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Some countries that have seen declines in the number of new infections due to lockdowns are now looking to allow people to return to more normal daily routines.
However, researchers warn that there is a risk of a second wave of cases, and lockdowns need to be maintained until there is an effective vaccine against COVID-19 or new case numbers fall to near zero. The latest study is based on the Chinese experience. The study titled, “First-wave COVID-19 transmissibility and severity in China outside Hubei after control measures, and second-wave scenario planning: a modeling impact assessment,” was published in the latest issue of the journal Lancet. The study was funded by the Health and Medical Research Fund, Hong Kong, China.
What was this study about?
The team writes that up until the 18th of March 2020, there were 13,415 confirmed cases of COVID-19 in mainland China outside Hubei province, where the disease began. They explain that the lockdowns and social distancing measures to prevent the public from gathering had a significant impact on flattening the infection spread curve. In this study, they write that they provide an “impact assessment of the transmissibility and severity of COVID-19 during the first wave in mainland Chinese locations outside Hubei”.
Prof Joseph T Wu from the University of Hong Kong, who co-led the research, explained, “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 increased risk of imported cases from overseas as COVID-19 continues to spread globally.”
What was done?
For the study, the team determined an “instantaneous reproduction number (Rt) of COVID-19”. This was determined for Beijing, Shanghai, Shenzhen, Wenzhou, and ten other Chinese provinces. These provinces each had a very high number of COVID-19 positive cases they wrote. Beijing, Shanghai, Shenzhen, and Wenzhou and all the 31 other provinces in China also had a high confirmed Case Fatality Risk (cCFR), they explained. Using a model called the “susceptible–infectious–recovered model,” they determined the impact of relaxing the lockdown or containment efforts of the government after the first wave of the infection is over. They determined its effects on stopping a possible second wave of the infection.
The data for the study was gathered from local health commission data on COVID-19 cases from different Chinese regions between mid-January and the 29th of February.
What was found?
The team calculated and found that the instantaneous reproduction number (Rt) of COVID-19 was substantially reduced since the 23rd of January after the lockdown was in place, and control in social mingling was implemented. Since then, the numbers have remained below 1. The numbers were initially between two and three they wrote. The confirmed case fatality risk or cCFR outside the Hubei province was 0.98 percent. This was five times lower than what was found in Hubei (5.91 percent cCFR in Hubei).
The team deduced that if the preventive measures of lockdown were withdrawn, the Rt would rise above by one, and despite the small size of the epidemic, it could lead to an exponential rise in the case count. This was directly related to the duration of the relaxation they wrote. The harm was substantial even if the government would again use aggressive control measures to bring back the numbers below the baseline.
Implications and conclusions
The researchers explained that aggressive non-pharmaceutical interventions such as lockdown and social distancing were the main contributor to control of the first wave of COVID-19 epidemic outside Hubei. They warn, however, “given the substantial risk of viral reintroduction, particularly from overseas importation, close monitoring of Rt and cCFR is needed to inform strategies against a potential second wave to achieve an optimal balance between health and economic protection.”
Wu said, “Although control policies such as physical distancing and behavioral 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.”
One of the senior authors Prof Gabriel M Leung from the University of Hong Kong, said, “Even in the most prosperous and well-resourced megacities like Beijing and Shanghai, healthcare resources are finite, and services will struggle with a sudden increase in demand. Our findings highlight the importance of ensuring that local healthcare systems have adequate staffing and resources to minimize COVID-related deaths.”
First-wave COVID-19 transmissibility and severity in China outside Hubei after control measures, and second-wave scenario planning: a modelling impact assessment Leung, Kathy et al. The Lancet, https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30746-7/fulltext