As a newly emerging infectious disease, New Coronary Pneumonia has no special drugs and vaccines worldwide. Therefore, countries mainly use non-pharmaceutical interventions (NPIs) to contain the epidemic. China’s strategy for containment of non-pharmaceutical interventions is effective, but how effective are these measures? What is the timing of its application? To answer these questions, a quantitative assessment is required.
On May 4, local time, the top academic journal Nature published the research of the scientific research team of China, Britain and the United States. The study found through modeling that the three major non-pharmaceutical interventions used in China not only curbed the development of the new crown epidemic in China, but also won a time window for the world. The study pointed out that if a strong non-pharmaceutical intervention “combination boxing” is not implemented, the number of new crown cases in China may increase by 67 times to more than 7 million people.
The above research comes from a number of research teams including Southampton University, Fudan University, Wuhan Center for Disease Control, Harvard University, Johns Hopkins University, etc.
Researchers used epidemiology and anonymous human activity data to establish a model framework that uses daily travel networks to simulate outbreaks and intervention programs across China. The model estimates that as of February 29, 2020, there are a total of 114,325 cases of COVID-19 in mainland China (interquartile range 76767-164576). Without non-pharmaceutical interventions (NPI), COVID-19 cases in mainland China may increase by 67 times (interquartile range 44-94 times). This means that without intervention, there will be nearly 7.66 million new crown infections in mainland China.
Researchers used epidemiology and anonymous human activity data to establish a model framework that uses daily travel networks to simulate outbreaks and intervention programs across China. The model estimates that as of February 29, 2020, there are a total of 114,325 cases of COVID-19 in mainland China (interquartile range 76767-164576). Without non-pharmaceutical interventions (NPI), COVID-19 cases in mainland China may increase by 67 times (interquartile range 44-94 times). This means that without intervention, there will be nearly 7.66 million new crown infections in mainland China.
The study also found that: Compared with travel restrictions and reduced person-to-person contact, early detection and isolation of cases can prevent more infections. However, only when a variety of non-pharmaceutical interventions are applied in concert can the strongest and fastest curbing effect be achieved.
If social alienation measures can be maintained, then the removal of travel restrictions from February 17, 2020 does not seem to cause an increase in cases nationwide. The study found that it helps to increase people ’sUnderstanding of non-pharmaceutical interventions on ID-19 and providing information for response efforts worldwide.
Three categories of non-pharmacological interventions
Three categories of non-pharmacological interventions
As a newly emerging infectious disease, effective medical interventions must be found within a few months The measures are unrealistic. The current limited medical resources are unable to treat all cases. Therefore, non-pharmaceutical interventions are an important part of public health response to outbreaks.
These measures include quarantine the sick, conduct contact tracing, isolate contacts, travel restrictions, school and workplace closures, and cancel mass gatherings. These measures are aimed at reducing the spread, thereby delaying the emergence of epidemic peaks and reducing the scale of epidemic peaks, to buy time for the recovery of the health care system, and to buy time for the development of vaccines and drugs.
In order to curb the spread of COVID-19 in China and reduce the scale of its outbreak, China ’s non-pharmaceutical interventions (NPI) include three major categories.
First of all, inter-city travel restrictions, This curbed the further spread of the virus during the Lunar New Year holidays. The closure of Wuhan and surrounding cities in Hubei Province was implemented on January 23, two days before the Spring Festival (CNY). Since the Spring Festival, other provinces across the country have also imposed travel restrictions.
The second type of non-pharmaceutical interventions are early identification and isolation of cases , including improved screening, identification, diagnosis, isolation, and reporting of contacts for suspected and confirmed cases. Governments across China have stepped up routine inspections and isolation of travelers from Hubei Province, with a view to detecting COVID-19 infection as early as possible. In particular, improvements in detection and diagnosis have reduced the average interval from symptom onset to laboratory diagnosis from 12 days at the beginning of the outbreak to 3 days at the beginning of February.
The third category of non-pharmaceutical interventions is to implement exposure restrictions and social alienation measures and strengthen personal precautions, such as washing hands to reduce the risk of exposure at the community level. As part of social alienation policies, China encourages people to stay at home as much as possible, cancel or postpone large public events and mass gatherings, and close libraries, museums, and workplaces. In addition, school holidays have also been extended, and the end of the Spring Festival holiday in Hubei Province will start from JanuaryThe 30th was postponed to March 10, and the end of the Spring Festival holiday in many other provinces was extended to February 9.
First of all, inter-city travel restrictions, This curbed the further spread of the virus during the Lunar New Year holidays. The closure of Wuhan and surrounding cities in Hubei Province was implemented on January 23, two days before the Spring Festival (CNY). Since the Spring Festival, other provinces across the country have also imposed travel restrictions.
The second type of non-pharmaceutical interventions are early identification and isolation of cases , including improved screening, identification, diagnosis, isolation, and reporting of contacts for suspected and confirmed cases. Governments across China have stepped up routine inspections and isolation of travelers from Hubei Province, with a view to detecting COVID-19 infection as early as possible. In particular, improvements in detection and diagnosis have reduced the average interval from symptom onset to laboratory diagnosis from 12 days at the beginning of the outbreak to 3 days at the beginning of February.
The third category of non-pharmaceutical interventions is to implement exposure restrictions and social alienation measures and strengthen personal precautions, such as washing hands to reduce the risk of exposure at the community level. As part of social alienation policies, China encourages people to stay at home as much as possible, cancel or postpone large public events and mass gatherings, and close libraries, museums, and workplaces. In addition, school holidays have also been extended, and the end of the Spring Festival holiday in Hubei Province will start from JanuaryThe 30th was postponed to March 10, and the end of the Spring Festival holiday in many other provinces was extended to February 9.
Despite the high economic and social costs, China ’s implementation of non-pharmaceutical interventions across the country has led to a rapid decline in the number of new cases. Previous studies have preliminarily explored the effects of the Wuhan blockade, travel restrictions, airport inspections, and case quarantine tracking to curb the spread of the virus. However, there is currently no comprehensive and quantitative analysis and comparison of the effectiveness and timing of different non-pharmaceutical interventions in China.
Based on COVID-19 ’s epidemiological data and historical and near real-time anonymous population activity data, the researchers developed a random susceptibility-exposure-infection based on the travel network -Removal (SEIR) model to simulate the spread of the new crown epidemic in 340 cities in mainland China since December 1, 2019. Through the model, the researchers conducted a before-and-after comparison analysis to quantify the impact of the three major non-pharmaceutical interventions in China. The model also assesses the risk of the spread of COVID-19 since the travel restrictions were lifted on February 17, 2020.
Simulation and reconstruction of the spread of COVID-19
Simulation and reconstruction of the spread of COVID-19
How should the early epidemic parameters of China ’s new crown epidemic be valued before implementing extensive interventions? The researchers used the epidemiological parameters estimated at the outbreak of Wuhan.
Researchers use mobile phone users ’Baidu location service to obtain inter-city and intra-city population mobility data, as well as nationwide time intervals from onset to reported cases, to measure The effects of three major non-pharmacological interventions. Since the implementation of the intervention measures, China ’s population movement and contact methods have undergone major changes, and the timeliness of case reports has also improved.
Researchers estimate that as of February 29, 2020, there were 114325 COVID-19 cases (interquartile range 76776 – 164576) in mainland China, with Hubei Province accounting for 85%.
Before the Spring Festival, the number of new cases in China increased exponentially, but after the implementation of non-pharmaceutical interventions, the peak of epidemic soon arrived, and the time was exactly within the week of the Spring Festival holiday. The model’s prediction of epidemics and peaks is highly consistent with the data reported on the date of onset. The model ’s daily estimates are also highly correlated with reporting data across time and regions.
Researchers estimate that as of February 29, 2020, there were 114325 COVID-19 cases (interquartile range 76776 – 164576) in mainland China, with Hubei Province accounting for 85%.
Before the Spring Festival, the number of new cases in China increased exponentially, but after the implementation of non-pharmaceutical interventions, the peak of epidemic soon arrived, and the time was exactly within the week of the Spring Festival holiday. The model’s prediction of epidemics and peaks is highly consistent with the data reported on the date of onset. The model ’s daily estimates are also highly correlated with reporting data across time and regions.
As of February 29, 2020, there is a significant overall correlation between the number of cases estimated by the model and the number of cases reported by provinces (p <0.001, R2 = 0.86) When predicting the presence or absence of new crown cases in a city, the model's sensitivity (91%, 280/308) and specificity (69%, 22/32) are also very high.
Quantify the impact of different non-pharmaceutical interventions
Quantify the impact of different non-pharmaceutical interventions
Model predictions show that if there are no non-pharmaceutical interventions, as of February 29, China ’s COVID The number of -19 cases will be much higher than the current actual value. Among them, Wuhan City will increase by 51 times (interquartile range 33-71 times), and the number of cases in other cities in Hubei Province will increase by 92 times (interquartile range 58-133 times). The number of urban cases in other provinces will increase by 125 times (the quartile range is 77-180 times).
However, the apparent effects of different interventions vary.
The blockade on Wuhan failed to completely prevent the virus from spreading out of Wuhan, because the blockade was implemented during the relatively late period of the Spring Festival return home. However, if intercity travel restrictions are not enforced, Wuhan Other cities and provinces will usher in more cases of new crowns from Wuhan, and the affected geographic area will be expanded to remote western China.
Generally speaking, early detection and isolation of cases can prevent infections more quickly and substantially (5 times vs. 2.6 times) than reducing the level of contact and social alienation between people nationwide. However, if there is no reduction in human-to-human contact interventions, the epidemic in the entire region will multiply in the long run. Therefore, the comprehensive non-pharmaceutical intervention measures have the strongest and fastest curbing effect on the COVID-19 epidemic. The peak of the epidemic comes about one week after the implementation of the comprehensive non-pharmaceutical intervention measures.
Evaluate the timing of the intervention: How much difference will it take one week, two weeks or three weeks?
The blockade on Wuhan failed to completely prevent the virus from spreading out of Wuhan, because the blockade was implemented during the relatively late period of the Spring Festival return home. However, if intercity travel restrictions are not enforced, Wuhan Other cities and provinces will usher in more cases of new crowns from Wuhan, and the affected geographic area will be expanded to remote western China.
Generally speaking, early detection and isolation of cases can prevent infections more quickly and substantially (5 times vs. 2.6 times) than reducing the level of contact and social alienation between people nationwide. However, if there is no reduction in human-to-human contact interventions, the epidemic in the entire region will multiply in the long run. Therefore, the comprehensive non-pharmaceutical intervention measures have the strongest and fastest curbing effect on the COVID-19 epidemic. The peak of the epidemic comes about one week after the implementation of the comprehensive non-pharmaceutical intervention measures.
Evaluate the timing of the intervention: How much difference will it take one week, two weeks or three weeks?
If you can intervene one week, two weeks or three weeks earlier, the number of Chinese cases can be reduced by 66% (quartile range 50%) -82%), 86% (interquartile range 81% -90%), 95% (interquartile range 93% -97%).
The geographic scope of the affected areas will also be reduced from 308 cities to 192, 130 and 61 cities, respectively.
However, if non-pharmaceutical interventions are performed one, two, or three weeks later than the actual time of implementation, cases may increase by three times (quartile) Number range 2-4), 7 times (interquartile range 5-10) or 18 times (interquartile range 11-26).
Assessment of the lifting of travel restrictions
The geographic scope of the affected areas will also be reduced from 308 cities to 192, 130 and 61 cities, respectively.
However, if non-pharmaceutical interventions are performed one, two, or three weeks later than the actual time of implementation, cases may increase by three times (quartile) Number range 2-4), 7 times (interquartile range 5-10) or 18 times (interquartile range 11-26).
Assessment of the lifting of travel restrictions
After the intervention was implemented, the outbreak outside Hubei Province was contained at a low level in early March (daily New cases <10 cases, excluding imported cases), and Hubei Province may need 4 weeks to reach the same level as other provinces.
However, if the population exposure level returns to the normal level of previous years, the removal of travel restrictions from February 17 may cause the number of cases to rise again. Therefore, the model shows that by the end of April, even maintaining a limited degree of social distance (for example, an average reduction of 25% of contacts) will help ensure that the epicenter of COVID-19 like Wuhan will contain the epidemic.
The model is very sensitive to the number of basic infections (R0). If R0 is higher, the epidemic peak will also be higher and appear later, and it needs more to contain the epidemic. Long time. Sensitivity analysis also shows that under different epidemiological parameters and transmission sensitivity, the model can effectively measure the relative change of the intervention effect.
Researchers ’findings indicate that the coordinated non-pharmaceutical intervention facilities have greatly curbed the spread of the new crown epidemic in China. Earlier implementation may greatly reduce the outbreak and geographical extent of the outbreak. Conversely, delaying the response will lead to a larger outbreak.
China ’s strong, multi-pronged containment avoids worse conditions and slows the spread of the new coronavirus worldwide. China provides a time window and preparation opportunities for curbing the spread of COVID-19 in other parts of the world and reducing its impact.
The researchers ’results suggest three key points. First, population movement and close contact play an important role in the spread of the new crown. Since the blockade of Wuhan was in the late Spring Festival period, travel restrictions could completely prevent the virus from spreading out of Wuhan, but this did prevent more cases from being exported from Wuhan to a wider area.
Second, three non-pharmacological interventionsThe importance and impact of measures are different. Compared with travel restrictions, better detection and isolation of cases and social alienation may have a greater impact on the control of the epidemic. The intervention of social alienation reduces people’s contact with travelers from outbreak centers. This may be particularly useful in curbing the spread of the virus to the wider community and reducing the risk of asymptomatic or mild infections.
Third, considering that work is being resumed in China, China should at least consider retaining some non-pharmaceutical interventions to ensure the control of the outbreak and avoid another outbreak. For example, considering cases imported from other countries and asymptomatic or subclinical infections found in China, the identification and isolation of early cases should continue to be maintained, which may also help prevent or delay the second wave of outbreaks.
