Modeling study estimates impact of relaxing control measures on possible second wave of COVID-19 in China

April 8, 2020

Science Daily/The Lancet

Use of real-time monitoring of COVID-19 transmissibility and severity to fine-tune control strategies offers the best chance to minimize second wave of infection in mainland China, outside Hubei province, researchers say in a new study.

New modelling research, published in The Lancetjournal, suggests that China's aggressive control measures appear to have halted the first wave of COVID-19 in areas outside Hubei province, the epicentre of the epidemic. However, given the substantial risk of the virus being reintroduced from abroad, and with economic activity increasing, real-time monitoring of COVID-19 transmissibility and severity is needed to protect against a possible second wave of infection, researchers say.

The study estimates 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 1 since then -- suggesting that the epidemic has shifted from one that is expanding rapidly to one that is slowly shrinking. (The higher the reproductive number, the more transmissible the virus is and the higher the risk for rapid spread. When the reproductive number falls below one, the epidemic is likely to die out.)

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 1 again, resulting in a second wave of infection.

The findings are critical to countries globally that are in the early phases of lock down 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.

"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 continues, "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.

Further analysis suggests that the confirmed case fatality risk (the probability of dying among confirmed cases of COVID-19 as officially reported) outside Hubei was 0.98% -- which is almost six times lower than in Hubei (5.91%) -- and varied substantially among different provinces, based on economic development and availability of health-care resources. Among the ten provinces with the largest number of confirmed cases, case fatality ranged from 0% in prosperous regions like Jiangsu to 1.76% in less developed provinces such as Henan.

"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," says senior author Professor Gabriel M Leung from the University of Hong Kong. "Our findings highlight the importance of ensuring that local health-care systems have adequate staffing and resources to minimise COVID-related deaths."

In December 2019, a novel coronavirus (SARS-CoV-2) emerged in Wuhan city and spread across China. Stringent restrictions on the movement of people and goods were introduced nationwide on January 23. These measures have impacted on people's livelihood and personal liberties, as well as lost economic opportunity. Since February 17, restrictions have been progressively relaxed in several provinces, and factories and offices are gradually reopening.

In the study, researchers analysed local Health Commission data of confirmed COVID-19 cases between mid-January and 29 February, 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 1, 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 1 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," says co-lead author Dr Kathy Leung from the University of Hong Kong. "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."

Despite these important findings, the study has some limitations, including that the estimated reproductive numbers were based on the reported number of confirmed cases, and the time and dates of symptom onset were unavailable for some provinces and relied on data derived from Shenzhen. Finally, a limited number of simulations for relaxing control measures were done, and did not specify which interventions or public responses to the epidemic might correspond to each of these scenarios.

Writing in a linked Comment, lead author Dr Shunqing Xu (who was not involved in the study) from Huazhong University of Science and Technology in China says: "Case fatality rate (CFR) is one of the important unknowns of COVID-19...Leung and colleagues found the confirmed CFR was correlated with provincial per capita gross domestic product and the availability of hospital beds per 10,000. In Wuhan, the CFR was up to 5.08% by March 28, 2020. The remarkable difference in the CFR between these locations and Wuhan might be attributed to the difference in the degrees of health-care capacity. Therefore, consideration should be given to the variations in health-care capacity when implementing interventions."

https://www.sciencedaily.com/releases/2020/04/200408184717.htm

First study on the health conditions of adults one month into COVID-19 lockdown

Early evidence of people's health conditions after one-month of lockdown in China

April 8, 2020

Science Daily/University of Sydney

A new study provides some of the earliest pieces of evidence that the COVID-19 outbreak affected people mentally as well as physically.

The preliminary results reveal adults in locations more affected by COVID-19 had distress, and lower physical and mental health, and life satisfaction.

Researchers from the University of Adelaide, Tongji University and University of Sydney surveyed 369 adults living in 64 cities in China after they had lived under one-month of confinement measures in February this year.

Led by Dr Stephen Zhang from the University of Adelaide, the study identifies adults with existing health conditions and those who stopped working as most at risk of worse mental and physical health.

"As many parts of the world are only just beginning to go into lockdown, we examined the impact of the one-month long lockdown on people's health, distress and life satisfaction," said Dr Zhang.

"The study offers somewhat of a 'crystal ball' into the mental health of Australian residents once they have been in the lockdown for one month."

More than a quarter of the participants worked at the office during the lockdown period while 38 percent worked from home and 25 percent stopped work due to the outbreak.

Published in Psychiatry Research, the study suggests adults living in locations more affected by COVID-19 reported negative life satisfaction only among adults with chronic medical issues but not for those without existing health issues.

Co-author on the study, Professor Andreas Rauch from the University of Sydney said; "We weren't surprised that adults who stopped working reported worse mental and physical health conditions as well as distress. Work can provide people with a sense of purpose and routine, which is particularly important during this global pandemic."

Study participants who exercised for more than 2.5 hours per day reported worse life satisfaction in more affected locations while those who exercised for half an hour or less during the lockdown reported positive life satisfaction.

"We were really surprised by the findings around exercising hours because it appears to be counter-intuitive," said lead author Dr Zhang.

"It's possible adults who exercised less could better justify or rationalise their inactive lifestyles in more severely affected cities. More research is needed but these early findings suggest we need to pay attention to more physically active individuals, who might be more frustrated by the restrictions."

https://www.sciencedaily.com/releases/2020/04/200408102137.htm

Rapid infectious disease shifts in Chinese children and adolescents prior to COVID-19

Science Daily/Murdoch Children’s Research Institute

Deaths of children and adolescents in China due to infectious diseases were becoming rare prior to the covid-19 pandemic, according to a new study.

Quarantinable conditions with high death rates such as cholera and plague had effectively disappeared and many traditional and vaccine-preventable infectious diseases of childhood including diarrhea, measles and rubella became uncommon.

The research, led by the Murdoch Children's Research Institute (MCRI) and Peking University and published in the British Medical Journal, found the leading causes of death from infectious diseases in China had shifted markedly over a 10 year period from rabies and tuberculosis to HIV/AIDS.

But overall deaths from infectious diseases decreased steadily between 2008-2018 from 0.21 per 100,000 population in 2008 to 0.07 per 100,000 in 2017.

MCRI Professor George Patton said until now no study had reported on recent trends in infectious diseases among children and adolescents in China.

The new research analysed national surveillance data across 31 mainland Chinese provinces. It involved 5 million students aged six to 22 years, and involved 44 notifiable infectious diseases.

Study author Yanhui Dong, from Peking University, said China had made 'remarkable progress' in infectious disease control in this age group.

But Dr Dong said while animal-to-human infections like bird flu remained low, the potential for major outbreaks like SARS-CoV-2 remained a very real possibility.

After the SARS outbreak in 2003, China made substantial investments in laboratory testing, surveillance system enhancement, national intervention programs for specific diseases, and collaboration with international partners.

Professor Patton said despite the progress, China faced new challenges in responding to seasonal and unpredictable new infectious diseases in children and adolescents.

Comprehensive national surveillance systems and rapid proactive government responses would be an integral part of future infectious disease control in China and around the world, he said.

"China will need to continue its successful efforts against older infectious diseases of children and adolescents, including measles, tuberculosis, rabies, and scarlet fever and now scale-up vaccination for mumps, seasonal influenza, and hepatitis B," Professor Patton said.

"Along with the rest of the world, China will also need greater vigilance around the highly transmissible seasonal and unpredictable diseases that we have seen in the past two decades including SARS, MERS, novel influenzas, Zika, Ebola and now the new SARS-CoV-2 virus."

Despite expanding the national childhood immunisation program in 2008, the most common infections in early childhood in China were still vaccine preventable diseases and gastrointestinal and enterovirus diseases, such as hand, foot and mouth disease.

Sexually transmitted diseases and bloodborne infections largely affected older adolescents.

Dr Dong said the significant increase of HIV/AIDs and STI's among 15-24 year olds seemed related to high risk sexual behaviours and poor awareness of infection risks.

"There is a pressing need for more school and university-based sex education programs as well as peer education, and access to rapid testing for sexually transmitted infections," Dr Dong said.

Dr Dong said the data especially highlighted the need for prevention programs to pivot towards a different set of risks, which would also require different interventions.

Researchers from the Chinese Centre for Disease Control and Prevention, the University of Melbourne and The Royal Children's Hospital also contributed to the study.

Key findings for the six to 22 year age group in China included:

• Deaths from infectious diseases has decreased between 2008-2018 from 0.21 per 100,000 population in 2008 to 0.07 per 100,000 in 2017

• Quarantinable conditions with high death rates have effectively disappeared

• Zoonotic infections like bird flu remained low but there is potential for major outbreaks

• Notifiable infectious diseases decreased from 280 per 100,000 in 2008 to 162 per 100,000 in 2015, but rose again to 242 per 100,000 in 2017, largely related to mumps and seasonal influenza

• Most vaccine preventable diseases were at low levels, but seasonal variation in mumps, rubella, measles, and influenza suggested these diseases should remain a priority for public policy

• Vectorborne diseases, such as those transmitted by mosquitoes and fleas, have declined

• Gastrointestinal and enterovirus diseases remained constant, but typhoid, paratyphoid, and dysentery continued to decline

• Tuberculosis remained the most common bacterial infection, although cases of scarlet fever doubled between 2008 and 2017

• Sexually transmitted diseases and bloodborne infections increased significantly. By the end of 2018, 149,000 people with newly diagnosed HIV/AIDS had been reported, 95 per cent of which were sexually transmitted. Of these, 16,000 new HIV/AIDS cases were reported among 15-24 year olds

• Children and adolescents in western China continued to carry a disproportionate burden from infectious diseases

https://www.sciencedaily.com/releases/2020/04/200403103957.htm

China's control measures may have prevented 700,000 COVID-19 cases

March 31, 2020

Science Daily/Penn State

China's control measures during the first 50 days of the COVID-19 epidemic may have delayed the spread of the virus to cities outside of Wuhan by several days and, by interrupting transmission nationwide, prevented more than 700,000 infections across the country, according to an international team of researchers. The findings, published March 31 in the journal Science, could be useful to countries that are still in early phases of the COVID-19 outbreak.

"The number of confirmed cases in China by day 50 (February 19) of the epidemic, was around 30,000," said Christopher Dye, visiting professor of zoology and visiting fellow at the Oxford Martin School, University of Oxford. "Our analysis suggests that without the Wuhan travel ban and the national emergency response there would have been more than 700,000 confirmed COVID-19 cases outside of Wuhan by that date. China's control measures appear to have worked by successfully breaking the chain of transmission -- preventing contact between infectious and susceptible people."

The researchers used a unique combination of case reports, human movement data and public health intervention information to investigate the spread and control of COVID-19. They examined the movements of 4.3 million people out of Wuhan before the travel ban, the types and timing of control measures implemented across the cities of China and the numbers of COVID-19 cases reported each day in every city.

"One fascinating aspect of our work is that it shows the power of novel data streams such as cell phone mobility data," said Ottar Bjornstad, distinguished professor of entomology and biology, Penn State. "Since the time period we studied included the Spring Festival holiday and Chinese Lunar New Year, we were able to compare patterns of travel into and out of Wuhan during the outbreak with cell phone data from two previous spring festivals. The analysis revealed an extraordinary reduction in movement following the travel ban of January 23, 2020. Based on this data, we could also calculate the likely reduction in Wuhan-associated cases in other cities across China."

The team's model also analyzed the specific effects of the Wuhan shutdown and found that it delayed the arrival of COVID-19 in other cities by several days. "This delay provided extra time to prepare for the arrival of COVID-19 in more than 130 cities," said Huaiyu Tian, associate professor of epidemiology, Beijing Normal University.

These cities banned public gatherings, closed entertainment venues and suspended public transport, among other actions. As a result, they reported 33% fewer confirmed cases during the first week of their outbreaks than cities that did not implement a Level 1 Response.

While the control measures taken thus far have reduced the number of COVID-19 infections to very low levels, China, is by no means out of the woods.

"Given the small fraction of the Chinese population that has been infected, a much larger number of people remains at risk of COVID-19," said Tian. "We are acutely aware that resident or imported infections could lead to a resurgence of transmission."

Bjornstad noted that SARS-CoV-2 may establish as a human endemic globally in the years to come.

"It is critical to keep in mind that this virgin epidemic likely will affect people of different ages and susceptibilities, and therefore have different fatality levels, than possible subsequent seasonal epidemics," he said.

https://www.sciencedaily.com/releases/2020/03/200331130012.htm