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Don't Panic, Be Cautious, and Together We Can Stop the Coronavirus Epidemic!
Supplementary Charts
13 April 2020

Since the publication of our paper in the Asia Pacific Biotech News,1 we have continued to monitor the development of the COVID-19 epidemic on the Mainland of China and updated the relevant charts in our original paper on a weekly basis.2 We have prepared this current update, through midnight (2400) of 12 April. We note that the COVID-19 epidemic was essentially over on the Mainland outside of the Province of Hubei by the middle of March, and on the entire Mainland, including Hubei and Wuhan, at the end of March, in accordance with the prediction in our paper. The lockdown in Wuhan has been ended. The Mainland has now largely returned to normal. Concern has now shifted to how to isolate and contain new cases imported into the Mainland from abroad, and similar cases in Hong Kong and Taiwan, which have until very recently been rising fast

In the updated charts, we have adjusted the official data on newly confirmed cases and deaths of Wuhan, Hubei and the Mainland, so as to smooth out their reported surges on a couple of occasions,3 including the one on 12 February, which was primarily caused by a change in the definition of a “confirmed” case in Hubei, including Wuhan, and also to remove some inconsistencies, such as a cumulative total number that declines with time.

Chart 2 confirms that in Mainland ex Hubei, the incidence of the COVID-19 epidemic has actually been relatively mild and generally declining over time. For Mainland cities outside Hubei, such as Changsha, Chongqing, Hangzhou, Nanjing and Shenzhen, the daily numbers of newly identified cases already began to show a declining trend since the beginning of February, even though they also continued to fluctuate up and down. They became essentially zero by the end of February. For Hong Kong, Macau and Taiwan, the daily numbers of newly confirmed cases have all fell to zero on 15 February 2020. However, the epidemic flared up again, especially in Hong Kong and Taiwan, in early March but appeared to be under control more recently because of all the precautionary measures taken at these three areas. The overall picture suggests that the spread of the coronavirus to areas other than Hubei have been largely contained.

In the updated Chart 2A, which begins on 1 March 2020, the daily number of newly confirmed domestic cases outside Hubei is represented by a single line, Mainland ex imports and Hubei. This line is hardly visible and averages 1.5 cases per day since 16 March 2020.4 Similarly, the number of daily newly confirmed cases within Hubei (including Wuhan) has also been essentially zero since 16 March, with an average of 0.1 case per day. In fact, the epidemic has been basically over on the Mainland, where economic activities have already largely returned to normal, initially outside of Hubei, and then in Hubei (including Wuhan) itself. Moreover, the daily newly confirmed cases in Hong Kong and Taiwan, which had risen rapidly since 16 March because of the influx of a large number of returning residents from Europe and North America, also began to decline (respectively 4 and 3 cases on 12 April). However, Hong Kong now has more current COVID-19 cases than any other municipality, province and region on the Mainland, including even Hubei. In the meantime, on the Mainland, newly confirmed cases imported from abroad have also been identified in many places, notably in Beijing, Shanghai, and the Provinces of Guangdong and Heilongjiang. Strict quarantine measures must be taken on the Mainland to prevent the imported cases from spreading and possibly triggering a resurgence of the COVID-19 epidemic.

The updated Chart 3 shows the trajectory of daily numbers of newly confirmed domestic cases on the Mainland from 16 January 2020, after the reallocation of the surges on 27 January and 12 February 2020. The difference between Hubei (including Wuhan) and Mainland ex Hubei was most striking.

The updated Chart 3A, which is Chart 3 but begins on 1 March 2020, shows that almost all of the daily newly confirmed cases on the Mainland since 16 March 2020 have been imported cases. The average number of newly confirmed domestic cases per day during the four weeks from 16 March to 12 April 2020 on the entire Mainland is 1.6. The first imported COVID-19 case was identified on 26 February 2020. The daily number of imported newly confirmed cases averaged 45 for the four weeks 16 March-12 April 2020 (but reached 98 on 12 April 2020). China would be taking steps to prevent the number of imported cases from growing and quarantining any such cases because they may rekindle domestic transmission of the COVID-19 virus in an uncontrollable way.

Instead of the original Chart 4, we introduce a new Chart 4A, which shows the new deaths on the Mainland, excluding imported cases, Mainland ex imported and Hubei, Hubei and Wuhan between 16 January 2020 and 12 April 2020. Chart 4A reflects the reallocation of the surge in the reported number of deaths in Wuhan and Hubei ex Wuhan on 12 February 2020. It is clear from Chart 4A that most of the deaths due to the COVID-19 virus occurred in Hubei and within Hubei in Wuhan. Deaths on the Mainland outside of Wuhan amounted to only 120 since 16 January 2020 (or less than 1.4 per day) compared to 3,341 for the Mainland as a whole.

The updated Chart 5 also reflects the reallocation of the surge in the reported number of deaths in Wuhan and Hubei ex Wuhan on 12 February 2020. Because the cumulative newly confirmed domestic cases to date is no longer rising in Wuhan, Hubei and the Mainland, the instantaneous cumulative mortality rate (the cumulative total number of domestic deaths due to the COVID-19 virus divided by the cumulative newly confirmed domestic cases to date) will continue to rise, as expected, in Wuhan (5.2 percent as of 12 April 2020), Hubei and the Mainland, as there were still 121 seriously ill confirmed COVID-19 patients as of 12 April 2020. Outside of Hubei, the mortality rate of the Mainland has remained steady and been rising very gradually also because the cumulative number of confirmed cases is also no longer increasing. It stood at 0.9 percent as of 12 April 2020, less than one-fifth of the mortality rate of Wuhan. These numbers confirm our assessment that the mortality rate of the COVID-19 virus is relatively low, probably not more than 1 percent, in places where adequate medical care is available.

In the updated Chart 8, the daily newly confirmed cases are compared with the daily newly increased suspected cases for the period beginning on 1 March 2020. Suspected cases are cases that have yet to become confirmed cases pending further clinical observations and/or nucleic acid tests. Once a case is determined one way or the other, it will no long be retained as a suspected case. Thus, in general, the number of new suspected cases should exceed the number of newly confirmed cases, or at least should do so after a short time lag to allow for testing.

The updated Chart 8 shows clearly that the numbers of new suspected cases on the Mainland (excluding imports) and in Hubei and Wuhan have generally continued their declining trends. For the Mainland as a whole, the daily number of new suspected cases averaged 15.3 per day during the week of 6-12 April 2020, compared to an average of 3.6 per day for newly confirmed cases. What is most remarkable is that in Hubei (and Wuhan), there have been zero new suspected cases since 16 March 2020. This reflects the greatly improved availability of medical care in Wuhan and Hubei so that the backlog of unreported and suspected cases has been completely cleared. It further reinforces our confidence that the number of newly confirmed domestic cases in Wuhan, and hence in Hubei province and on the Mainland, is likely to remain essentially zero in the near future. Imported cases are another matter altogether. They must be strictly controlled, isolated and quarantined to prevent a resurgence of the COVID-19 epidemic on the Mainland.


  1. Lawrence J. Lau and Yanyan Xiong, “Don’t Panic, Be Cautious, and Together We Can Stop the Coronavirus Epidemic,” Asia Pacific Biotech News, Special Issue 1, March 2020, pp. 90-107, doi: s0219030320001202.
  2. The weekly updated charts may be found on the webpage of Lawrence J. Lau, http://www.igef.cuhk.edu.hk/people/professor-lawrence-j-lau/.
  3. We have redistributed the “excess” cases and deaths on 12 February proportionally to the days between 16 January and 12 February. The redistribution has no effect on our conclusions. However, it does facilitate comparisons across countries, regions and municipalities.
  4. However, the number of newly confirmed cases was 10 on 12 April, not a large number for the entire Mainland ex Hubei, but should still be carefully monitored.

About the Authors
Lawrence J. Lau is Ralph and Claire Landau Professor of Economics, The Chinese University of Hong Kong, and Kwoh-Ting Li Professor in Economic Development, Emeritus, Stanford University.

Yanyan Xiong is ZJU100 Young Professor, School of Economics, and Research Fellow, Center of Social Welfare and Governance, Zhejiang University.

The authors are most grateful to Professor Dean T. Jamison, Mrs. Ayesha Macpherson Lau, Dr. Kin Bing Wu and Prof. Chen-Ning Yang for their helpful comments and suggestions on earlier drafts of this paper. Responsibility for any errors remains with the authors.


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