Why the Number of Confirmed Cases of the 2019-nCoV Coronavirus is still growing exponentially?
The number of confirmed cases and deaths of the new Wuhan Coronavirus (2019-nCoV) has been increasing exponentially in the past few weeks, as shown in Figure 1. It is so scary that many countries have already banned Chinese from coming in, or required them to be quarantined for 14-day. Air traffic has been suspended or restricted to and from Mainland China. Besides putting the epicenter of the virus: Wuhan (a 12m population city) under lockdown, many mega-cities in Mainland China are also put under a partial lockdown or restricted travel measures, including Hangzhou, Wenzhou, Guangzhou and Sichuan. (Reuters, 2020)
However, even with such extreme measures for weeks, the number of confirmed cases of the Coronavirus does not seem to be under control. In contrast, the numbers of confirmed cases and deaths are still going up exponentially. Many other cities outside Mainland China are now having the Phase 2 Outbreak, with a similar pattern of an exponentially increasing trend in the number of confirmed cases. For example, Figure 2 compares the numbers of confirmed cases in the world (blue curve, left-axis) and in Hong Kong (red curve, right-axis). The left-axis is 1000 times the right-axis, indicating that their rates of increase are almost the same.
More importantly, there are three major reasons why the Wuhan Coronavirus spreads so fast and so wide:
- the delay in disclosing information about the virus from the Wuhan Government (Ratcliffe, 2020);
- a huge number of people in China started to travel during the Chinese New Year holiday; and
- the infected can spread the virus even without any detectable symptoms.
It must be highlighted that the first date of the confirmed cases was NOT Dec 31, 2019. This is the official date of announcing the discovery of a new type of Coronavirus in Wuhan by the Wuhan government, and there have already been 41 confirmed cases on this first day. The reason is simply that they had not got the approval of disclosing the information. Based on an international experts’ paper published in Lancet, the earliest date of the first confirmed case is Dec 1, 2019. It traces back 30 days earlier than the official date. It also explains why the spread in Wuhan could be so vigorous.
Figure 3 shows the number of cases (all the 41 cases were confirmed to be 2019-nCoV afterward) and only 27 cases had exposed to the Huanan Seafood Wholesale Market. It triggers a query that the source of the virus may not be the seafood market, as the first case had not been exposed to the site. It also implies that the virus has been spreading for a month before the first official release of the virus information.
It was reported that the citizens in Wuhan basically had not taken any protective measures before Jan 20. The Mayor of Wuhan told the press to the effect that they knew the dire situation well before the date but “local government was obliged to seek permission before fully disclosing information about the virus, and that their response had since become ‘tougher than others’”. (Ratcliffe, 2020) It implies that the delay in disclosing the information is due to the approval process.
Another team of international experts (Read et al., 2020) estimated that the detected number of cases was just about 5.1% of the epidemic size (ascertainment rate). Based on their estimation, there would be about 13000 confirmed cases in Mainland China or about 260,000 cases of infected on Feb 4, 2020. It is found to be an under-estimation, as the number of confirmed cases on Feb 4 was 20,438 in Mainland China, which is almost 57% more than the estimation (Figure 4).
The Chinese New Year holiday is the most important holiday in Mainland China, there is a tradition that the whole family would gather together for a celebration, and many families would also take this long holiday opportunity to travel inbound or outbound. The huge number of travelers is common once every year and is coined as the Spring Festival Travel Rush. It is reported that, in 2019, three billion trips were made during the 40-day Spring Festival travel rush (Chen, 2019). With the busiest high-speed rail networks in the world and a large number of domestic and international flights to and from China, the spread of the virus can reach the whole country within a month, and many other countries within a quarter.
In fact, the bubonic plague in 1894 and the SARS in 2003 were both happened at almost the same period of time that was around the Chinese New Year. (Yiu, 2007) In other words, now when the Chinese New Year holiday is over, billions of travelers are traveling back to their hometowns to work or study, the second phase of large-scale spread in China can be envisaged once the government relaxes the travel restrictions. Else, if the government extends the holiday and tightens the travel restrictions further, then the economy of China would be seriously suffered, especially when the investors switch their purchases or manufacturing bases to other countries. It is a dilemma!
Chen, L. (2019) Three billion trips made during 40-day Spring Festival travel rush, China Daily Mar 1. http://global.chinadaily.com.cn/a/201903/01/WS5c78a6aba3106c65c34ec2af.html
Huang, C. et al. (2020) Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China, Lancet January 24, DOI:https://doi.org/10.1016/S0140-6736(20)30183-5
Ratcliffe, (2020) China coronavirus: mayor of Wuhan admits mistakes, The Guardian Jan 27. https://www.theguardian.com/science/2020/jan/27/china-coronavirus-who-to-hold-special-meeting-in-beijing-as-death-toll-jumps
Read, J.M., Bridgen, J.R.E., Cummings, D.A.T, Ho, A. and Jewell, C.P. (2020) Novel Coronavirus 2019-nCoV: early estimation of epidemiological parameters and epidemic predictions, 23 Jan. medRxiv — the preprint server for health sciences. https://doi.org/10.1101/2020.01.23.20018549
Reuters (2020) Chinese city lockdown approaches Shanghai, The Jakarta Post Feb 4. https://www.thejakartapost.com/news/2020/02/04/chinese-city-lockdown-approaches-shanghai.html
Yiu, C.Y. 姚松炎 (2007) 香港鼠疫、衛生環境與建築，歷史照片研究比賽公開組冠軍，香港歷史博物館。