By Kent R. Kroeger (January 31, 2020)
The news on the Wuhan Virus (2019-nCov) outbreak has been mostly negative in the barely two weeks it has been on the daily news agenda.
Here is a sampling just from this morning:
The New York Times reports that the World Health Organization (WHO) is now declaring a global health emergency due to 2019-nCov, after declining to make that declaration a week ago.
CNN reports on a German study published yesterday in the New England Journal of Medicine showing how people can spread the Wuhan coronavirus (2019-nCov) when they are asymptomatic. “There’s no doubt after reading this paper that asymptomatic transmission is occurring,” said Dr. Anthony Fauci, director of the U.S. National Institute for Allergy and Infectious Diseases. “This study lays the question to rest.”
CNN also reports 62 countries have implemented some form of immigration control on Chinese citizens. “Six countries have tightened visa rules for Chinese citizens, four have restricted Chinese citizens’ entry into their countries, and five have launched restrictive measures on anyone from Hubei or with recent travel history to the province,” according to the Chinese Foreign Ministry.
AP reports that the American Airlines pilot union is suing to stop the carrier from flying to China, telling its pilots in a statement “not to operate flights there because of the spreading coronavirus outbreak.”
If you are starting to feel anxious about this fast-spreading virus, you cannot be blamed.
But here is some possible good news. According to WHO’s own data, the rate at which the virus is spreading is already declining, and if this trend continues, the worst may soon be over.
Figure 1 shows the day-to-day percentage increases in the number of confirmed 2019-nCov cases. Since the second day of WHO’s public reporting on 2019-nCov, the day-to-day percentage increases in the cumulative number of cases has been in a near straight-line decline.
Figure 1: Day-to-day % Change in Cumulative Total of 2019-nCov cases
If this second-order trend continues, the total number of 2019-nCov cases may not exceed 20,000 when the health crisis is officially declared over — probably sometime in late spring.
Not so fast…
Let us construct a very preliminary forecast model for the cumulative growth in 2019-nCov confirmed cases.
Previous research on the 2003 Severe Acute Respiratory Syndrome (SARS) showed the cumulative number of cases can be modeled through a logistic function (S-curve), sometimes referred to as the Ratkowsky Sigmoidal Model. The following equation describes this model:
where y is the cumulative number of diagnosed cases, t is time (measured here in days), a is the parameter for the maximum number of cases (estimated during the modeling process), b is the parameter that determines the position of the S-curve along the time axis, and c is the parameter that changes the slope of the disease’s growth relative to time.
Applying this simple modeling equation and using the 2019-nCov data available on the WHO website, I forecast that the 2019-nCov will max-out at 15,706 confirmed cases (±241 cases) and, assuming it maintains its current mortality rate (2.2 percent), will kill 341 people ( ±5 people). Furthermore, 2019-nCov will reach these maximum levels within the next month.
That is a very optimistic forecast, to be sure, and I am fully aware of the limited number of data points and how sensitive my forecast is to small deviations in the daily data. Furthermore, viruses routinely mutate without notice and generate secondary outbreaks, rendering previous prediction models obsolete.
The next WHO situation report could significantly alter the prediction made in this essay.
A casual inspection of the WHO’s most recent confirmed cases and fatalities relative to the 2003 SARS virus should give anyone pause suggesting the 2019-nCov health crisis may soon be over (see Figures 2 and 3 below).
Figure 2: Day-to-day % Change in Cumulative Total of 2019-nCov cases
Figure 3: Day-to-day % Change in Cumulative Total of 2019-nCov cases
The 2019-nCov virus remains significantly ahead of the SARS virus that ultimately infected 8,096 people and killed 774, most of which occurred over an 80-day period.
It is hard for Western news media to resist keeping the general public in a constant sense of low-level panic. Give the media actual data to support their narrative, as the 2019-nCov virus has been doing since mid-January, and the news media is in its programming wheelhouse.
But reality eventually catches up and, at least tentatively, the WHO data on 2019-nCov is indicating China’s heroic effort to stop the virus may have worked much sooner than anyone expected.
Of course, we are talking about a virus that can morph and mutate in the blink of an eye and re-emerge more infectious and deadlier than ever.
Any forecast I’ve made here must be balanced against the unpredictable nature of these biological demons.
Yet, I see significant hope in the recent WHO data that the 2019-nCov is going to fade away much sooner than currently being reported in the media. If my forecast turns out to be accurate, it will because the Chinese government took decisive action quickly and efficiently, on a scale probably never before seen in human history.
Let us hope my forecast is correct.
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