There has been much talk and much misinformation being spread about the Corona Virus that is currently hitting China hard. As a statistician, I thought I would help to shed some light on the topic in terms that most of us can understand.
My data that I am using here is taken primarily from two sources:
1. The real time interactive map that John Hopkins University is using to present the current status and trend of the virus.
2. A Lancet Medical Journal article published a week ago and updated/corrected February 4th.
The first image is part of a map of China. The data was updated as of 7:43 p.m. EST on Thursday. It is changing rapidly! The largest red circles that you see represent the provinces that have at least 1000 cases. When I started writing this post earlier this evening, there was only one large red circle, it contained 22,000 of the approximate 31,000 cases. By 8:30 when I saved this map there were two large circles. By 9:00 p.m. there were three. Within the next day or two there will be several more. This by the way is only confirmed cases. There is likely a multiplier effect of those who had such mild symptoms, that they did not even register as cases.
So what do we know?
The virus originated in a market in Wuhan through animal human interaction.
Wuhan is a major transportation hub, and the start of the virus corresponded with the Chinese Lunar New Year, when many were travelling.
The virus is spreading at an exponential rate. The Lancet Journal article estimated a doubling of the number of cases every 6.4 days. From recent data, cumulative deaths are doubling about every four days.
In my graph below I show the cumulative number of deaths. I calculated a best fit line that shows the number of cumulative deaths equal to approximately 1.8 times the square of the number of days since January 20th. To simplify and illustrate: 5 days after January 20th the approximate number of deaths was 5 squared * 1.8 = 45. 10 days after January 20th, it would have been 10 squared * 1.8 = 180. Yesterday, 17 days after the baseline date our calculation is 17 squared * 1.8 = 520, slightly under the actual number of 637. By Sunday night the number of deaths will have climbed to 20 squared * 1.8 = 720. A week from then the number of deaths will in excess of 1300. A month from now, 5600. Two months from now, 16,500. I hope these numbers are inflated, but I don’t believe they are. By contrast, SARS killed around 800 people total.
It is spreading quickly because each person has been infecting approximately 2.6 other people.
Currently the virus is killing 2 to 3% of those known to be infected. This number is still very hard to judge as the number of true infections is unknown. Contrast this to SARS which killed 10% of those infected. 2019-nCoV is much less lethal than SARS, but much more contagious.
What does the future hold?
The authors of the Lancet study suggest that the virus will peak in Wuhan sometime in April or May. What the number of dead will be by then is anyone’s guess. The disease seems to be fairly unstoppable in China right now. Regions outside of Wuhan as experiencing the same exponential growth as Wuhan, but a week or two delayed. As they too become epidemic centers, the disease will continue to spread outwards.
So far, the rest of the World has been fairly fortunate. The virus has not been able to get much of a foothold outside of China. There are some countries as risk however, and places like Vietnam, Thailand, and Japan will bear close watching over the next two weeks. The greatest fear is that it might somehow make its way to a continent like Africa, where it is very hard to control the movement of people.
There is a possibility (the jury is still out on this) that people may be infecting others before they start to show symptoms. If so it will be very difficult to contain. Lancet warns that “Independent self-sustaining outbreaks in major cities globally could become inevitable because of substantial exportation of presymptomatic cases and in the absence of large-scale public health interventions.”
The authors of the Lancet study conclude:
Our findings suggest that independent self-sustaining human-to-human spread is already present in multiple major Chinese cities, many of which are global transport hubs with huge numbers of both inbound and outbound passengers (eg, Beijing, Shanghai, Guangzhou, and Shenzhen)…
On the present trajectory, 2019-nCoV could be about to become a global epidemic in the absence of mitigation. Nevertheless, it might still be possible to secure containment of the spread of infection such that initial imported seeding cases or even early local transmission does not lead to a large epidemic in locations outside Wuhan. To possibly succeed, substantial, even draconian measures that limit population mobility should be seriously and immediately considered in affected areas, as should strategies to drastically reduce within-population contact rates through cancellation of mass gatherings, school closures, and instituting work-from-home arrangements, for example. Precisely what and how much should be done is highly contextually specific and there is no one-size-fits-all set of prescriptive interventions that would be appropriate across all settings.
My final thoughts.
Xenophobia (a prejudice against those from other countries) is on the rise in North America, especially against those who look Chinese. My city has a large prep school made up primarily of Chinese students. Many of them must be living fear of what is going on back home. They need our support and our prayers.
God, we pray for China.
We pray for those outside China, who have a real fear of this virus spreading to their countries. I think especially of places like Vietnam, Singapore, Thailand, Japan, and the continent of Africa.
We pray for the health workers and their families who risk their lives in treating this every day.
We pray for wise decisions from our political leaders.
We pray that effective vaccines might be developed quickly.
We pray for hope, where there seems to be not much.
I leave you with a picture of Dr. Li Wenliang. He was one of the whistle blowers who warned the world of the dangers of this virus. He passed away this morning after contracting the virus himself. He was 34.
I will be resuming regular Friday writing at Internet Monk. More on that to come next week.