Very simplistic but so far surprisingly accurate (until the day I put it up) model predicting the number of people affected by corona virus on a given date. (Also called novel coronal virus, nCov-19, Covid19 or COVID-19)
If the official numbers are accurate and the rate at which new cases is slowing, then I am very grateful for that. Within China the official rate of new cases and deaths, over the past three days, is close to linear (~2100 cases a day and ~130 deaths). However, there are reasons to suspect that official numbers are underestimating the total number of cases. Outside of China the number of new cases continues to appear to be exponentially increasing at around 13% a day in some places. Within China there are unofficial reports of people being quarantined in hotels without being diagnosed or having access to doctors. There was also a report of China not counting people as having the virus if they are not showing enough symptoms, even if tests come back positive. I hope these rumors are false but is difficult to know given Chinese control of the media, and the negative financial impact of admitting the situation is worse.
China may see over 400,000 infected and over 9000 dead by the end of February if their containment measures are not effective. Without effective containment measure the world may see 24 million cases and over 600,000 dead by the end of March. Over 1.3 billion infected and over 30 million dead by the end of April. These are worst case numbers based on official data. Everyone having been infected and 10-20% of the world dead by the end of May.
The numbers presented here are shocking. The rate of infection appears to be roughly compounding at 14% daily. 10-20% of those infected die. The numbers indicate, from the time a person is officially counted as infected to the time they have an outcome (recovery or death) is about 12-16 days. This report indicates how quickly the virus will spread around the world if it continues to spread at the same rate. It is unlikely that it will spread at the same rate outside of China if governments and the World Health Organization take decisive action. Even within China it is unlikely that it will continue to spread at the same rate given that quarantine measures are in place and the public is now informed enough to take precautions to protect themselves. With that said, as of 2/14/2020 there are only 3 cases reported in India, 1 on the continent of Africa, 8 in the Middle East. It seems likely that these areas are failing to take precautions and test people so the number of cases in these places could be higher than reported.
The numbers presented here are official numbers. Sources of information: https://www.worldometers.info/coronavirus/ https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6
Many factors affect the spread of the virus. Some places receive very few international travelers and thus the virus will take longer to reach them than indicated. Countries which take action to track down or follow those who are more likely to have been infected and who put quarantine measures and travel restrictions in place early will be much less likely to lose between a 5th and a 10th of their populations which appears to be what China is facing.
It is suspected that China has been downplaying the total number of people infected and people who have died. Reason China might do this include lack of testing supplies or testing facilities. People may have the disease who are too sick to get to the proper facilitates. Some people may fear getting tested because they are afraid of being near someone who does have the disease. They may fear the quarantine facilities and decide to self-quarantine. The Chinese government has arrested whistle blowers and citizen journalists who have made information about the disease public. The Chinese government may be concerned that the economy will suffer if the true effect of the disease is known, if they have been covering information up. Further supporting that the disease has spread faster and has been more deadly than China let on, when the city of Wuhan with 11 million residents was quarantined, fewer than 500 cases had been reported and fewer than 20 deaths (https://foreignpolicy.com/2020/01/20/wuhan-quarantine-virus-china-coverup-government-how-scared-should-you-be-of-the-wuhan-coronavirus/)
As China has found, keeping it secret and under-reporting, the numbers leads to the virus spreading more rapidly because people don't take sufficient precautions to protect themselves and others. The more it spreads the worse the economic impact. In the short term it can appear that the economy will benefit from not causing panic, but China has proven this wrong. One sick worker in a factory can shut down production. Sick people need to be encouraged to stay home. Educational institutions especially, because of their international students, should make it easy to work at home if a person feels unwell, students should not be forced to attend classes if they can do their work from home. If it continues to spread people should also be advised to avoid crowded places if they can and to wear masks if they must go to a crowded place. Sick people especially should wear masks to avoid infecting other and to protect themselves against picking up additional infections such as flu while their immune systems are already compromised.