COVID-19 is one in a 100 year tragedy and there is understandably a lot of fear. There are a lot of numbers flying around and too often, for the sake of a great news story, a lot of misinformation. Removing the human element of this tragedy for a moment, here is what we can tell from the available numbers.
Growth Rate
The daily global growth rate of ‘reported’ cases is typically between 10 and 20%. It took five days for daily reported new cases to double from 10,000 to 20,000, and then another five days to double from 20,000 to 40,000, so the growth rate is constant.
Outside of China and South Korea, this is the same in the vast majority of countries, from those more advanced, such as Italy and Spain, to countries like Australia where the virus is just starting to take hold. Yesterday’s daily growth rate was fairly typical (numbers rounded):
Global total (excluding China): 388,000
Global growth: 45,700 (12%)
Australia total: 2,015
Australia growth: 380 (19%)
WA total: 205
WA growth: 30 (12%)
These numbers are of course significantly under-reported, as a large portion of the community are asymptomatic. This is further reinforced by the reported ‘closed cases’ death rate of 16%, which conflicts with the WHOs latest estimate of 3 - 4%.
Trajectory
Country-wide lockdowns seems to be slowing the growth rate in countries like China and South Korea, but having limited impact in countries such as Italy and Spain. However, the numbers are difficult to validate and there is a significant lag affect.
If the growth rate was to continue at a conservative 10% per day, in 30 days the number of reported cases will be as follows:
Global: 6.8 million
Australia: 35,000
WA: 3,600
This is why governments and health organisations are afraid and taking such extreme measures.
Mortality Rate
The reported mortality rate seems to vary radically between countries, and while variance is expected, this is more likely a reflection of testing and reporting.
Early estimates were 1 to 2%. The last announcement from WHO on March 6 estimated a mortality rate of between 3 - 4% (this is more than 30 to 40 times the mortality rate of the seasonal flu), but even WHO admits there is great difficult in estimating the mortality rate in the midst of a pandemic. WHO’s early estimates for SARS was less than 3% and it ended up being closer to 10%.
If reporting was accurate, the best estimate would be the number of deaths as a percentage of closed cases. However, this is only as accurate as the total number reported and significantly inflated by under-reporting the number of infected. The current numbers indicate a mortality rate of 16%:
Cases with an outcome: 135,000 (84%)
Deaths: 21,200 (16%)
Recovered: 113,800 (84%)
If the 3 - 4% mortality rate is accurate, this would indicate the true number of cases with an outcome is approximately 4.5 times this number e.g. 540,000.
Keeping Up to Date
A useful site for keeping up to date on desktop and mobile is worldometers.info. They run a live feed and reset the daily reports at GM0, which is 8am Perth time. The sources seem to check out and they feed a lot of content direct from WHO.
