COVID-19 case fatality rates

Why do fatality proportions differ between countries?

If 1,000 people became infected with the novel Coronavirus, how many people may die?

This article looks at the COVID-19 case fatality rate. I also look at why this proportion differs between countries.

Challenges and caution

Estimating the deadliness of a new virus is challenging.

In opening remarks on 3rd March, Dr Tedros Adhanom Ghebreyesus (WHO Director-General) said:

Globally, about 3.4% of reported COVID-19 cases have died. By comparison, seasonal flu generally kills far fewer than 1% of those infected.

At that time, dividing total deaths (3,110) by total number of confirmed cases (90,893) gives 3.4%. On 29th January, that proportion was around 2%.

As of 9th March 2020, Johns Hopkins University states there are over 113,000 COVID-19 cases. The total number of deaths was about 4,000.

We should treat the case fatality rate with caution during an epidemic. Two competing biases affect this proportion: undetected cases and future deaths.

Undetected cases

The standard calculation uses the number of infected people. Usually, this is the recorded number of patients who have the virus.