COVID-19: Making sense of all the numbers

CONFIRMED CASES

Confirmed cases are the number of people who have tested positive.

One of the stealthiest characteristics of the coronavirus is that it can be spread with little to no symptoms. This means that the number of people worldwide who are actually infected is probably much higher than the official confirmed cases.

If you have not been tested, you are not counted.

Viruses, including COVID-19, tend to spread at an exponential rate, which means they multiply really quickly. On March 6, the world had 100,000 confirmed cases, one month later there were one million, and if the virus continues to grow at this rate, this number could reach 10 million by May.

That is why governments in many parts of the world have imposed nationwide lockdowns to slow down the rate of infection or "flatten the curve".

CONFIRMED DEATHS

Reporting deaths is a sensitive process.

Every country has its own methods for reporting, which include reviewing a patient's medical records and informing family members before releasing any figures.

Leading infectious disease experts have already warned that, despite strict physical distancing measures, the world could still face hundreds of thousands of deaths - if not millions.

Just like confirmed cases, the actual number of deaths is almost certainly higher than what is being reported.

Several reports have also emerged of undercounting. These include many cases where people are dying at home despite showing unmistakable COVID-19 symptoms.

The case-fatality-rate (CFR) is the proportion of people who die out of those who test positive.

This makes COVID-19's mortality rate a moving target.

Every country has its own mortality rate. Italy's case-fatality-rate is about 12% while Germany's is 1%. The virus itself is not more potent in Italy, but rather the differences can be explained by how rigorously countries are testing and counting the number of infections and deaths. A country's age demographic and healthcare infrastructure have been shown to play a role in determining this number.

The infection-fatality-rate (IFR) is the proportion of people who die out of the actual number of people who were infected.

If 1,000 people have COVID-19 and only 100 of those test positive, then if 10 people were to die, the (IFR) would be 1% - much less than the case-fatality-rate (CFR), but still higher than the seasonal flu.

The infection-fatality-rate is the mortality rate most of us are actually looking for.

As several reports have suggested, COVID-19's infection-fatality-rate is probably lower than initially estimated, mainly due to many cases going undiagnosed.

CONFIRMED RECOVERIES

The overwhelming majority of people who contract COVID-19 get better. According to the WHO, the virus typically lasts about two weeks for mild cases and three to six weeks for serious cases.

It is important to remember that most coronavirus cases are mild.

Keeping an eye on recoveries should help avoid unnecessary global panic and help individuals better understand the risks to themselves and their community.

There is a lot of uncertainty in calculating this figure. So much so that Johns Hopkins University temporarily suspended its reporting of recovered cases citing "no reliable data source reporting recovered cases for many countries, such as the US" , before resuming its tally a few days later.

CONFIRMED ACTIVE CASES

If you want to know how many people are currently infected, you need to take the number of confirmed cases and subtract those people who have recovered or died from the virus.

Even if a country currently has a low number of confirmed cases, it is important to keep in mind that most countries show very similar traits in how the disease spreads. Initially, the numbers may seem small, but due to the virus's exponential nature, the numbers multiply quickly.

In an ideal situation, extrapolating patterns from countries with early outbreaks, including China, South Korea and Italy, would help other countries inform their respective response strategies. The problem is that, especially in the case of China, there have been accusations that the official figures underreport the number of cases.