After data compiled by Johns Hopkins University appeared to show Italy has the third-highest Covid lethality rate in the world, calculated at 3.8 percent, some Italian media reports have suggested this may mean the virus is somehow “worse”, or more lethal, in Italy than elsewhere.

But some Italian health experts questioned the study’s findings, warning that the apparent lethality rate figure “means nothing” because of the way it is calculated.

While Italy is no doubt recording a high number of Covid-related deaths at the moment, does it really have one of the world's highest lethality rates?

Data expert Matteo Villa, a researcher at the Italian Institute for Political Studies in Milan, slammed suggestions by the Italian press that the virus is more lethal in Italy as “terrible”.

“They are using the apparent mortality rate, which as we know means nothing, to argue that in Italy the virus is worse than elsewhere,” he wrote on Twitter.

So what is the “apparent lethality rate”, and what’s the problem with it?

“The index is calculated on the basis of the ratio between deaths and number of positives, and everyone knows that during the so-called first wave, the number of people traced as positive in Italy, the first Western country hit, was dramatically underestimated,” Alberto Zangrillo, Vice Rector of the San Raffaele University Hospital in Milan, said in an interview with Italian news agency Adnkronos.

Italy’s apparent lethality rate (tasso di letalità apparente) in April was estimated at around 12 percent, a figure which researchers said was “almost impossible”. Limited testing at the time was thought to be skewing the figures.

While patients in a serious condition were being tested, it's thought that milder cases often went undetected until testing was later expanded.

Because this “assumed” lethality rate has been viewed as unreliable from the beginning, it has been little-used by researchers in Italy and is not usually mentioned at the health ministry’s press conferences about the coronavirus situation.

Instead of the assumed lethality rate, Italian researchers often look at the “excess” mortality rate to get an idea of what a more plausible number of Covid deaths is likely to be.

READ ALSO: Italy recorded more than 11,000 'excess deaths' in March

A recent report from the Italian Health Ministry showed the total number of all deaths in the country (not only those from Covid) is far higher than the usual figure recorded at this time of year.

The number of “excess” deaths is derived by comparing the number of deaths in Italy in a recent period to the statistical average for that period over the preceding five years.

At the moment, Italy is recording the highest death toll in Europe.

Last week, when a Covid-19 death was recorded in Europe every 17 seconds according to the World Health Organization, Italy had the highest toll on the continent with 753 victims in one day.

The worst-ever daily toll in Italy was 969 deaths, on March 27th.

On Monday Italy joined the United States, Brazil, India, Mexico and the United Kingdom in passing the symbolic 50,000-death mark.

More than 12.000 of those were within the previous 30 days alone.

Why is Italy seeing so many Covid-related deaths?

Health experts say the country’s aged population is one of the main factors.

“In Italy, the percentage of over-70s is 17%, compared to about 10% in the rest of Europe,” Zangrillo said. “And it is known that Sars-CoV-2 affects especially the elderly population in a lethal way.”

Villa explained that, in a way, this does mean that in Italy the virus “is worse than elsewhere”.

“We are second in the world for risk of death, just after Japan and just above Greece, Portugal and Germany.”

“But it is because we are old.”

“Obviously the number of Covid-19 deaths is an interaction between the risk of death and the frequency of contagion of the people most at risk,” he added.

“And it also depends on the saturation of the hospital system.”

Instead of comparing Italy’s data with that from the US, UK, or most other European countries, Villa says we should be comparing Italy with “Japan and Germany; countries with almost identical risks.”