# Coronavirus: Why it’s so deadly in Italy

## Demographics and why they are a warning to other countries

As we study the numbers on the coronavirus cases and the deaths related to COVID-19, a similar question comes up again and again:

Why is the coronavirus causing so many more deaths in Italy than in other countries?

This question relates both to the absolute number of deaths , which is currently exceeded only in China, and to the case fatality rate, which has risen to 6.6% and exceeds any other country in the world.

# The cases behind the case fatality rate

Let us assume every country is equally capable of counting the numerator of the CFR, the fatalities due to COVID-19, and will report them accurately; an assumption that is tolerable if we focus on non-authoritarian high-income countries. What do we then need to know about the denominator, the confirmed cases? The strongest predictors of fatality due to COVID-19 are age and pre-existing conditions of the infected. The number of pre-existing conditions is positively correlated with age, so let us for simplicity only look at the age of the confirmed cases. Clearly, because age is so predictive of death by COVID-19, comparing the case fatality rates across countries only makes sense if the underlying cases of coronavirus have approximately the same age across countries.

# Which CFR is unusual — Italy’s or South Korea’s?

An obvious question that follows is: Why do these age distributions look so different in the two countries? Many people have already pointed out that Italy has an older population than South Korea. The higher Italian CFR might therefore reflect a higher likelihood that an old person becomes infected with the coronavirus simply because there are more old people among the Italian population. We can easily check the plausibility of this argument by comparing the age structure of the coronavirus cases with the age structure of the total population for both countries. The population data are from the United Nations’ World Population Prospect 2019.

# Looking beyond Italy and South Korea

From these two rather polar-opposite cases of Italy and South Korea, what can be learned for other countries? Age aggregates for a subsample of the German confirmed cases of coronavirus have been published by the Robert Koch Institute, which is a German federal government agency responsible for disease control and prevention. Let us assume the subsample is representative. The age aggregates are not the same as in the Italian and Korean data, but cases can still be allocated to two groups: those younger than 60 years and those 60 years or older.

# South Korea provides a useful estimate of the CFR — but no guarantee

We can learn something more that is potentially very useful from the Korean statistics. We have seen above that the age distribution of the confirmed cases corresponds rather closely to the age distribution of the overall population in South Korea if we subsume everyone below age 30 into one group where almost nobody dies from COVID-19. At the time of reporting, 50 of the confirmed 7,134 people infected with the coronavirus had died, implying an aggregate CFR of 0.7%. Since then, the Korean CFR has been creeping up to 0.89%. Hence, 1% seems to be a reasonable estimate of the case fatality rate in a high-income country (!) in the absence of any major failures of the hospital and care system (!). This 1% CFR estimate is close to what Dr. Jeremy Faust has been suggesting based on the Diamond Princess cruise ship case.

## Witnessing the Spread of Coronavirus Through Airports and Culture

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