Calculations made on the basis of redundant mortality data and laboratory tests showed more reliable mortality of the SARS-CoV-2 virus.
Italian scientists Gianluca Rinaldi and Matteo Paradisi have published an article in the medRxiv preprint archive about the largest and most detailed study of coronavirus mortality in the first 40 days of the Italian pandemic. The study was carried out in a part of Lombardy, an administrative area of the country that was severely affected by a coronavirus. The study area covered 10 localities with a total population of about 50 thousand people.
Paradisi and Rinaldi did not use in their work official statistics of mortality, as it is in many cases incomplete or distorted. Instead, the scientists used SARS-CoV-2 testing statistics. It is the data from mass tests that make it possible to estimate more accurately the scope of the pandemic and the actual mortality of the pathogen.
The study area was the epicenter of the COVID-19 outbreak throughout Italy. On 21 February, the region’s borders were completely closed and strict quarantine was imposed in all 10 towns. It was this date that Paradisi and Rinaldi took as the starting point for the data.
Having collected data on mortality and the sex and age distribution of the dead in the region from late February to April 4, researchers compared this information with similar statistics for the same period in the previous five years. It turned out that in 2020, five times as many people died in these 40 days as usual: 341 vs. 70 on average. At the same time at the very beginning of April there was practically no excessive mortality.
Then the statistics were analyzed on the results of blood tests, which were carried out in the region after the removal of strict restrictive measures. The degree of infection with the virus in the studied region was about 40%, while in some settlements it reached 80%. Based on these data Paradisi and Rinaldi found that coronavirus lethality is 1.29%. At the same time, in the group of people over 60 the parameter is 4.25%.
Interestingly, this figure almost coincides with the mortality rate calculated for one of the world’s first COVID-19 hotbeds, the cruise liner Diamond Princess (1.3%). But in that case, the researchers dealt with a relatively small sample (about three thousand tested, 712 infected, and 13 deaths). In addition, there were a large number of elderly passengers on the liner.
A recalculation based on data from Diamond Princess for the Chinese population showed that the estimated mortality rate for this country was 0.6%. The results of the new study show that this number is twice as high. Of course, it is worth considering the fact that the Italian population is one of the “oldest” in the world. However, on average, in all countries coronavirus with a bad scenario can take the lives of about 1% of citizens.
Statistics also show that it is hard quarantine that is the main effective measure to prevent a pandemic. The further away from the Italian epicenter, the lower (with some exceptions) were the rates of infection and lethal outcomes. These same measures, however, did not create collective immunity in the population; many who did not become ill during the current outbreak may catch coronavirus during the next waves of the pandemic. So the total number of deaths from COVID-19 will depend on how soon an effective vaccine is created or how effective drugs are found against the virus.