How a Champions League match might have triggered the spread of Covid-19 in Lombardy region

On March 18, a convoy of military trucks left Bergamo cemetery carrying hundreds of coffins. That image has become one of the symbols of the Covid-19 epidemic that hit Italy. What happened exactly in the most affected province of Italy has long remained a mystery. INTWIG – a Research and Data Analysis Agency based in Bergamo – tried to solve it.

The mortality analysis

In mid-March, INTWIG started analysing data on excess mortality in Lombardy region during the Covid-19 pandemic. Comparing the deaths with the average number recorded over the same period in previous years, the Agency found out that the victims of the new coronavirus were much more than those reported officially. The comparison conducted on each municipality showed that the deaths linked to the SARS-CoV-2 virus in the province of Bergamo were actually over 6.000, twice as many as those officially declared (3.100). Based on an infection fatality rate of 1.6, INTWIG estimated that about 36% of the inhabitants of the province had contracted the virus, much more than other areas of Lombardy.

These data have recently been confirmed by a research conducted at the Mario Negri Institute, and published in the EbioMedicine journal (The Lancet Group). According to the authors, 38.5% of residents in the Province of Bergamo may have contracted the SARS-CoV-2 virus, a figure that far exceeds the estimates of New York (19.9%), London (17.5%) and Madrid (11.3%). Based on these data, the Province of Bergamo would thus be one of the most affected areas in the world.

The analysis conducted by INTWIG also allows to accurately reconstruct the virus spread and its timing. The study shows that in some municipalities the mortality had exceeded the average of previous years already in January, as in the case of Nembro. The analysis therefore confirms the hypothesis that the Covid-19 outbreak in Lombardy region started unnoticed at the beginning of the year.

What happened in Bergamo? The role of the Champions League match

Due to technical reasons, on February 19, Atalanta – a soccer club based in Bergamo – played its Champions League match against Valencia at San Siro stadium, in Milan. The match took place two days before the first Italian case of coronavirus had been officially diagnosed in Codogno, another small town in Lombardy. To understand if the event may have unintentionally triggered the spread of the virus, INTWIG – along with the journalistic TV program Report and the local newspaper Bergamonews -carried out a survey among Atalanta’s supporters.

The survey was answered by 3,402 people that live in Bergamo area and were at the stadium that night. According to the results, more than 1/5 of the supporters surveyed (7,800-8,200 people) said they developed symptoms within two weeks after the match. When part of them got tested for the virus, they resulted positive to Covid-19.

The analysis seems to confirm the hypothesis that the Champions League match may have been a “super-diffuser event”, allowing the virus to infect thousands of people. Most likely, the major part of infections took place during the transfer from Bergamo to Milan, the pre-match gatherings and the celebrations for the victory. How the movement of 36 thousand people may have affected the spread of the virus is also clear from the respondents’ answers: most of them traveled to Milan by bus (19%) or by cars shared with other people (67%).

Today, we know that events that host a great density of people who speak aloud, shout and sing are fertile ground for the transmission of Covid-19.

A further confirmation of the hypothesis was found by the analysis of the tickets sold. The study shows that most of the fans that bought and used the tickets live in the urban area of Bergamo and in the northern valleys, while people resident in the southern part of the province were relatively less present at the stadium.

These data confirm therefore that the spread of the virus moved from towns such as Nembro and Alzano (1.200 fans present) to the urban area of Bergamo and Brembana Valley, sparing the areas of Treviglio and Romano di Lombardia that are located in the south of the province.

The effects on the second wave

Summarizing the events recalled so far:

– at the beginning of the year, the virus arrives untraced in Italy and begins to circulate in the areas of the lower Seriana Valley;
– on February 19, the soccer match Atalanta-Valencia takes place: a unique event where 36 thousand people move together without practicing any social distancing;
– after the match, more than 1/5 of the fans develop symptoms related to Covid-19.

What is the consequence of this perfect storm?
On March 6, two weeks after the match, the mortality of the province of Bergamo exceeds the average of deaths registered in previous years, especially in the areas of lower Seriana Valley, Brembana Valley and Bergamo city.

What is the dynamic of the contagion?
A possible answer can be found in the series of maps that shows the trend of the contagion from early March until June. The contagion quickly expands from the municipalities mentioned above to the entire northern area of the province, exactly the area where more tickets per 1.000 inhabitants were sold.

Eight months after that tragedy, however, the data leave now some space for hope, showing that those same areas seem to have acquired greater protection from the virus. The comparison of the regional contagion data related to the first and second wave, highlights how today the virus affects more the western area of Lombardy, sparing the areas that were so dramatically hit at the beginning of the year.