There was some encouraging, if not exactly good, news out of Italy Thursday as the rate of new infections of the coronavirus slowed in the country that has been overwhelmed by the virus. To be clear, the number of new cases continues to grow daily in Italy, but the growth rate has come down, hopefully signaling that Italy’s lockdown measures are finally taking hold on curbing transmission. The virus’s spread, however, has accelerated elsewhere in the Mediterranean with Spain’s death toll skyrocketing to more than 4,000, surpassing China’s number of reported fatalities.

There are numerous causes for the spread of the coronavirus that will surely become clearer as we go along and, more realistically, in the years to come. Living in open societies and the capacity to hopscotch freely around the world are two innocent bystanders of the coronavirus; there were also missed warning signs and opportunities to detect and contain the virus’s spread before it took off. The world is social distancing now, holed up apart, as are both Italy and Spain. But it wasn’t long ago, just last month in fact, that both societal openness and unheeded warnings collided on a soccer pitch in Italy.

On Feb. 19, tens of thousands of fans of Atalanta, the northern Italian city of Bergamo’s hometown team, poured into neighboring Milan, which was playing host to the club’s Champions League match against Spanish club Valencia. It was Atalanta’s first-ever trip to the knockout round of Europe’s most prestigious club competition, and the city of some 120,000 residents was euphoric. Now, looking back on it, for Bergamo Mayor Giorgio Gori the match, which Atalanta won 4–1, feels very different and, he says, is one “among the sad explanations” for what would unfold over the next weeks, as the coronavirus engulfed Bergamo, making it the new epicenter of the virus—the hardest-hit city in the hardest-hit Italian province of Lombardy.

“Some 40,000 Bergamo inhabitants went to Milan to watch the game. Others watched it from their homes, in families, in groups, at the bar,” Gori said Wednesday. “It’s clear that evening was a situation in which the virus was widely spread.” It’s unlikely that it was the only cause of the virus’s explosion, but it will take time to unravel the unknowns about the pandemic’s spread. What we do know is Atalanta fans piled in cars, buses, and on trains that evening to make the 30-mile trip to Milan to cram into the San Siro stadium against the team from Spain. In retrospect, the match was “a biological bomb,” says the head of pulmonology at a hospital in Bergamo.

At that point in the pandemic, Wuhan had already been on lockdown for weeks, and there were confirmed cases as far as the U.S. The virus still felt distant somehow despite that in all likelihood it was already circulating in Italy and beyond. “It’s probable that there were several major triggers and catalysts for the diffusion of the virus, but the Atalanta-Valencia game could very well have been one of them,” immunologist Francesco Le Foche told Italy’s Corriere dello Sport. “With hindsight, it was madness to play with a crowd present, but at the time things weren’t clear enough. It’d be unthinkable now.”

Four days after the match, Italian authorities locked down cities across the Lombardy region. Schools were closed and sporting events canceled. Nearly a month later, with the virus now in full swing in northern Italy, Atalanta still traveled to Spain on March 10 for the second leg of the tie. Before an empty stadium, Atalanta won again to advance to the Champions League quarterfinals, a round of the competition that looks increasingly unlikely to ever be completed. Last week, Valencia said a third of its players and coaches had tested positive for the virus since the match had taken place.

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