An evangelical church service became a focal point for the coronavirus epidemic in France.

Reuters - At the altar of a large evangelical church, the leader of the gospel choir began an evening of prayer and preaching: “Let us celebrate the Lord! Are you feeling joy tonight?”

"Yes!" shouted the hundreds of people gathered at the Christian Open Door church on February 18. Some of them traveled thousands of kilometers to participate in the week-long gathering in Mulhouse, a city of 100 inhabitants on the border of France with Germany and Switzerland.

For many members of this flock, which includes people from all over the world, the annual celebration is the highlight of the church calendar.

This time, someone from the congregation was carrying the coronavirus.

The religious service was the start of the largest coronavirus cluster in France – one of the hardest-hit countries in northern Europe – to date, the local government said. Around 2.500 confirmed cases have been linked to the service. Churchgoers unknowingly carried the disease caused by the virus to Burkina Faso in West Africa, to the Mediterranean island of Corsica, to Guyana in Latin America, to Switzerland, to a French nuclear power plant, and to the factories of one of Europe's largest car manufacturers.

Weeks later, Germany partially closed its border with France, suspending a 25-year-old free movement pact. The cluster of churches was a key factor, two people familiar with the German decision told Reuters. Church leaders told Reuters that 17 members of the congregation had died from complications related to the disease.

Other religious gatherings have been linked to the spread of the virus: a large church in South Korea triggered more than 5.000 cases there. This story, told to Reuters by members of the Christian Open Door congregation and officials involved in dealing with the outbreak, is a testament to the speed and ferocity of coronavirus infection. As public health administrators were still preparing for the coronavirus, the disease was operating on its own timetable, quickly overtaking any measures they could implement.

When worshippers gathered on a Tuesday evening in the church, a former shopping center converted into a 2.500-seat auditorium, the disease seemed remote. France had 12 confirmed cases, according to data from the World Health Organization (WHO). There were none in the Mulhouse area.

France, like other northern European governments, did not impose restrictions on large gatherings. There was no hand sanitizer for congregations to clean their hands, nor elbows instead of handshakes.

"At the time, we saw the coronavirus as something very distant," said Jonathan Peterschmitt, son of the senior pastor and grandson of the church's founder. His father, Samuel, was unavailable for an interview because he was disgusted by the virus, his son and a church spokeswoman said.

The day after the first church-related case was identified on February 29, public health authorities followed standard protocol and located the people the carriers had been in contact with to contain the spread. Using a list provided by the church—which public health officials said had fully cooperated—they contacted the staff at the children's daycare center during the gathering.

At that point, health inspectors realized it was too late. Some daycare workers were already sick, according to Michel Vernay, an epidemiologist with France's national public health agency in eastern France.

"We were stunned," said Vernay. "We realized we had a ticking time bomb in front of us."