BERLIN — By the time German health officials in the state of North Rhine-Westphalia had confirmed the state’s first case of the coronavirus, the patient was already so ill that he had been placed on a respirator. He was in no position to help authorities, who urgently needed to retrace his steps to try to stop, or at least slow, the virus from spreading.
Already, they had lost time. The virus has a 14-day incubation period, so they knew that the man, who was hospitalized on Monday, could have infected many more people before he started receiving care, all of whom were now in a position to pass the virus across Germany’s most populous state and beyond.
“We were faced with a puzzle that we thought had 10,000 pieces, only to realize it has endless pieces,” Ulrich Hollwitz, a spokesman for the Heinsberg district where the man lives with his wife and two children, said on Thursday. “Where was he and when? Who did he have contact with and how close? We had to start working like detectives.”
What the authorities were able to discover was worrisome: The man had not traveled to China, or to other virus hot spots like Italy, nor was he known to have come in contact with someone confirmed by the authorities to have been infected.
If the mystery of how he contracted the virus could not be solved, the risk of its spreading widely would rise considerably, with authorities losing the capability to track, and isolate, people who could infect others.
So shortly after his test results came back positive late Tuesday, officials in the Heinsberg district jumped into action. First, they turned to the man’s wife, who by Wednesday morning had also tested positive for the virus, pressing her for as much information as she could give.
Unable to identify the man’s source of infection right away, authorities turned their focus to anyone in the couple’s immediate sphere, who were ordered to stay home. Because she was a preschool teacher and the couple had two children of their own, officials ordered all district schools and preschools closed for the remainder of the week.
The couple’s children, who have shown no symptoms of illness, were sent to stay with their grandparents and told to remain in isolation.
Fifty district employees were assigned to a crisis team and specialists were sent in from the state’s health ministry and from Germany’s center for disease control, the Robert Koch Institute.
Then began the work of retracing the man’s steps, in hopes of figuring out how he had contracted the virus.
“We are pretty sure that the man was the first to be infected in the chain, but we don’t know from whom,” said Karl-Josef Laumann, the health minister for North Rhine-Westphalia. “It is a problem that we don’t know the start of the chain of infection, which could lie beyond North Rhine-Westphalia.”
In the weeks leading up to the man’s illness, the couple had been active in their jobs and communities, making a short visit across the border to the Netherlands and, on the weekend of Carnival, taking part in a local festival with hundreds of others from around the area, his wife said.
German Carnival parties involve people packed tightly together, drinking and dancing, hugging and kissing, meaning that any of the 300 people who attended could have been infected.
“There is a lot of close contact, in all directions,” said Mr. Hollwitz, the district spokesman. “We were facing a huge task, even though we knew we wouldn’t find everyone. We had to do our best to stop the chain of infection.”
Anyone who had attended the Feb. 25 event in the town of Langbroich Gangelt was ordered to remain at home until the end of the week, as was anyone who had been in close contact with the couple or their family.
“With every person we reached who he had been in contact with, we learned more. Everyone was able to add to our knowledge,” Mr. Hollwitz said. “It was as if we started with a very blurry photo and with each person contacted, we had an additional pixel that made it sharper.”
By Wednesday evening, three more men and a woman, all of whom had been in contact with the infected couple, had tested positive for the virus.
Germany now has more than two dozen cases, but authorities have decided not to impose full lockdowns on cities or towns, instead relying on people to exercise caution and follow orders for isolation at home.
“We all saw that in China they closed everything off, and the number of cases still went up,” said the district administrator, Stephan Pusch. “We are a free country and we have citizens who can be reached, who react, as far as I know, to our recommendations and I think that for our country, that should be our point of orientation.”
The German government has begun registering anyone arriving in the country by air or by sea, and will soon do the same for those arriving over land, as part of efforts to make it easier to trace — and shut down — any future chains of infection.
They cite the apparent success of halting the spread of the virus last month in Bavaria, where a woman from China infected a German employee in a factory in Stockdorf. The day after the employee fell ill, the company, the car parts manufacturer Webasto, closed its shop for two weeks. All employees and their family members were ordered to stay home.
The measure, although unpopular in the town, succeeded in stopping the spread of the disease, officials said.
By late Thursday in the Heinsberg district, 14 more people from the infected man’s town had tested positive for the virus. None of the new cases were serious enough to require hospitalization, and they were all ordered to remain at home, in isolation, as the search for the source of the infection continued.
“The man had business contacts beyond the state,” Mr. Laumann, the state health minister said. “But the good thing is that all of the new infections that we have so far come from people around this couple.”