After more than six weeks of a rigid national lockdown, Denmark says it has curbed the spread of the coronavirus variant first identified in Britain.

Danish health authorities — who are trying to sequence all positive coronavirus tests, giving them a detailed view most countries do not have — worried earlier that established methods of control might not work against the more contagious variant.

But new data suggests that at least at the beginning of the month, infection levels in Denmark were constant — not shrinking but not growing exponentially, as they had been in earlier weeks.

That’s hopeful news with implications far beyond Denmark, as the variant has been quickly spreading around the world. The Centers for Disease Control and Prevention estimates it will be dominant in the United States by next month.

But Denmark’s progress has been hard won, and officials stress it could be temporary.

Danish authorities said that as of Feb. 1, people infected with the B.1.1.7 lineage were passing it on to an average 0.99 other people.

“Although it is positive that the contact number is now around 1, the development must be interpreted with caution, as there may be variation over time, and it is too early to assess whether there is a stable trend,” Denmark’s State Serum Institute, the public health agency charged with monitoring the spread of the virus, said in a statement.

Danish researchers still think the strain is 20 to 50 percent more contagious than the original.

Because of the variant, Denmark has had a tight lockdown in place since late December.

Primary schools were partly reopened Monday, after being closed to in-person instruction since the winter holidays. But the rest of the restrictions remain in effect until at least Feb. 28, and some policymakers expect a further extension. Most businesses are closed, people have been ordered to work from home, and limits have been imposed on international travel.

Denmark has also had one of the more efficient coronavirus vaccine rollouts in Europe, though it is now waiting for a resupply of doses.

Danish leaders have emphasized that citizens should not relax, even though overall coronavirus case numbers have been dropping.

“Although the numbers on the surface look good in Denmark, the British mutation is simmering just below and will soon be the dominant one,” Danish Prime Minister Mette Frederiksen told reporters Monday as she visited a newly reopened school. “So we cannot do a major reopening in Denmark, although of course we would like to.” She said it would probably be a while before schools reopened further.

As of last week, the variant accounted for 27 percent of all coronavirus infections in the country, up from 20 percent the previous week, and researchers expect it will overtake previous mutations within weeks. But the slowed transmissions have bought the country some time.

The growth was visible in a separate estimate of the country’s overall viral reproduction rate released Tuesday. The rate rose to 1, meaning that overall cases are staying flat rather than shrinking.

The rise “is not unexpected when the share of B117 grows and when we have the season against us,” Danish Health Minister Magnus Heunicke wrote on Twitter, noting the new data. “Now it is important that the number is kept at this level when B117 becomes dominant. So stick to good habits.”

The new data on the viral mutations, which was released Tuesday, covers the week up to Feb. 1. There is a delay because it takes time to sequence the genome of each positive case of the coronavirus.

Public health officials warned that preliminary analyses of data since Feb. 1 suggest that the new variant may again be increasing.