In Britain, which has suffered the greatest number of virus deaths in Europe, Prime Minister Boris Johnson has walked a tightrope between scientific advisers who are pushing for another nationwide lockdown and members of his Conservative Party who warn that such a draconian response would wreck the economy.
On Monday, Mr. Johnson rolled out a three-tier system of restrictions. Though the government initially put only put hard-hit Liverpool in the highest-level tier, other cities, like Manchester, are likely to be added soon.
The opposition Labour Party and medical experts are urging Mr. Johnson to impose a two-week shutdown, which experts have dubbed a "circuit breaker," to arrest the virus, which is now spreading from the north of England across the country.
"You don't need to be a rocket scientist to look at that and realize you're going to end up with the majority of people living under more severe restrictions," said Graham Medley, a professor of infectious disease modeling at the London School of Hygiene and Tropical Medicine.
Other parts of the United Kingdom are already taking strong measures. On Wednesday, Northern Ireland announced it would begin a four-week lockdown, and close schools for two weeks. It is reporting an average of nearly 900 new daily cases this week, compared to just over 100 during the height of the first wave in mid-April.
"This is deeply troubling, and more steps are urgently needed," said Arlene Foster, Northern Ireland's First Minister, as she announced the new restrictions.
Wales announced that it would bar entry to people coming from other parts of the United Kingdom with high infection rates.