A senior cabinet minister in the UK said on Sunday that the country could remain under lockdown for “a significant period” because of the coronavirus pandemic.

Michael Gove, who is in charge of the cabinet office, would not speculate on how long this might be, but Professor Neil Ferguson of Imperial College London, the government’s leading epidemiology adviser, said the lockdown could last initially until June.

Britain has reported 19,522 confirmed cases of the disease and 1,228 deaths.

The statement from Gove came as Prime Minister Boris Johnson wrote a letter to every single household in the land — 30 million in all — saying: “We know things will get worse before they get better.”

“But we are making the right preparations, and the more we all follow the rules, the fewer lives will be lost and the sooner life can return to normal,” added Johnson, who is in self-isolation at Downing Street after testing positive.

The lockdown was imposed partly as a result of modelling — still an inexact science — from Ferguson who had warned the government that without a lockdown, the death toll in the UK could be 250,000.

Ferguson has now told The Sunday Times: “We’re going to have to keep these measures (the full lockdown) in place, in my view, for a significant period of time — probably until the end of May, maybe even early June. May is optimistic.”

Gove declined to predict exactly how long the instructions to stay at home could last, saying the date the virus peaked would depend on how people behaved.

Asked on the BBC’s Andrew Marr Show how long the measures might go on for, Gove said: “So I can’t make an accurate prediction but everyone, I think, does have to prepare for a significant period when these measures are still in place. It’s not a fixed point, a date in the calendar, it is something that all of us can affect by our actions.”