The U.K. government has announced it is moving to the next phase in its plans to combat the coronavirus outbreak in the country. Following a meeting of the government’s emergency planning committee Cobra, the country has formally moved from a “contain” standing to its “delay” phase.

Prime Minister Boris Johnson announced the move at a press conference Thursday. The news came a day after the World Health Organization officially classified the coronavirus outbreak as a pandemic.

“We’ve done what can be done to contain this disease but it’s now a global pandemic. This is the worst public health crisis for a generation,” said Johnson. “This disease is going to spread further. This is now not just an attempt to contain the disease but delay its spread.”

Measures such as closing schools and a ban on public gatherings, as have been seen in a number of countries around the world, have not been implemented at this time. “The scientific advice is that this could do more harm than good,” said Johnson, although he did say the government was advising against the elderly from going on cruises and against any international school trips.

Johnson said: “The most important task will be to protect our elderly during peak weeks. The most dangerous period is not now but some weeks away.”

Chief medical officer Chris Whitty said a new request to the public were that “from today to ask anybody that has a cough that is persistent or new, or who has a temperature of 37.8 degrees to stay at home for at least seven days.”

“It helps to protect elderly or more vulnerable people,” said Whitty, explaining it would also help to lower the peak of the epidemic and delay the peak, reducing pressure on Britain’s National Health Service.” Whitty explained the seven-day period was due to the science showing the virus seemed to have its maximum transmission in its first days and that after seven days the majority of people would no longer be likely to pass it on.

“It is no longer needed to identify every case, so we will pivot testing capacity to identify people in hospitals with symptoms to ensure they don’t pass it on,” added Whitty. He also said there would no longer be any geographical limits for testing but testing would be based on symptoms and severity not travel history.

Johnson said that in the next few weeks measures would likely go further and ask anyone in a household where one person was showing symptoms that all in the household should self-isolate. He also said they would continue to consult and consider whether to impose a ban on major public events such as sporting fixtures and that more advice would follow in the coming weeks.

“At all stages we have been guided by the science and we will do the right thing at the right time,” said Johnson. He said there was “no escaping the reality” that the coronavirus epidemic would cause disruption for some months to come.

Whitty said regarding school closures the two reasons to do so were the protection of children and to impact the epidemic. He said one silver-lining in this particular infection was that it seemed to have a milder impact on children and that closing schools has a big knock-on effect and that doing so could potentially put older people at greater risk.

Whitty said the worst case planning scenario was up to 80% of the country being infected but said that was “an entirely speculative number.”

Chief scientific advisor Patrick Vallance said the peak was expected to be 10-14 weeks away and that the U.K. was probably about four weeks behind Italy. The U.K. has a four-stage plan to tackle the virus: contain, delay, research, mitigate.

The U.K. is currently the only European country exempt from a 30-day suspension of all travel from Europe to the U.S. announced by President Trump on Wednesday.