Britain imposed tougher lockdowns across swathes of northern England after a rise in the rate of coronavirus transmissions, raising concerns that a second wave could sow yet more turmoil.

Britain reported its highest number of infections in more than a month on Thursday, as Prime Minister Boris Johnson spoke of a second wave in Europe and put people on alert about more quarantine restrictions.

More than 4 million people were ordered not to mix with other households in Greater Manchester, the biggest city in northern England, parts of West Yorkshire and East Lancashire, though they can still go to the pub and to work.

“The problem with this virus is that it thrives on the social contact which makes life worth living,” Health Secretary Matt Hancock told Sky. “I totally understand the human impact of this but unfortunately that is how the virus passes on.”

“We can see that second wave in Europe,” Hancock said.

Asked by the BBC if the UK was now entering a second wave, Hancock said: “It is not yet and we are absolutely determined to take the action that is needed.”

The measures were introduced hastily during the start of the annual Eid al-Adha “feast of sacrifice”, disrupting the celebration that marks the end of Ramadan for hundreds of thousands of British Muslims.

People in the areas affected were told not to socialise with other households at home or in gardens, or to meet with other households in pubs, restaurants, cafes, shops, places of worship or leisure venues.

But people are allowed to attend a pub, church or mosque with members of their own household. Those breaking the rules will face a fine of 100 pounds.

Official data showed 846 new positive tests in Britain - the highest number of daily infections since June 28.

Neil Ferguson, a leading epidemiologist at Imperial College London, said he was anxious about the planned return of schools after the summer break and cautioned that stricter controls could be expected later in the year as infections rise.

“We will have to roll back on forms of contact; reverse some of the relaxation,” Ferguson told the New Statesman magazine, though he added that he did not expect a nationwide lockdown.