The UK should steel itself for a “difficult autumn” and “hard winter” of illnesses because people have lived for an unusually long period without exposure to respiratory viruses, one of the country’s top medics has warned. Dr Susan Hopkins, the head of Covid strategy for Public Health England, said population immunity to viruses other than Covid-19 could be lower than usual and that a surge in flu was probable. She said the NHS must be better prepared than it was last autumn, when new, faster-spreading variants of coronavirus emerged forcing the country into lockdown for the third time. On Monday all pupils in England will return to school in the first step of the government’s easing of lockdown, which some scientists have warned against, arguing that it could push the R number for coronavirus to riskier levels. Speaking on the BBC One’s The Andrew Marr Show Hopkins said: “I think we have to prepare for a hard winter, not only with coronavirus, but we’ve had a year of almost no respiratory viruses of any other type. And that means, potentially the population immunity to that is less. “So we could see surges in flu. We could see surges in other respiratory viruses and other respiratory pathogens.” A record number of people, about 30 million in total, were invited for a free flu jab last autumn as ministers feared it would add to strains on the NHS. Flu kills about 11,000 people in England every year, with many more having to be treated in hospital because of it. “It’s really important that we’re prepared from the NHS point of view, from public health and contact tracing, that we have everything ready to prepare for a difficult autumn,” she said. “We hope that it won’t occur and it will be a normal winter for all of us.” Preparing “for worst-case scenarios” was a key part of her role as a government adviser, she added. “It doesn’t mean that they’ll necessarily happen, but my job is to make sure that we have options available for the country in case things are not as satisfactory as we’d all like them to be,” she said. Hopkins said it was “highly unlikely” that a new Covid variant would derail the plan to start easing England’s lockdown “for the next three to five weeks”, but added: “We’ll need to monitor carefully as new strains come into the country from around the world. “We’ll need to be very ready for an autumn that could be challenging as these variants are there.”