Leaders across much of northern England have pleaded with residents to “do their bit” to prevent a second wave as the number of Covid-19 cases rises. Representatives of every local authority in the north-east wrote an open letter to lambast the “significant minority” of residents having house parties and ignoring the rules, saying they were “deeply concerned” at the increasing number of positive coronavirus cases, particularly among young adults. They also criticised the “reckless and selfish behaviour” of those who developed symptoms, took a test and then went out and infected others before getting their results. The region is now recording an average of 80 cases a day – twice the number last week, with the figure expected to rise in coming days. Middlesbrough’s independent mayor, Andy Preston, issued a video message on Tuesday warning: “Right now our rate per 100,000 is still too high, it’s in in the 40s, we need to bring it down. We need to avoid a government-imposed lockdown that will damage jobs and damage mental health.” On Monday he was criticised for not wearing a mask when visiting a shopping centre – he said he had forgotten and put one on as soon as he realised. Steve Rotheram, mayor of the Liverpool city region, issued a statement saying there had been a “worrying rise in cases of coronavirus” there over the past week. “I know that nobody wants to see a local lockdown like we’ve seen in other areas, so please keep taking every precaution to stop the spread,” he urged. Andy Burnham, the mayor of Greater Manchester, tweeted the latest estimates of the R number across the country, showing rates were probably increasing in most regions of England. They show a “changed and challenging picture”, he said. Most of Greater Manchester remains subject to enhanced restrictions banning gatherings in private homes or gardens. In Bolton, the worst affected area, restrictions were further tightened on Tuesday, with all pubs and restaurants now allowed to serve takeaway only and ordered to close at 10pm. On Tuesday, the infection rate per 100,000 people in Leeds remained high at 47.3. The city’s director of public health, Victoria Eaton, said the pattern of infection had “changed completely” in recent weeks. After battling community clusters in deprived areas of the city with high-density housing between the end of July and early August, the council began to see a widespread surge in cases among 18 to 34-year-olds – including in affluent areas – which coincided with A-level results day. “It was partly about returning travellers from Europe. It was partly about house parties and bars, so younger adults socialising,” said Eaton, adding that the only age group not affected by increasing cases were the over 65s. “There is this sense of reasonable complacency, that even though cases are rising, this is the group of people that are least likely to be severely affected,” said Eaton. “But we know from what’s happened in places like France that that spread will spread will start to affect more vulnerable people and older adults as we move into autumn and winter.” In their statement, the north-east leaders said residents “all have to do our bit and to play our part if we are to prevent a potential second wave. The impact that would have on our health service and the possibility of an economically-damaging lockdown would be devastating.” “People who have symptoms or are asked to do so by the health protection teams must book a test and self-isolate until they have their results,” said the leaders, who represent Newcastle, Sunderland, Durham, Gateshead, North Tyneside, Northumberland, South Tyneside and the North of Tyne combined authority. “Don’t assume, if you are a contact, that a negative test means you are OK – it doesn’t; you could be incubating the virus. If you are asked to self-isolate, it is really important that you do so whatever your test status at the time. “We have seen cases where individuals with symptoms have had a test, then gone out and infected others before getting their results – reckless and selfish behaviour.” The leaders warned non-compliant businesses that they would be shut down and issued a stark message for people flouting rules on gatherings. “A significant minority believe it is OK to have house parties, hold events with unregulated crowds, ignore the rules – well it isn’t,” they wrote. “Household transmission remains the biggest danger. By not following the guidance, advice and legislation you are at greater risk of spreading the virus to your own family, which as we have seen can lead to tragic consequences. None of us yet know the long-term health impact of Covid 19, while the full social and economic consequences are also yet to play out.”