New flu strain that infects half the country and costs economy £2trillion is one of biggest future risks to Britain, health chiefs predict

By KRISTINA WEMYSS, GENERAL NEWS REPORTER Published: 16:55, 11 June 2026 | Updated: 16:55, 11 June 2026 A new flu strain that could infect half of Britain and cost the economy £2trillion is among the biggest risks the country faces, health chiefs have warned. The imagined variant would be transmitted quickly, before measures could stop its spread, leading to ‘multiple waves’ of cases over two years. In a ‘reasonable worst-case scenario’, health officials have suggested that social distancing measures would need to be reintroduced. However, they said the Government would not put the UK into a full Covid-style lockdown. The plans are set out in the first Health Security Risk Assessment, a report which also examines how outbreaks of respiratory infections, blood-borne viruses and weather-related hazards could play out. Ranking all of these, the UK Health Security Agency (UKHSA) said a new form of influenza poses one of the worst threats, with a potential impact of five, or ‘catastrophic’. And the likelihood of this happening is relatively high - between 5 per cent and 25 per cent. A fresh coronavirus outbreak, based on a new strain not linked to the previous pandemic, was also rated as catastrophic, and with the same likelihood. An outbreak of a new flu strain could, in the worst-case scenario, cost the economy £1.9trillion The document says that in the worst-case scenario, a new flu variant could infect half the population - about 33.5million people. Of these, the UKSA predicts 4 per cent would require hospital care, and a quarter of them - 1 per cent of the total infected - would need critical care. Economically, another pandemic could cost £1.9trillion, with 95million working days and 270million school days lost. There would be no lockdown, the UKHSA said, but the Government would recommend familiar measures including social distancing, hand hygiene and the use of masks to reduce transmission. The report added: ‘Isolation of cases whilst infectious and contact tracing close contacts of confirmed cases for quarantine may also help control the outbreak. ‘These measures would need strong public health communications to help tackle misinformation and where necessary, removal of barriers to help people follow guidance.’ The ‘reasonable worst-case scenarios’ imagined by the UKHSA are not a prediction of what is most likely to happen. Instead, the agency explains, they represent the ‘worst plausible manifestation of that particular risk’. Other risks in the report include dengue fever, which was classed as having a 1 to 5 per cent likelihood and a ‘minor’ impact - but this could increase with hotter weather. A tuberculosis outbreak and extreme heat were found to be the most likely, with a chance of at least 25 per cent, but they were not deemed to have a potentially serious impact. No comments have so far been submitted. Why not be the first to send us your thoughts, or debate this issue live on our message boards. By posting your comment you agree to our house rules. Do you want to automatically post your MailOnline comments to your Facebook Timeline? Your comment will be posted to MailOnline as usual. Do you want to automatically post your MailOnline comments to your Facebook Timeline? Your comment will be posted to MailOnline as usual We will automatically post your comment and a link to the news story to your Facebook timeline at the same time it is posted on MailOnline. To do this we will link your MailOnline account with your Facebook account. We’ll ask you to confirm this for your first post to Facebook. You can choose on each post whether you would like it to be posted to Facebook. Your details from Facebook will be used to provide you with tailored content, marketing and ads in line with our Privacy Policy.