A fresh NHS crisis is looming. Diseases that have gone undiagnosed and treatments that have been delayed because of lockdown have already cost lives and will cause thousands more avoidable non-Covid deaths in the months and years to come. As our strategy to deal with the epidemic evolves, this “invisible” crisis must be given the attention it deserves.

When the pandemic first hit, the UK the government’s understandable priority was to prevent hospitals being overwhelmed. The message – “Stay Home, Protect the NHS, Save Lives” – was heard loud and clear. Millions of non-urgent operations, screenings and appointments were cancelled by hospitals and patients themselves. Emergency admissions plummeted.

The result is that thousands of patients who have needed medical help have not sought it and have gone untreated.

Medical experts have long been warning of the impact of shutting down routine NHS services. The full extent of the healthcare deficit has now been revealed after research by the healthcare analysts Dr Foster charted the dramatic decline in hospital admissions during April and May.

Admissions for prostate cancer – the most common form of cancer in men – fell by nearly two thirds (64%) with 4,640 admissions compared to a five-year average of 12,589. For breast cancer, the slump was 30%, for bowel cancer  39%, and for “non-specific chest pains” – a red flag for a heart attack– the fall in admissions was 41%.

The Care Quality Commission has said that 27 million fewer GP appointments took place between March and August 2020 compared with the same period last year, leading to fewer referrals to hospitals for important checks.

Cancer Research UK has calculated that between April and July, the number of patients starting cancer treatment was 26% lower than last year, meaning that a total of 31,000 patients have gone untreated.

NHS figures show that organ transplants also fell by two thirds in April and May and that the number of cancelled operations runs into the millions.

While it is still difficult to accurately gauge, the impact of reduced admissions is becoming clearer.

The Office for National Statistics published data this week showing that 25,472 more people died at home in England and Wales between 28 December 2019 and 11 September 2020 than the five-year average. Only 2,358 of those deaths involved Covid.

The figure is shocking but it shouldn’t be taken at face value. Non-Covid deaths in hospital settings declined over the same period and it’s likely that many excess home deaths would have occurred in hospital under normal circumstances, although it is unclear how many.

A better way to assess the impact of lockdown is to look at “excess deaths”, the difference between the number of deaths this year and the average number over the previous five years. There have been 57,300 excess deaths from all causes in England and Wales so far this year. Of these, around 50,600 have been Covid deaths, where the coroner has listed coronavirus as a contributory factor in the death.

The gap between these two figures of around 6,700 is a reasonable guess at the non-Covid excess death toll so far.

Many of the deaths are yet to come. Cancer, in particular, is being referred to as a ticking time bomb. One of the more conservative estimates from a study in The Lancet Oncology journal suggests that between 3,291 and 3,621 lives could be lost to lung, breast, colorectal and oesophageal cancer over the next five years as a result of delays to treatment during lockdown.

Research by Health Data Research UK, the national institute for health data science, has warned that the overwhelming focus on Covid-19 is likely to cause between 7,000 and 18,000 excess cancer deaths within just one year.

There are fears that those who need medical help this winter will again decide to stay at home for fear of clogging up the system or caching the virus. NHS chiefs have launched a new campaign – “Help Us Help You” – encouraging patients to attend hospital if they need to, by assuring them that they won’t be a burden on the system.

The message could struggle to gain traction alongside the government’s consistently alarming Covid rhetoric. In the early days of the pandemic, prioritising the virus was entirely understandable. And it is still true that unless numbers of Covid patients are kept under control, the NHS could be overwhelmed.

But because lockdown is such an unprecedented juggernaut of a policy, unintended consequences are inevitable. Now the far-reaching effects have become clear and those proposing further lockdown measures must start carefully counting the wider health costs in with the Covid calculus.

The relentless focus on the Covid death toll above all else is warping our view of the relative risks from the virus and the policies we are using to combat it. Until both Covid and non-Covid deaths are given equal weight in the government’s decision-making, this new, non-Covid health crisis will remain invisible, though no less real.