Over the past couple of months, deaths in England and Wales have been higher than would be expected for a typical summer. In July and August, there were several weeks with deaths 10% to 13% above the five-year average, meaning that in England about 900 extra people a week were dying compared with the past few years. The leading causes of death are within the typical range (the five-year average): heart and lung diseases, cancers, dementia and Alzheimer’s disease. Covid-19 deaths could account for half of the excess mortality, but the other half is puzzling, as there’s no one clear reason that jumps out. It’s likely to be a mix of factors: Covid is making us sicker and more vulnerable to other diseases (research suggests it may contribute to delayed heart attacks, strokes, and dementia); an ageing population; an extremely hot summer; and an overloaded health service meaning that people are dying from lack of timely medical care. This winter, the cost of living crisis and concerns about fuel poverty will add to these contributory factors, given the links between deprivation and ill health. So we may see these excess death numbers continue. The excess mortality puzzle has been weaponised by some to argue that this is a delayed consequence of lockdown. In essence, this is to say that mandatory restrictions on mixing and stay-at-home legal orders, as well as turning the NHS into a Covid health service during the first and second waves of infection, prevented people from being diagnosed or treated for other conditions such as cancer, heart disease, or even depression – and that those long-hidden conditions are now killing people. Of course, some medical care suffered during the pandemic, and delayed diagnosis leads to poor health outcomes. But to say that not having restrictions would have solved this problem is naive. Restrictions ultimately limited the number of people hospitalised for Covid-19 at any one time, so that the health services could cope with these numbers. Healthcare is finite: the best way to preserve resources for non-Covid conditions was to keep Covid infections as low as possible. Given the UK government’s delay in responding to Covid-19 and implementing measures to suppress it in the first and second waves, the NHS struggled to provide high-quality care to all those who arrived in hospital. Countries that managed to avoid large numbers of Covid-19 patients in the pre-vaccine era through smart suppression based on testing and isolation, such as New Zealand and South Korea, managed to keep their health services running for a wider range of conditions. The UK initially took the path of late, and thus longer, lockdowns without a clear exit strategy, with England in particular struggling to implement test/trace/isolate and learn from the mistakes of the first wave. The excess mortality data points to three key issues. The first is that the NHS is overloaded, quality of care is suffering, staff are burnt-out and leaving their positions, and this is leading to medical care being delayed for acute conditions (heart attacks and strokes) but also chronic ones, where every week and month matters, such as cancer treatment and surgeries. Too many ambulances are unable to offload. Unfortunately, certain politicians have turned to blaming NHS staff for being lazy and only doing virtual appointments, or being off work with illness. What’s clear is that we need real investment in the NHS, in its people, facilities and operations, so that it is an attractive place to work that can provide the volume and quality of care needed. Second, Office for National Statistics data has shown that mortality jumped on days with extreme heat. We know extreme weather events are becoming more common, and that higher temperatures can lead to strokes, heart attacks and blood clotting in elderly and vulnerable groups. This problem is not going away as climate experts warn that what we see as unusually hot temperatures will become the norm over the next 50 years. But most importantly: Covid-19 is still circulating and killing people, especially those in elderly groups and those who are unvaccinated. While it has dropped from being the leading cause of death, it is still one of the top 10 causes of death in the population, and even with a much-reduced fatality rate due to vaccination and prior infection, it is contributing to that 10-13% jump in summer excess mortality. In fact, as these figures show from the ONS, many other major causes of death are slightly below the five-year average. The good news is that the fatality rate for Covid-19 – the chance of death when infected – is now below seasonal flu for the vast majority of people. This is because of scientific developments and the efforts by governments to delay the spread of Covid-19 until vaccinations could be rolled out. The bad news is that it’s still a cause of disability and death, alongside heart disease, cancer, dementia and other challenges. Instead of illogical arguments about whether lockdown was responsible for excess mortality – entirely without evidence – it’s worth taking a closer look at the data, which suggests that, in fact, it’s a mix of the new burden of Covid-19 and an overloaded health service, with days of extreme heat thrown in. As always, a clearer picture will emerge with more research and analysis over time. For now, we should be focusing on how to develop better treatments and vaccines to bring the mortality rate of Covid-19 down further, investing in the NHS to ensure quality and timely care, and looking at how to better cope with extreme weather events. Global events such as the Covid-19 pandemic and climate change are making us all sicker. If we could just acknowledge their impact across political lines, we could work together on solutions. Devi Sridhar is chair of global public health at the University of Edinburgh