Working as an infectious disease specialist at a tertiary care centre in Denmark over this past year has been busy and, at times, even chaotic. 

The pandemic has been fascinating from an academic point of view and has allowed us to become better acquainted with advanced concepts of epidemiology, virology, and vaccinology than we would otherwise have been. We have also been forced to make clinical decisions without the same degree of certainty that we are used to when managing patients admitted with acute medical conditions. Soon after making a treatment or management decision for a patient with covid-19, the basis for some of these decisions may have changed with a press release of the latest, groundbreaking, not-yet peer reviewed covid-19 study. 

Organisational changes in primary and secondary care have also been frequent in Denmark during the pandemic, as they have in other countries as well. Ominous early reports from China and Italy conferred an enormous pressure on healthcare authorities and hospital administrators to prepare for a surge of covid-19 patients, while ensuring appropriate care for other patients. Understandably, this is not an easy task. “Pandemic departments” were quickly established, often in temporary facilities without proper equipment and adequately trained staff, which are usually available at an emergency department. In addition, the clinical presentation of covid-19 has many faces, and setting up flawless visitation algorithms was impossible. To complicate matters further, shortages of personal protective equipment and test kits for SARS-CoV-2, mostly in the early stages of the of the pandemic, triggered a lot of uncertainty in managing acutely ill patients. Amid all this turbulence were the patients and healthcare workers providing care for them. 

Intrigued by early reports of lower hospitalisation rates for cardiovascular diseases during the spring of 2020, I discussed the collateral effects of the covid-19 pandemic with two good friends and fellow graduates from medical school. One of them, a cardiologist, concurred that he was seeing substantially fewer patients with myocardial infarction, while the other, an interventional neuroradiologist, was preparing for a surge of thromboembolic complications in covid-19 patients, as reported on social media and in medical case reports. These conversations prompted the idea to examine the potential collateral effects of covid-19 together with other colleagues and experts in epidemiology. 

Our study has now been published in The BMJ and shows substantially lower hospital admission rates across all major disease groups and higher associated 30-day mortality rates during national lockdowns in Denmark. Our study highlights the tremendous challenges and complexities of managing the covid-19 pandemic, both at the individual and organisational level. The disruption of the healthcare systems may have had immediate collateral effects on other acute medical conditions, but also more insidious effects on chronic diseases that may accumulate and manifest with time. For instance, we may find that many patients have experienced delayed diagnosis of cancer at a more advanced stage of the disease, or mismanagement of diabetes mellitus or cardiovascular diseases. Of note, our study is limited by a lack of clinical details on disease severity at presentation, and pre-existing comorbidities of hospitalised patients was not factored into our analyses.

We need to learn as much as we can from this pandemic in order prepare for the next. Our study is by no means conclusive, but may serve as a roadmap for future studies of collateral effects of covid-19. The need and imperative to improve treatment of covid-19 patients remains unquestionable. However, the toll of the pandemic may be unnecessarily high if we fail to deliver the same high level of care that we have spent decades, if not centuries, on developing for other serious medical conditions.

Jacob Bodilsen, medical doctor, Department of Infectious Diseases, Aalborg University Hospital, Aalborg, Denmark.

Competing interests: see research paper for full details.