The consequences of infectious diseases extend beyond the acute phase of the illness: Influenza, COVID, pneumonia, and other such illnesses are not only acutely dangerous but also can cast a long shadow over one’s health — from metabolic diseases such as diabetes to an increased risk for heart attacks, emphasized Leif Erik Sander, MD, Medical Director, Department of Infectious Diseases and Critical Care Medicine at Charité — Universitätsmedizin Berlin, Berlin, Germany and member of the Executive Board of the German Society of Infectious Diseases, at the press conference held on the occasion of the 17th Congress for Infectious Diseases and Tropical Medicine.

Nevertheless, infections are often underestimated, particularly with regard to their long-term consequences; we now know from many large studies that in the weeks following an acute infection, the risk for heart attacks and strokes is significantly increased — by a factor of 3-7 — which is substantial, said Sander.

A study from last year shows that the risk of suffering a stroke in the 4 weeks following the onset of the flu is five times higher than in people without influenza. During the same period, the risk of having a heart attack is four times higher. Within 4 weeks of a SARS-CoV-2 infection, the risk for a heart attack is 3.1 times higher and the risk for a stroke is 2.9 times higher.

Herpes, Dementia, Vaccination Link

Sander reported estimates suggesting that 5%-10% of all cardiovascular events are at least partly triggered by prior infections. The increased risks for cardiovascular events can persist for months.

Certain herpes simplex infections are associated with an increased risk for dementia. Conversely, vaccination against herpes zoster (shingles) is associated with a reduced risk for dementia; a risk reduction of up to 20% was observed in women.

Flu Tied to Diabetes, Chronic Kidney Disease (CKD)

A cohort study from England published in May 2026 shows that following hospitalization for influenza, the risk of developing diabetes for the first time increases significantly.

Sophie Middleton of the NIHR Nottingham Biomedical Research Centre, Nottingham, England, and colleagues included 13,710 adults who were hospitalized for influenza between July 1, 2004, and March 1, 2021, and who had no preexisting diabetes. The following groups served as comparators:

• a randomly selected group matched for age, sex, and general practice, drawn from the Clinical Practice Research Datalink database 
• an unmatched group of hospitalized patients with sepsis 

The highest risk of developing diabetes among hospitalized patients with influenza occurred within 90 days of discharge (adjusted hazard ratio, 2.71; 95% CI, 1.94-3.77; P < .001) compared with matched control individuals. Risk factors for diabetes following hospitalization for influenza included male gender, a preexisting risk for diabetes, obesity, and admission to the ICU during the acute illness.

Another intermediate and late consequence of infections is an increased risk for CKD, as demonstrated by collaborative projects between Charité and the Israeli CLALIT Health Services, Sander reported. He speaks of a specific association with this chronic organ damage. It is also known that people who already have damaged kidneys from the outset often suffer more severe infections. This is a mutually reinforcing cycle.

Rethinking Infectious Diseases

“We need to rethink infectious diseases. They are not just a short-term health threat with a significant economic burden and major consequences for acute healthcare, but a health determinant that affects the entire lifespan. And they are also an important — and likely underestimated — driver of chronic diseases,” Sander emphasized.

A common denominator in the mid- to long-term consequences of infectious diseases is inflammatory activity that does not return to normal levels or the baseline inflammation level after the acute inflammatory phase of the infection, explained Maria Vehreschild, head of the Infectious Diseases Division at Frankfurt University Hospital, Frankfurt, Germany. This upregulated inflammation plays a role in a wide range of diseases — including vascular inflammation, cardiovascular and nephrologic diseases, and disorders of the central nervous system.

Inflammation can also lead to changes in organ tissue. “I believe we have not yet fully understood which mid- and long-term consequences this increased inflammatory activity might affect. We’re just beginning to understand that,” said Vehreschild.

Vaccines Reduce Long-Term Complications

The mid- and long-term consequences of infections bring the value of vaccinations even more into focus. “Vaccinations are very effective, relatively easily accessible, and cost-effective preventive measures that deserve more attention,” emphasized Sander.

Sander emphasized that the evidence base is particularly strong for vaccinations against influenza and herpes zoster. For other vaccines, such as those against SARS-CoV-2, initial cohort studies and analyses are now available. The fact that vaccinations can protect against cardiovascular events has been the subject of increased discussion during the COVID pandemic. Controlled studies on the influenza vaccine have already shown that the vaccine also provides cardiovascular protection, but these studies received little attention at the time.

The influenza vaccine contributes significantly to the prevention of cardiovascular events. According to a recent meta-analysis, major adverse cardiovascular events were reduced by 45%.

The results of the Influenza Vaccination After Myocardial Infarction study also confirmed the importance of the influenza vaccine in secondary prevention following a myocardial infarction.

Among patients vaccinated against influenza during treatment for acute myocardial infarction, the rate of major adverse events at 1 year — including death, recurrent myocardial infarction, and stent thrombosis — was lower than that in the placebo group (5.3% vs 7.2%). All-cause mortality and cardiovascular mortality were also reduced among vaccinated patients, at 2.9% vs 4.9% and 2.7% vs 4.5%, respectively.

Infections Carry Major Economic Costs

Sander pointed out that even the acute disease burden has significant impacts. When respiratory infections are considered from an economic perspective, the costs of annual influenza infections in the EU alone are estimated at €10-€14 million.

Added to this are the costs resulting from absenteeism and lost productivity, which exceed €100 billion/y in the EU alone. “Prevention through vaccinations would be a major lever here, with direct economic benefits,” Sander pointed out.

Sander expressed surprise that, of all things, the Commission had singled out the 10% increase in vaccination costs as a factor in stabilizing statutory health insurance funds. “In my view, our problem isn’t that we spend €3 billion euros a year on vaccinations; our problem is rather that we don’t spend €30 billion euros a year on vaccinations. Vaccinations are the most effective lever for prevention,” Sander emphasized.

What is needed, he said, is an effective infectious disease medicine program as a central component of modern healthcare. In his view, investments in prevention, vaccination programs, research, and clinical infectious disease care are crucial. We need not only investments in combating infectious diseases but also investments in health and in the resilience of our healthcare system.

This story was translated from Medscape’s German edition.