Flu infections reach beyond the lungs, and the heart is part of the picture

Flu has a reputation as a lung bug. It turns out the story is bigger than that, and knowing it gives you a clearer view of what a flu season can involve. A new review of research on infections like influenza found that a large share of serious flu illness shows up outside the lungs, and that heart problems stand out most for older adults.

That is useful to know, not scary. It means doctors and public health teams are now counting the full picture, so prevention plans can be built around it.

How the study worked

Researchers pulled together 238 earlier studies from 52 countries or regions. They looked at how much severe flu illness happens beyond the respiratory system, and at the methods scientists use to estimate it. The review was published November 3, 2026 in Lancet Healthy Longevity. Most of the evidence came from wealthier countries, so the picture is less complete for other parts of the world.

What they found

The main result is that problems outside the respiratory system make up a substantial part of the total burden of flu. Think of the heart, the blood vessels and other body systems that a flu infection can stir up, not only the lungs and airways.

Age made a big difference. The share of this non-lung burden was greatest in adults 65 and older. Among that group, heart and blood vessel events were especially notable. They were tied to more than 50 deaths and 60 hospitalizations, counted as a rate across the older population.

Here is a plain way to read that. The studies point to a real number of heart-related deaths and hospital stays connected to flu. Those are events that a simple count of “flu cases in the lungs” would have missed.

The numbers were not identical from study to study. They varied with the method researchers used, the cause they counted and the years they looked at. That is why the authors call for shared, standard ways of measuring this, so results can be compared across places and flu seasons.

Why does the heart come into it?

Your body works as one connected system. When an infection sets off a strong response, the effects can spread beyond the place the germ first lands. This review did not set out to explain the exact reasons. Its job was to count how often these non-lung problems show up in the research, and the answer was: often enough that they should be part of the conversation.

What this means for planning

The authors say flu burden assessments and prevention strategies should look past respiratory symptoms, particularly for older people. In practice, that points toward planning that treats flu as a whole-body concern. It also points toward collecting better data in more parts of the world.

What you can do today

Take two minutes to look up flu prevention options for this season. Stop by your pharmacy or call it, and ask what is available to you and when you can get it. If you are 65 or older, or you help care for someone who is, make it a family errand and put it on the calendar.