What evidence supports the long-term health risks associated with common respiratory infections like influenza and RSV?

Evidence points to several ways that common respiratory infections like influenza and RSV can cause long‑term health problems. The risks range from heart attacks and strokes after flu to lasting breathing trouble after RSV, and researchers are uncovering general pathways that turn acute infections into chronic illnesses. Here’s what the supplied studies show.

Cardiovascular dangers following influenza

A bout of flu can sharply raise the chance of serious heart and blood‑vessel events in the weeks afterward, and those events often have long‑term consequences.

• A population‑based study found the risk of atherothrombotic events more than doubled during the 14 days after a flu infection, even in milder cases and in people with fewer existing risk factors [5].
• According to the American Heart Association, people are 4 times more likely to have a heart attack and 5 times more likely to have a stroke in the month after a lab‑confirmed flu infection [3].
• Broader research confirms that influenza infection is tied to an elevated risk of acute cardiovascular events [1][2], and that these complications pose a significant threat to vulnerable patients, such as those with congenital heart disease [4].

Neurological effects that can persist after influenza

Flu doesn’t just hit the lungs; it can affect the brain, sometimes leaving lasting neurological problems.

• Influenza A virus infection has been shown to cause cognitive impairment [10].
• Among survivors of severe flu‑associated brain involvement, many are left with long‑term neurological problems [11].
• More generally, influenza is recognised for triggering neurological complications like encephalopathy and seizures [12].

Respiratory aftermath of RSV – especially in children, but also in adults

Respiratory syncytial virus (RSV) is strongly linked to long‑term breathing troubles, particularly when the infection happens early in life.

• There is growing evidence that RSV lower respiratory tract infection (LRTI) in early childhood is associated with long‑term wheezing, asthma, and impaired lung function [6].
• Early‑life RSV LRTI has also been connected to later respiratory sequelae such as recurrent wheezing, recurrent LRTI, and asthma [7].
• These effects aren’t limited to kids: adults hospitalised with RSV can experience lasting symptoms like breathlessness and reduced daily functioning [8]. Even after the infection clears, a serious RSV illness can cause health problems for a long time [9].

How RSV stacks up against flu in long‑term harm

When comparing the two infections, evidence suggests RSV is at least as dangerous as influenza over the long haul – and sometimes worse.

• RSV infections have shown comparable or greater health threats than influenza, not only during the hospital stay but also in long‑term outcomes [14].
• Over the long term, RSV can be deadlier than flu [13], and among older adults, mortality from both infections is similarly high [15].
• The disease caused by RSV in older adults may be more severe than flu [16], with higher rates of complications like consolidative pneumonia, more hospitalisations, more ICU admissions, and longer lengths of stay [17].

The bigger picture: infections can kick off chronic illness

A growing body of research shows that acute infections – including respiratory ones – can set the stage for persistent ill health, a concept that helps explain some of the long‑term risks of influenza and RSV.

• Chronic illnesses such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have long been linked to infectious triggers [18], and post‑infectious syndromes overlap with chronic viral infections; an acute infection can result in documented, ongoing clinical morbidity [19].
• ME/CFS and long COVID share similar symptoms and underlying biology, partly involving the body’s “sickness behaviour” response [20].
• Certain acute infections have a known ability to cause unexplained chronic disability in a minority of patients [21]. These post‑acute infection syndromes (PAISs) represent a substantial healthcare burden [22], and infection can lead to lasting symptoms and problems across many body systems [23].

Together, these findings show that influenza and RSV aren’t just short‑term illnesses – they can leave a footprint that lasts months or years, affecting the heart, lungs, brain, and overall daily function. The evidence also underscores that scientists are actively piecing together the pathways behind these lingering effects.