People are six times more likely to have an acute myocardial infarction (AMI) in the week after they test positive for influenza, according to a Dutch study.

Researchers analysed 26,221 cases of laboratory confirmed influenza. Of these, 401 had 419 AMIs within a year of their flu diagnosis: 6.0 per cent in the first seven days after flu diagnosis, 51.8 per cent in the year before and 42.2 per cent during the year after flu diagnosis, excluding the first seven days. 

Overall, people were 6.16 times more likely to have an AMI in the seven days following a flu diagnosis than in the year before or after. 

Inflammation, part of the immune response against influenza, can weaken fatty plaques in the arteries. The influenza virus increases coagulation. If a plaque ruptures, a blood clot can form causing an AMI.

“Our results endorse strategies to prevent influenza infection, including vaccination,” says Dr Annemarijn de Boer from the Julius Centre for Life Sciences and Primary Care, University Medical Centre, Utrecht.

“They also advocate for a raised awareness among physicians and hospitalised flu patients for symptoms of heart attacks. While it isn’t clear from our results if those with less severe flu are also at risk, it is prudent for them to be aware of the link.”

The study was presented at the recent European Congress of Clinical Microbiology and Infectious Diseases in Copenhagen.