The link between influenza and serious heart conditions just grew stronger.

A CDC study looking at more than 80,000 adult patients hospitalized with flu over eight seasons found that sudden, serious heart complications were common, occurring in 12% of patients, or 1 in 8. “Previous to our study, there had been suggestions between the link, but our study shows just how common it is,” said lead author Eric Chow, an infectious diseases fellow at University of Washington School of Medicine.

The study, published Aug. 25 in the Annals of Internal Medicine, underscores the importance of getting a flu shot early. “There are few respiratory viruses we have a vaccine for,” he said. “Our team motto is 'Get a flu shot.'”  Chow previously worked as an epidemic intelligence service officer, or “disease detective,” for influenza at the Centers for Disease Control and Prevention. 

The study found that 5% of patients hospitalized with the flu had a cardiac complication despite having no documented underlying conditions. In the last month, there have been cases of otherwise healthy athletes showing signs of heart complications after recovering from COVID-19. For example, 27-year-old Florida State basketball player Michael Ojo, who recovered from COVID-19, died of an apparent heart attack at a practice.

Chow said he is not surprised this is happening to healthy people who have been infected with SARS-CoV-2, the virus that causes COVID-19.  The virus can cause damage to the lungs and other organs, including the heart. Inflammation makes hearts vulnerable to potentially fatal arrhythmias during vigorous exercise.

In this study of adults hospitalized with flu, 12% had acute heart complications. Of these, 30% were admitted to the ICU and 7% died while in the hospital. The CDC recommends that everyone 6 months and older get a flu vaccine every flu season. According to the CDC, flu vaccination is always considered important for people at high risk of developing serious flu complications, including people with heart disease. Flu shots are approved for people with heart disease, but people with heart disease should not receive the live attenuated influenza vaccine (LAIV, also known as the nasal spray flu vaccine). However, any intramuscular flu shot, such as any inactivated or recombinant influenza vaccine, would be appropriate.