This study investigate the prevalence of elevated biomarkers of cardiac injury in patients with suspected influenza infection and the prognostic implication on the composite endpoint of death of any cause, hospitalization due to myocardial infarction, unstable angina, heart failure and stroke.

The relationship between influenza and cardiovascular events was described in an early study of influenza epidemics from 1915 to 1929 including the 1918-1920 pandemic. Retrospective studies have shown increased risk for acute myocardial infarction (AMI) during the first week following an infection with influenza.

Biochemical markers of cardiac injury such as high sensitive cardiac troponins may be increased during infection with influenza. Increased levels of cardiac troponins are associated with adverse outcome in many different populations.

Inclusion Criteria:

• Adult patients (>18 years) presenting with influenza-like illness.
• Written informed consent.

Exclusion Criteria:

• Inability to provide informed consent.
• Age <18 years.
• Symptoms indicating an acute coronary syndrome, acute heart failure, rapid atrial fibrillation or acute stroke.

The clinical study will be conducted in Region Örebro County. Recruitment will start October 1st 2017 and is expected to continue for two influenza seasons until April 30, 2019. Individuals for inclusion are recruited among adult patients > 18 years presenting with influenza-like illness at the emergency unit and who, due to strong clinical suspicion of ongoing influenza infection, are tested.