InfluenCEF study: Clinical phenotype and duration of headache attributed to influenza infection

Introduction Headache is a frequent symptom of infections. We aimed to characterize the clinical phenotype and duration of headache attributed to influenza infection. Methods Prospective cohort study done in 53 primary care centers between January and April 2023. Patients were included if they had a confirmed influenza diagnosis, were older than 15 years and had a new-onset headache. Patients’ demographics, prior medical history, headache phenotype and duration, associated symptoms and patients’ outcomes were assessed. The International Classification of Headache Disorders criteria for headache attributed to a systemic viral infection, migraine and tension-type headache were assessed. Results Of the 478 patients 75 fulfilled eligibility criteria. The mean age was 43, 56% were men, and 27% had a prior headache history. The headache phenotype was a bilateral headache (52%), with frontal topography (48%), pressing quality (61%), moderate intensity, rhinorrhea (79%), nasal congestion (76%), and photophobia (59%). All patients fulfilled headache attributed to acute systemic viral infection criteria, 43% fulfilled migraine criteria and 31% tension-type headache criteria. The median duration of the headache was four (Inter-quartile range: two-six) days. Conclusion The clinical phenotype of headache attributed to influenza infection was similar to other infections, with more pronounced cranial autonomic symptoms. The headache was an early symptom and was self-limited within a few days. Trial Registration: The study protocol is registered in ClinicalTrial.gov (NCT05704335)