Introduction: When influenza (flu) season arrives, it is easy for emergency department clinicians to anchor on the diagnosis of flu, sending patients on their way with or without anti-influenza medication. It is important not to miss the outlier – the patient who seems to have typical symptoms of influenza but with certain subtleties that should make one consider expanding the differential diagnosis.

Case Report: We describe an 11-year-old previously healthy male who presented with eight days of fever, myalgias, cough, congestion, and headache in the context of positive influenza exposure. The length and severity of his symptoms prompted laboratory and imaging investigation. He was positive for influenza type B with elevated inflammatory markers but otherwise normal laboratory workup and normal chest radiograph. He complained of a headache and was given fluids and antipyretics, and was admitted for overnight observation. He specifically did not have any forehead swelling. The next day during his inpatient stay he developed right frontal forehead edema and appeared ill. He was taken for a sinus computed tomography, which showed changes consistent with frontal bone osteomyelitis. Even after drainage by neurosurgery and otolaryngology, the patient subsequently developed repeat abscesses and ultimately a superior sagittal sinus thrombosis.

Conclusion: Other sources of infection should be considered in patients who have flu-like symptoms that last longer than expected, present with focality, or appear ill.