Influenza B Presentation in Elderly Patients
An Altered Presentation — An Altered Approach to Diagnosis

Subir Vij, M.D.

 

Objective: To describe the clinical symptoms associated with influenza B infection in frail institutionalized elderly people.

Methods: Prospective active surveillance was used to identify symptomatic residents and to follow their course of influenza for subject enrolled in a NIH-sponsored study. (377 Residents enrolled in 92-93).Setting: A 685-bed long-term care facility for veterans and their spouses.

Patients: The subgroup of 66 study subjects from whom influenza B was cultured and complete prospective clinical data was available.

Measurements: Follow up throat and nasopharyngeal virus cultures; analysis of sera for anti-influenza antibodies recording of respiratory and constitutional symptoms twice weekly by study staff. Also, charts were reviewed, and all relevant comments by regular nursing staff were recorded. All data reported is prospective and is presented as descriptive statistics

Results: Sixty-six residents in whom clinical respiratory illness was prospectively identified and influenza B confirmed by culture were followed. Between November 18, 1992, and April 16, 1993 38% of the patients had low-grade fever (_99°F) at presentation, one third had no fever at any time, and 5% had low-grade fever for up to 9 days. Clinical presentation included lower respiratory tract symptoms in more than 80% of subjects with influenza B, throat symptoms in approximately a third, nasal symptoms in 60%, and constitutional symptoms in over half.

Conclusion: Over 60% of the vaccinated elderly may not present with fever at the onset of influenza B. Since anti-influenza treatment must begin within 48 hours of disease onset, it is crucial that physicians do not rely on fever alone to make the diagnosis of influenza.