Influenza-like Illness in Elderly Persons

Influenza-like illness (ILI) is suspected when an individual exhibits a cough and fever (>100° F) or chills.

Clinical manifestations

Influenza-like illness (ILI) in elderly persons may be atypical. Such patients generally present with a new onset of cough, sore throat, nasal congestion or rhinorrhea, or a temperature 100° F or greater; however, fever may be absent. Elderly patients also may have atypical complaints such as anorexia, mental status changes, and unexplained fever as the only presenting symptoms.

Worsening respiratory status in patients with underlying chronic obstructive lung disease and congestive heart failure may be an unrecognized complication. Other complications include primary viral pneumonia and bacterial superinfection leading to tracheobronchitis or pneumonia.

Transmission

Influenza transmission occurs predominantly by large respiratory droplets (particles >5 µ in diameter) that are expelled from the respiratory tract during coughing or sneezing. Particles usually do not remain suspended in the air, and close contact (< 3 feet) usually is required for transmission. Transmission also occurs through direct contact with respiratory droplets or secretions, followed by touching the nose or mouth.

Infectiousness begins 24 hours prior to onset of illness. Adults are usually contagious until five days after onset of symptoms; however, immunocompromised individuals may shed virus for seven days or more after onset of symptoms.

The incubation period for influenza is one to four days, usually two days.