Background
Microbiology
- Enveloped, single-stranded, negative-sense RNA virus in the Orthomyxoviridae family
- Four genera corresponding to influenza A through D
- Typed by hemagglutinin (HA) and neuraminidase (NA) proteins
- Antigenic drift refers to small mutations
- Antigenic shift refers to large changes from reassortment
Epidemiology
- Worldwide
- Seasonal in temperate climates, lasting from fall through spring and peaking in late winter
- Antigenic drift usually results in local outbreaks, while antigenic shift can result in epidemic or pandemics
Clinical Manifestations
- Fever and respiratory symptoms, especially with myalgias
Management
- Neuraminidase inhibitors started within 48 hours of symptom onset are associated with a shorter duration of illness
- Monitor for secondary bacterial pneumonia
Prevention
- Annual influenza vaccination is recommended for everyone 6 months of age and older
- Chemoprophylaxis with oseltamivir may be indicated as post-exposure prophylaxis or during local outbreaks for all people at risk
