Emergency Central is a collection of disease, drug, and test information including 5-Minute Emergency Medicine Consult, Davis’s Drug, McGraw-Hill Medical’s Diagnosaurus®, Pocket Guide to Diagnostic Tests, and MEDLINE Journals created for emergency medicine professionals. Explore these free sample topics:
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- Acute, usually self-limited, viral infection
- Transmission: By dispersion in small-particle aerosols created by sneezing, coughing, and talking
- Virus is deposited on respiratory tract epithelium and absorbed.
- Incubation period: 1–4 days (avg. 2)
- Mean duration in adults: 4 days
- Seasonal outbreaks most common in February.
- 2009 novel H1N1 pandemic peaked in fall and early winter of that year. Children and pregnant women had particularly high complication rates.
- Primary influenza viral pneumonia
- Secondary bacterial pneumonia
- Exacerbations of COPD
- Otitis and sinusitis in children
- Reactive airway disease
- Rare complications: Myositis, myocarditis, pericarditis, Guillain–Barré syndrome, and aseptic meningitis
- ARDS and multisystem organ failure
- Key features:
- Seasonal epidemics are spread by high attack rates in immunologically naive children.
- Intermittent unpredictable pandemics
- Mortality results largely from pulmonary complications.
- Children exhibit more lower respiratory involvement (croup, bronchitis, bronchiolitis, pneumonitis) and higher temperatures than adults.
- Children were particularly susceptible to complications of novel H1N1 influenza virus.
- Myalgias in the calf muscle
- Febrile convulsions occur in ∼10% of children <5 yr of age with influenza infection.
- Reye syndrome:
- Influenza may be a predisposing factor.
- Rare and severe complication associated with salicylate use (children taking aspirin chronically are recommended to get vaccinated)
- Acute liver and brain injury
- Caused usually by 1 of 2 influenza types, A or B, the latter usually less severe.
- Influenza A subtypes are classified by hemagglutinin antigens H1, H2, or H3 and less importantly by the neuraminidase subtype.
- Vaccine targets the subtype antigen, which is also the target of natural immunity.
- Annual epidemics are seasonal:
- Caused by antigenic drift—new variants from minor changes in surface protein
- Duration of epidemic <6 wk
- Caused by antigenic shift—major changes in virus structure
- Waterfowl reservoir of influenza virus
- Avian flu has proven difficult to transmit to humans and between humans, but infection is often very severe.
- The 3 most common strains in 2012 (most vaccinations cover) were influenza B viruses, influenza A (H1N1), and influenza A (H3N2)