Influenza

Background

• Transmission
  • Occurs in 6ft radius around infected pt who is sneezing and/or coughing
  • Viral shedding lasts ~5d (starts 24-48hr before onset of symptoms)
    • Longer duration of shedding occurs in children, elderly, pts w/ chronic illnesses
    • Shedding from asymptomatic individuals doesn't contribute significantly to transmission
• Convalescence
  • Most pts gradually improve over 2-5d, although may last for one week or more
  • Some pts have persistent weakness lasting several weeks (postinfluenza asthenia)

Risk Factors for Complications

1. <5yr (esp <2yr) OR >65yr
2. Chronic illnesses (asthma, cardiovascular (except HTN), renal, hepatic, SCD, DM)
3. Immunosuppression
4. Pregnant or within 2wk after delivery
5. Morbidly obese (BMI >40)
6. Residents of nursing homes / chronic care facilities

Clinical Features

• Constitutional
  • Fever
  • Headache
  • Myalgia
  • Malaise
• Respiratory
  • Non-productive cough
  • Sore throat
  • Rhinorrhea

Complications

1. Pneumonia
   1. Primary influenza PNA
      1. Most severe and least common type of PNA
      2. Rare in otherwise healthy adults
      3. Consider in pts w/ persistent and worsening symptoms (esp high fever, SOB, cyanosis)
      4. CXR shows b/l opacities w/ or w/o superimposed consolidation
   2. Secondary bacterial PNA

Source

UpToDate