Description 


  • Respiratory infection caused by influenza A or influenza B virus


ICD-9 codes 


  • 487.0 influenza with pneumonia

  • 487.1 influenza with other respiratory manifestations

  • 487.8 influenza with other manifestations

  • 488 influenza due to certain identified influenza viruses 


           – 488.0 influenza due to identified avian influenza virus 


           – 488.1 influenza due to identified novel H1N1 influenza virus 


  • V04.81 need for prophylactic vaccination and inoculation, influenza


Epidemiology 


  • Annual epidemics of seasonal influenza typically occur during late fall through early spring.


           – Typical incubation period is one to four days (mean two days). 


           – Children may be infectious for >10 days (from six days before the onset to 10 days after). 


           – Influenza can survive on dry inanimate surfaces for one to two days. 


Complications 


  • Illness may be more serious in children younger than age 2 years, especially age 6 months and younger, and in children with chronic immunosuppression or with respiratory or neurologic conditions.

  • Common complications include 


           – Pneumonia 


           – Otitis media


           – Tracheobronchitis


           – Acute sinusitis


           – Exacerbations of chronic pulmonary or cardiac disease


  • Febrile seizure 


History 


  • Pattern of illness may vary from mild respiratory illness to prostration with nonspecific signs and symptoms.

  • Initial presentation may be abrupt onset of fever (temperature 37.7-40˚C [100-104˚F]) and dry cough.

  • Symptoms that are often more common or more severe with influenza than with the common cold include


           – Fever


           – Myalgia


           – Arthralgia


           – Anorexia


           – Headache


           – Dry cough


           – Malaise


           – Fatigue


           – Weakness


  • Symptoms that are often less common with influenza (more common with common cold) include 


           – Nasal congestion


           – Sneezing


           – Sore throat


Physical examination


  • Fever is common.

  • Other findings may include 


           – Conjunctival injection


           – Nonexudative pharyngitis


           – Rhonchi or scattered rales