• 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


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

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

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           – 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. 


  • 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 


  • 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