Influenza Initial Assessment

Clinical Presentation

Influenza-like illness is an acute respiratory infection manifested as a temperature of ≥37.8°C and cough with an onset within the last 10 days. 

The clinical spectrum of influenza ranges from asymptomatic infection to primary viral pneumonia that may progress to death. Patients presenting with influenza-like illness might be infected with different types of influenza virus (eg avian influenza A[H5N1], A[H7N9]), as well as other respiratory pathogens. A high index of suspicion is needed to recognize influenza in hospitalized patients. 

Clinical Presentation of Seasonal Influenza  

The typical signs and symptoms of seasonal influenza include an abrupt onset of fever, severe myalgia and/or arthralgia, severe dry cough, pleuritic chest pain, loss of appetite, abdominal pain, diarrhea, headache, malaise, fatigue, sore throat, and rhinitis.  

Physical examination of patients with seasonal influenza may present with flushing, pain on eye movement, nonexudative pharyngitis, and scattered rales or rhonchi. Elderly patients may have hot, dry, or diaphoretic skin. 

Clinical Presentation of Zoonotic Influenza   

Avian Influenza A(H5N1) Should Be Suspected in the Following:

• Documented temperature of >38°C and
• ≥1 of the following: Cough, sore throat, and/or shortness of breath and
• Contact history:
  • History of contact with sick or dead poultry, family members with suspected or confirmed H5N1 infection, healthcare workers of suspected or confirmed H5N1 patients, laboratory workers handling specimens or viral cultures of H5N1 viruses
  • History of living in an endemic area or an environment with sick or dead poultry
  • If the patient only has a history of travel to endemic areas, a risk assessment will need to be individualized

Avian Influenza A (H7N9)  

Avian influenza A (H7N9) is a subtype of influenza virus first reported in March 2013 in China. Transmission is by direct contact with infected poultry or exposure to the environment of infected poultry. No human-to-human transmission has been recorded yet. Signs and symptoms are the same as seasonal influenza, but it is most often accompanied by a history of severe pneumonia.

Other Reported Presentations of Avian Influenza in Humans  

Other presentations include typical influenza-like symptoms (abrupt onset with headache, high-grade fever, sore throat, chills, dry cough, malaise, myalgia, anorexia), dyspnea or bloody sputum, chest pain, bleeding from the nose and gums, gastrointestinal upset (vomiting, diarrhea, abdominal pain), neurological symptoms (eg stupor, convulsions), conjunctivitis, pneumonia or pneumonitis, and acute respiratory distress.