Influenza infection is characterized by upper and lower respiratory tract symptoms of rhinorrhea, cough, fever, chills, headache, and myalgia.
Typically presents in winter season.
Can occur in local community outbreaks, epidemics, and, rarely, pandemics.
Vaccination for prevention is available.
Acute respiratory tract infection typically caused by influenza A or B virus. The virus is transmitted by inhalation of infected respiratory secretions that have been aerosolized through coughing, sneezing, or talking.
History and exam
Key diagnostic factors
- winter season
- current influenza outbreak
- fever with cough
Other diagnostic factors
- sore throat
- cervical lymphadenopathy
- age ≥65 years
- age 6-59 months
- chronic cardiovascular or respiratory conditions
- chronic kidney disease (CKD)
- caregivers and household contacts of high-risk groups
- healthcare workers
1st investigations to order
- clinical diagnosis
Investigations to consider
- viral culture
- direct immunofluorescent antibody staining
- reverse transcriptase-polymerase chain reaction
- enzyme immunoassay (EIA)
- rapid diagnostic tests
- chest x-ray
exposure to infected individual(s) in at-risk population
- Coronavirus disease 2019 (COVID-19)
- Bacterial pneumonia
- Respiratory syncytial virus (RSV) infection
- Recommended adult immunization schedule for ages 19 years or older, United States, 2022
- Recommended child and adolescent immunization schedule for ages 18 years or younger, United States, 2022
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