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. 
Department of Pulmonary, Allergy and Critical Care
CR declares that she has no competing interests.
Medical Director of Infection Control
Department of Medicine
SUNY Upstate Medical University
WJ declares that he has no competing interests.
Associate Professor of Clinical Medicine and Environmental Health Sciences
Columbia University College of Physicians and Surgeons
RLM declares that she has no competing interests.
SUNY Buffalo School of Medicine
Division Allergy and Immunology
MS declares that he has no competing interests.
Department of General Practice and Primary Health Care
ADS declares that she has no competing interests.
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