1. Influenza is a serious disease caused by viruses that infect the respiratory tract.
2. An acute contagious viral infection.
(2008, Geary W.Skick. Protecting your business in a pandemic : plans, tools, and advice for maintaining business continuity. ISBN: 978-0-313-34602-6)
3. Influenza is a viral disease that causes high fever, sore through, cough, and muscle aches. It usually affects the respiratory system but sometimes affects other organs. It is spread by infectious droplets that are coughed or sneezed into the air. These droplets can land on the mucous membranes of the eyes or mouth or be inhaled into the lungs of another person. Infection can also occur from contact with surfaces contaminated with infectious droplets and respiratory secretions. Also see seasonal, avian, and pandemic influenza.
(2006, Pandemic Influenza Business Continuity Guide & Template for San Francisco Businesses. San Francisco Department of Public Health. Communicable Disease Control and Prevention Section.)