On April 17, 2009, two patients in the United States were found with Swine-Origin Influenza A (H1N1) virus. This virus was spread to Mexico, Canada, and many other countries. From April 15 through May 5, a total of 642 confirmed cases of H1N1 infection were identified in 41 states. The ages of the patients were from 3 months to 81 years, and 60% of the patients were 18 or younger. Most of these patients recently came from either Mexico or even from school outbreaks. The most common symptoms were fever, cough, and a sore throat. The H1N1 was determined to have a unique genome composition that had not been identified previously (Padilla et al., 2009).
Consford, Kail and Patel, Drew, "H1N1 Influenza Virus" (2015). Infectious Diseases Project 2015. 3.