The document discusses Spanish flu and influenza A. Spanish flu first appeared in 1918 during World War I and was called Spanish flu because Spain was not engaged in the war and freely reported on the disease. It infected one third of the global population and killed around 50-100 million people, making it the deadliest pandemic in history. Influenza A is a type of flu that naturally infects birds but can also infect humans and pigs. The 2009 H1N1 pandemic was an influenza A virus that was declared a pandemic in June 2009 and ultimately killed over 18,000 people before ending in August 2010. Symptoms of influenza A include fever, sore throat, cough, and sometimes vomiting or diarrhea.