Spanish flu was one of the harshest historical pandemics in the northeastern Iran, which killed many local people. Its first outbreak in Mashhad dates back to August 3 and 4, 1918. This disease continued until 1920 in successive waves. The death toll of this disease in Mashhad (with a population of 100,000 people at the time) was possibly as high as 3,500. Moreover, this disease caused outbreak...