infections
Influenza (Flu)
Influenza epidemics and pandemics
In aninfluenza epidemic,many people get sick within a very brief period of time. Every year, throughout the world, widespread outbreaks of influenza occur during late fall or early winter in temperate climates (called seasonal epidemics). Influenza epidemics may occur in two waves: First, in schoolchildren and the people who live with them Secondly, in people who are confined to home or who live in long-term care facilities, mainly older people In each epidemic, usually only one strain of influenza virus is responsible for the disease. Aninfluenza pandemicrefers to an outbreak that has spread across a large region, typically across continents and sometimes even worldwide. There have been only 6 major influenza pandemics since 1889. An influenza pandemic is concerning because it usually occurs only when there has been a larger than usual change in the strain of influenza virus. When such a large change occurs, that strain of influenza may affect many more people and cause more severe illness. The risk of death is higher. Although no one knows for certain, scientists think the 1918 influenza pandemic caused 30 to 50 million deaths worldwide, including about 675,000 in the United States. In 2009–2010, there was an epidemic of the H1N1 strain of influenza virus (see Influenza types and strains ) that became widespread and was considered a pandemic. This strain had a combination of genes from pig (swine), bird, and human influenza viruses. Because the first reports focused on the swine component, it was referred to publicly as "swine flu," although it was not acquired directly from pigs. People acquired this influenza virus infection from other infected people (person to person spread) like ordinary flu. 