5 n-count A medium is a substance or material which is used for a particular purpose or in order to produce a particular effect. Blood is the medium in which oxygen is carried to all parts of the body..., Hyatt has found a way of creating these qualities using the more permanent medium of oil paint.
An influenza pandemic is a global outbreak of disease that occurs when a new influenza A virus appears or âemergesâ in the human population, causes serious illness in people, and then spreads easily from person to person worldwide. Pandemics are different from seasonal outbreaks or âepidemicsâ of influenza.
The influenza virus changes often, so having flu caused by one strain does not give you full immunity to other strains. Widespread outbreaks of the flu usually follow significant changes (called antigenic shifts) in the virus and occur about every 10 years. People who get the flu tend to become much sicker when a shift in the flu virus occurs.