Usually most people have heard of influenza, or in other words the flu. The flu is a contagious respiratory illness caused by influenza that infect the nose, throat, and even the lungs. There are three different types of the influenza virus which are: influenza A, influenza B, and influenza C. Influenza A is the most common one to humans. Most of the time with the flu you would only get a mild to severe illness, but at times it could lead to death. There is really no way of preventing getting the flu, but to lessen your chances you could always get the flu vaccine. There are a lot of different symptoms that come along with the flu like: a fever, cough, sore throat, runny nose, muscle or body aches, headaches, fatigue, and sometimes even vomiting. It’s also important to known that not everyone will get a fever with the flu. Most experts believe that the virus is spread between people that have the flu when the cough, sneeze, or talk. Sometimes, you could get the flu just from touching a surface that the flu virus is on. If you have the flu and don’t know you do, you can still give it to someone. People with the flu are most contagious in the first three to four days after the illness begins. Some people could also be contagious a day before symptoms even show up and five to seven day after the symptoms. Some people with not as strong immune systems, like children, might be able to infect people even longer than seven days. The average time of having the flu is one to four days, but averages out being around two. There is no way to cure the flu, but there is things to help to help prevent getting it. The things most people is going to get the seasonal flu shot. The seasonal flu shot usually contains two strains of the Influenza A virus and one or two strains of the Influenza B virus. The strains in the vaccine are the same for all types of influenza in a given year, but might change from year to year. Influenza is a virus that has hundreds of different strains. These strands are separated into groups known as Influenza A, B, and C. Influenza A is the one that is most common for humans. The influenza A virus is broken down into further groups known as H and N subtypes. So if you see anything like “H#N#,” it is influenza A. There are many different types of subtypes, but there are only three different combinations. There are sixteen H subtypes and nine N subtypes. Other combinations have been found, but are only found in animals such as pigs and birds. The three combinations that are mostly found in humans are H1N1, H2N2, and H3N2. Even in those types, the influenza virus can mutate and change every year. Because of this, there are four different ways to name the influenza virus. The four ways are: the host of the origin, the geographical location of origin, the strain numbers, and the year of discovery. When the CDC (United States Centers for Disease Control and Prevention) and the WHO (World Health Organization) name a new strain of influenza virus they have certain steps. First they start with the group of influenza that is falls in, so like A, B, or C. Next they will name the host, location of origin, strain number, year of discovery, and H-N subtypes in parentheses. An example of an Influenza A virus would look like this: A/duck/Alberta/35/76/ (H1N1). That reads that the virus of a duck origin was identified in Alberta, Canada, with the d’train number 35, in the year of 1976. Mostly all of the major flu pandemics in modern history were caused by Influenza A viruses. The 1918 pandemics, which for some people is also known as the Spanish Flu, was caused by the H1N1 virus. The 1957 flu pandemics, also known as the Asian Flu, was caused by an H2N2 virus. The 1968 pandemics, which was called the Hong Kong flu, was caused by and H3N2 virus. Finally, the 2009 pandemics, called the swine flu, was caused by a novel H1N1 virus.