The Varying Types of the Flu
The flu is caused by varying strains of the flu virus. The flu is divided into 3 major types (A, B, and C) with each of these types being further divided into differing strains. Influenza A infects mostly humans and birds, though it also affects pigs. Prolonged and close interaction between humans and other animals, such as chickens, allow for the virus to mutate and jump from species to species. For example, in Southeast Asia, open-air markets with cages of chickens are a common sight. This allows for ample close interaction with humans and is why the bulk of localized influenza A virus pandemics occur or begin in Southeast Asia. Because influenza A mutates quickly, a seasonal flu shot is recommended every year. It also explains why vaccines do not offer protection from year to year.
Commonly-known strains of influenza A are:
- Spanish Flu – The Spanish Flu of 1918 was one of the most devastating pandemics in modern history. It was the first of two pandemics involving the H1N1 strain of influenza.
- Swine Flu – Swine Flu is another variation of the H1N1 strain of influenza. Related to the Spanish Flu strain, this subtype of influenza A caused a pandemic in 2009 and continues to circulate among the population. Like its 1918 predecessor, this variation is particularly problematic as it disproportionately affects young adults and otherwise healthy people. Older persons, particularly those over the age of 60, are usually the most affected by the flu; however, they seem to have some antibodies against this variation.
- Bird Flu – Bird Flu originates, as its name suggests, in birds such as chickens or ducks. The virus then mutates and infects humans from interaction with a contaminated bird. The majority of these cases occurred in Asia and has remained relatively local. There is much concern that this H5N1 variation will make a permanent leap from birds to humans and cause a serious global pandemic as there is little resistance to Bird Flu. Currently transmission from person-to-person has only been documented in extremely rare cases.
Influenza B infects mainly humans. This type is less common that influenza A. Because it does not mutate as quickly as influenza A, it is typically not to blame for the yearly need for a flu vaccine. It also does not cause pandemics and only has mild symptoms. Influenza C is even rarer than types A or B and typically results in only a mild case of the flu. Influenza C does not cause pandemics. The flu vaccine most often protects against two types of influenza A virus and one type of influenza B virus.
