Causes of Flu

Health encyclopaedia - Alphabetical Topic List

| A |

| B |

| C |

| D |

| E |

| F |

| G |

| H |

| I |

| J |

| K |

| L |

| M |

| N |

| O |

| P |

| Q |

| R |

| S |

| T |

| U |

| V |

| W |

| X |

| Y |

The influenza virus family contains three main types, A, B and C. Influenza viruses are known to mutate (change) over time. Also, strains of the flu virus as classified on where and when they were first identified and given a serial number.

Influenza A occurs more frequently (every two to three years) and is more serious. It is very likely to mutate and it regularly produces varieties to which populations have no resistance. It is for this reason that widespread epidemics occur that may affect whole continents (pandemics). These are caused by new strains of type A virus.

Generally, influenza B causes a less severe illness, although it is responsible for smaller outbreaks.

Type C usually causes a mild illness similar to the common cold.

In recent years, two subtypes of influenza A have been circulating, The H1N1 subtype and the H3N2 subtype- Panama or Moscow-like strains.
Laboratory testing so far this year (2003/2004) shows that the main strain circulating is a flu A (H3N2) Fujian-like strain. This is slightly different to the A (H3N2) Panama-like virus, which has been circulating in the UK in recent years.