There are three common types of influenza virus, A, B, C. The A type which includes avian flus, is the most common. The B type also occurs in humans.
The usual influenza shot contains antibodies against Type A and Type B virii.
The sub-types are designated based upon the distribution of certain proteins in the viral shell. The are expressed in the form H?N?. H can run 1-16 and N can run 1-9, giving a large mathematical universe of potential sub-types.
About half the H sub-types infect humans, though all of them infect birds. Only three of the N sub-types can infect humans at this time, N1, N2 and N7. The bird flu everyone is afraid of is properly shown as A)H5N1.
Within any sub-type, H5N1, you have strains like the one described in this article in the Scotsman.
A)H1N1 is the designation given the Spanish Flu. It was rediscovered in humans in the mid 1970’s but in a new strain that does not produce a pandemic. A fraction of those who had flu in 2005 in the U.S. had A)H1N1.
The current A)H5N1 is not closely related to the sub-type that produced the Spanish Flu. At any given time, several sub-types and several strains of any given sub-type are in circulation. Flu season is winter in the higher latitudes such as the U.S., but in the tropics it is a year round situation.
Influenza is not normally fatal. In those with a weakened immune system, infants and the elderly it can lead to a bacterial pneumonia which can be fatal. However, in the worst flu pandemic known, the Spanish Flu of 1918-1919, the mortality rate was still about 3% and only about 30% of the U.S. population caught the disease.
The two flu pandemics that followed produced fewer deaths. In 1957 the Asian Flu was A)H2N2. In 1968 it was the Hong Kong Flu, A)H3N2.
Pneumonia is treatable with antibiotics, and we have a variety of other medical treatments that we did not have in 1918. We also have the pneumonia vaccine which will prevent a number of bacterial pneumonias, further reducing your chances of death or serious illness.
