How many types of cold and flu virus are there?

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There are basically three types of flu: A, B and C, but there are many types of cold viruses, known as Rhinoviruses.  Each type can have many strands and subtypes, however, the flu virus often mutates.  The type A virus has two strands, A and B.  Each strand also has subtypes (currently 9 for NA and 16 for HA).  Type A influenza is the one most likely to spread the endemics.  Type C is the least deadly and often only causes manageable respiratory infections.  

Depending on how cold viruses are identified, ther are currently about 300 or 32,000 different cold viruses identified, and it is very difficult to develop a vaccine to cover all of them. 

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