At one time there was just Hepatitis. Then a cause for it was found, but the cause did NOT explain all Hepatitis, thus we had Type A Hepatitis, and Non-A Hepatitis. We then went on a found another cause for Hepatitis, but again there were cases of Hepatitis NOT explained by this new Cause, thus we ended up with Type A, Type b and Non A Non B. Then Type C was discovered, then type D. And Non A B C D.
Now from what I have read Type E has been known since 1980, but mostly in the third word and unlike Type C, it can disappear on its own. Like Type A, Type E generally causes no long term harm.
From the Center for Disease Control (CDC):
http://www.cdc.gov/hepatitis/index.htmFrom World Health Organizations (WHO):
http://www.who.int/mediacentre/factsheets/fs280/en/Type C first Classified in 1989:
http://www.who.int/mediacentre/factsheets/fs164/en/Type D is know to exist, but apparently only in the presence of Type B:
http://en.wikipedia.org/wiki/Hepatitis_DType E found in 1980,
http://www.who.int/mediacentre/factsheets/fs280/en/http://en.wikipedia.org/wiki/Hepatitis_EType F is suspected to exist but the information in it is rare:
http://en.wikipedia.org/wiki/Hepatitis_F_virusThere is some question if Type G has been found in 1995, a virus was found can called Type G, but it does not appear to cause any harm to humans:
http://en.wikipedia.org/wiki/Hepatitis_Ghttp://content.nejm.org/cgi/content/abstract/336/11/741