The H1N1 virus is a pandemic but at the moment it is still less deadly than the normal seasonal flu. The fear though is that it will become a fast-mutating bug that becomes impossible to combat with drugs - much like the Spanish flu in 1918. Now a Japanese teenager has been found carrying a version of the virus that's resistant to treatment by Tamiflu, one of a handful of drugs used for the treatment of H1N1. But apart from the anti-virals, there are now different vaccines. Al Jazeera's Dan Nolan explains.
