While the new cases of swine flu in the UK would appear to be decreasing, news from Northern Europe indicates that the H1N1 virus has mutated. Norway has already seen more fatalities as a proportion of the total population than other European countries. Norwegian health authorities announced at the end of November that they have discovered a potentially significant mutation in two patients that appears to enable the virus to bury deeper into the respiratory tract. The cases so far would indicate that the virus has spontaneously mutated in the individual cases, rather than a single mutation in one person then being passed through the population.

There are also reports that the virus may have developed a resistance to Tamiflu, the drug of choice in combating the viral infection.

The success of a virus depends on the ability of the virus to avoid attack by the body's immune system before it has been able to substantially replicate and to escape from the bombardment of therapeutic drugs. H1N1 is showing signs of doing both.