The gene sequences from Ukraine have been released by WHO and are showing that there has been genetic mutation of H1N1, probably on the basis of reassortment. The specific change in gene sequence is the D225G and was recoverd from both lung and throat samples of cases that ended in death. These changes show the development in the H1N1 swine flu the ability to selectivly infect lung tissue causing a massive immune response called 'cytokine storm'. It is the cytokine storm that actually destroys lung tissue and causes death. Cytokine storm is more likely in younger healthy patients who are able to mount a strong immune response, that in fact is too strong. If these changes are the result of reassortment, ie, mixing of different viruses, this may be very disturbing because widespread vaccination has created the perfect background scenario for the wholesale mixing of many differenct viruses within individuals. Isolates from different parts of the world have shown similar changes making it clear that the genie is already out of the bottle.