So far H5N1, or Bird Flu, has only infected those directly in contact with affected poultry. But should the virus mutate and become contagious between people, the picture would be very different. To get a better idea of just what we could expect, scientists have created a mutation that permits the virus to infiltrate human lungs. Professor James Paulson of The Scripps Research Institute in California lead a team of researchers who worked on a key protein that is scattered over the virus’ surface, binding it to the cells it is infecting. They stopped short of modifying the virus itself. Doing so could potentially unleash a global pandemic should the modified virus escape or be released. The ‘Journal of Public Library of Science Pathogens’ published their study which states that, unlike the proteins that bind the virus to host cells in its natural state, the mutant protein latched onto human tracheal cells, indicating that the alterations to the protein’s genetic programming had caused the virus to turn its focus from bird to human cells. Prof Paulson said that avian flu viruses coated with the changed haemagglutinin may be able to infect human cells in the same way as human influenza – but while possible, this is thankfully very unlikely. Quoted in the UK’s ‘Independent’ newspaper, he explains why, ‘It’s very easy for a virus to make a single mutation, and two is much more difficult. To make three is even more difficult. We take some comfort in the fact it took three mutations to really make the transformation.’ In the same article Professor Wendy Barclay, Chair in Influenza virology at Imperial College London, poses the question, could the virus recapitulate this switch in nature? The work to identify what mutations the virus has to undergo before it becomes infectious between humans is essential and, explains Prof Barclay, may help to produce a vaccine that could prevent a pandemic on the scale of the Black death. Seventy-five million people were killed in the 14th century and while scientific and health care advances provide us with greater resources than ever before, vaccines would prove key in our armoury. ‘Predicting which influenza virus will cause the next human pandemic is both of scientific and public health interest. We can't afford to make vaccines against all of them, so knowing which ones to worry about would allow efforts and funds to be focused,’ she says. The research also threw up another finding that seems to offer comfort. The mutations required to enable the virus to latch onto tracheal cells made the protein less stable and previous studies on H5N1 have shown this instability makes it harder for the virus to switch from one host to another.