The H5N1 strain has been circulating across the vast expanse of the Earth for more than a decade, occasionally causing human fatalities. H5N1 has already proven its killing capabilities. More than half of the 600 people who were infected have died. But in almost all cases, their infection was due to contact with birds. H5N1 does not seem to transmit efficiently from human to human. The key question is – why? The first proposed explanation could be that the virus is just not capable of morphing into a highly transmissible strain; the second could be that it would take too many mutations to make it possible.
In 2012, new research suggested that only a few changes in the haemagglutinin on the viral surface sufficed to make the virus transmissible through sneezing and coughing between ferrets. This work shows that the first hypothesis is likely to be simply wrong. There are some H5N1 viruses that might require as few as three mutations to become aerosol transmissible from mammal to mammal. However, to make predictions about the pandemic potential of H5N1, a lot of science needs to be done. We need more surveillance, particularly in the regions where some of the mutations are already present. We need to study possibilities of mutations in non-human mammals and we need to do deep sequencing.But there is a substantial risk that H5N1, which so far has not infected many people, could eventually set off a pandemic.