Recent research studies highlighted the danger of H5N1 mutation into a form readily transmissible between mammal species, namely ferrets [ 11- 13], demonstrating potential transmissibility between humans.
The critical phase that presages a pandemic is when the virus mutates, becoming readily transmissible between humans.
"The mutations... could cause the viruses to be more transmissible between humans," Peter Palese, a prominent microbiologist at Mount Sinai School of Medicine, wrote recently.
Infection across Africa would increase the likelihood that the virus will mutate to become transmissible between humans.
Dr Fouchier is the head of one of two groups studying how bird flu might become transmissible between people.
His experiments found that the natural version of the H5N1 virus, which is currently circulating in flocks of birds around the world, needs only five mutations in its genetic sequence to become potentially transmissible between people.
The only way to figure that out was to take those mutations and see if they can make the H5N1 virus airborne as well – in other words, make it transmissible between people via a cough or sneeze.
The more serious 1918 pandemic was caused when a bird flu virus adapted on its own to become transmissible between humans.
In 2011 scientists reported the development of a version of H5N1 that had been genetically altered to make it transmissible between ferrets, which respond to influenza in much the same way that humans do.
"However, continued monitoring for this is critical," said Dr Keiji Fukuda, WHO Assistant Director-General for Health Security, adding that studies of the virus had not shown it to have changed "to make itself more transmissible" between humans.
A international team of experts led by the WHO has conducted a five-day investigation in China but said they were no closer to determining whether the virus could become transmissible between people.
