The World Health Organization said Friday it was impossible to say whether a case of bird flu in China involving a 52- year-old man was due to human-to-human transmission - but, even if it was, it was down to very close contact between the victims.
The Assistant Director-General for Health Security at WHO, Dr David Heymann, said the only proven transmission of this nature so far, in Indonesia and Thailand, had been as a result of very "close contact" in a "very circumscribed area."
WHO was still awaiting final tests results for a recent cluster of cases in the north-west region of Pakistan. The team of WHO experts, who travelled to the area earlier this week, believed though that the first-ever human cases in the country were again a result of intimate contact.
Heymann, said the virus could on "occasional instances be transmitted" between humans but it was not transmittable like influenza with a sneeze. "It's not that kind of transmission."
In China, both the man and his 24-year-old son, who died on December 2, had been exposed to the same common source. Infection had also occurred during the incubation period. There had also been close contact with another 600 people but blood tests had confirmed they were free from the virus.
Heymann, said: "Even if there had been human-to-human transmission, it was limited and did not continue. It was not sustained and it's that which is very important."
However though the H5N1 strain of bird flu had not jumped the species barrier in a way that would cause a major outbreak so far, the scientific community remained convinced there was a real possibility of an influenza pandemic in the future but it could not say whether H5N1 would be the source or another flu variant.
TAGS: Health WHObird flu