The outbreak of a new type of bird flu in China poses a "serious threat" to human health, but it is still too soon to predict how far it will spread, experts have told the BBC.
Of the 126 people known to be infected so far, 24 have died, with many more still severely ill in hospital.
The H7N9 virus has not, however, yet proved able to spread between people – which limits its global threat.
The threat should be "treated calmly, but seriously", researchers advised.
Prof John McCauley, the director of a World Health Organisation (WHO) collaborating centre in the UK, said: "It is unusual to get these numbers.
"The WHO considers this a serious threat, but we don’t know at this stage whether this is going to spread from human to human."
So far nearly all cases have been traced back to contact with poultry.
The last major bird flu, H5N1, made the jump to people in 1997 and killed more than three hundred – yet, it is still unable to spread between humans.
