The World Health Organisation (WHO) has disputed claims that it has exaggerated the risk of a human influenza pandemic.
The agency has predicted that as many as 7.4 million people could die if a pandemic sweeps the world.
Lee Jong-Wook, director-general of the WHO, says the threat of a pandemic is real and the agency is not guilty of exaggerating the case.
Lee was speaking at a meeting in Geneva to the organisation's executive board.
Lee said the only way to reduce the devastating human and economic impact of a pandemic is to take the threat seriously now and prepare for it.
He says the problem is a global one.
Meanwhile China has reported it's 10th case of the potentially fatal bird flu virus. The health ministry says the woman is in a critical condition in hospital.
She apparently ran a shop in a farm goods market in the Sichuan Province.
To date six of China's 10 known victims of bird flu have died.
The WHO has also confirmed bird flu as the cause of death of a young brother and sister in Indonesia this month, taking the death toll to at least 82 since 2003.
Bird flu remains a disease primarily in birds and victims contract the virus through close contact, usually with sick chickens.
Experts have always feared the virus might mutate into a form that would pass easily from person to person, sparking a pandemic.
Only last week wealthy nations pledged $1.9 billion to fight bird flu at a conference in Beijing.
The money will be spent on measures to eradicate a virus which is endemic in poultry in parts of Asia.