Three more cases have been announced of a new form of influenza, previously found only in birds, in Hong Kong.
From Hong Kong, Jill McGivering reports.
An influenza virus, previously found only in birds, was first detected in a child who died in Hong Kong in May.
Now the announcement of further infections has confirmed fears this was not an isolated case.
Health officials announced on Saturday a 54-year-old man and a 13-year-old girl have both contracted the new strain of flu, classified as H5N1.
The man has already died but the girl is being treated in hospital.
This means four cases have now been found. A two-year-old boy survived the virus last month, while in May a three-year-old boy died after becoming the first known carrier.
The same virus killed 4,500 chickens on Hong Kong farms in the first months of the year but scientists are still unclear how the virus crossed to people.
Hong Kong officials say an urgent meeting is planned for Sunday of a special working group set up to study the new strain of flu.
Health experts from the United States are travelling to Hong Kong to help with the investigations.
One concern is that the virus may have mutated as it entered the human population.
If it has, local people are less likely to be resistant to the flu and the
implications are far more serious.
The discovery of the new strain has sparked international concern, because in the 1950s and 1960s similar viral shifts from birds to humans led to flu pandemics which affected millions of people worldwide.