A 5-year-old Vietnamese boy has been infected by the bird flu virus that has killed 47 people in Asia, but is recovering, doctors said on Friday.

“He’s being treated in isolation and he is recovering very well,” said Bui Duc Phu, deputy director of the Hue Central Hospital in the central province of Thua Thien-Hue.

The boy’s case is the 25th human bird flu infection in Vietnam since December and the first in the central region. Most of the cases have been in the north and 13 have died.

On Thursday, Phan Nhu The, director of the Hue hospital, told Reuters poultry in the boy’s village in the nearby province of Quang Binh had been infected by the H5N1 virus.

He was taken to hospital early this week with damage to his lungs. His 13-year-old sister had died, but she had not been tested for bird flu, The said.

Since December, when the H5N1 virus broke out anew in the Mekong Delta, 35 of Vietnam’s 64 provinces have been affected. In addition to the 13 Vietnamese, one Cambodian has died of it.

A cluster of cases in the northern province of Thai Binh has raised concern about the possibility of human-to-human transmission of the H5N1 virus, which experts fear could mutate into a form that could cause a pandemic.

Among those who have recovered was a 14-year-old Thai Binh girl whose 21-year-old brother is still under intensive care and a male nurse who treated him.

However, the World Health Organization says it has seen no evidence so far to suggest the virus is changing into a form that could be transmitted easily from one human to another.

The avian influenza virus has killed 34 Vietnamese, 12 Thais and the Cambodian and has recurred several times despite the slaughter of millions of poultry since spreading across large parts of Asia in late 2003.