WHO sees no sign H5N1 infecting humans more easily

JAKARTA (Reuters) - The World Health Organization (WHO) has seen no sign that the H5N1 bird flu virus is infecting humans more easily, despite concerns expressed by a senior Indonesian official, a WHO spokesman said on Wednesday.

"We have not seen any evidence that the virus is becoming more easily transmissible," spokesman Gregory Hartl told Reuters.

He was commenting on remarks in Jakarta by the head of Indonesia's commission on bird flu control that the virus may have undergone a mutation in the country that allows it to jump more easily from poultry to humans.

Indonesia has recorded 79 human deaths from bird flu, the highest in the world, and the country has been struggling to contain the disease because millions of backyard chickens live in close proximity to humans across the archipelago.

"In the past it took exposure of high intensity and density to the virus to get infected. There are now suspicions, early indications that this has become easier," Bayu Krisnamurthi told reporters.

However, he added that the suspicion had yet to be confirmed.

"We would welcome seeing the evidence on which the comments are based," Hartl said, noting that Indonesia had so far this year reported fewer cases than at the same time in 2006.

"In Indonesia, the number of cases has decreased," he said.

A microbiologist at the Indonesian bird flu commission said the suspicions were based on preliminary findings of molecular genetic tests conducted at laboratories in Indonesia.

"Virus samples from poultry cases have increasingly shown a similarity in their amino acid structure to virus samples extracted from humans," Wayan Teguh Wibawan told Reuters.

"This makes it easier for the virus to attach to human receptors," he said, referring to receptor cells lining the human throat and lungs.

For the H5N1 virus to pass easily from bird to human, it would have to be able to readily attach itself to these special cells.

For the moment, because H5N1 is a bird virus, it has evolved to easily attach to these receptors in poultry. Humans have a different type of receptor site, making it harder for people to become infected.

Wayan said he had spotted "gradual changes" in the virus sample he receives every month. He did not give details on these gradual changes.

Lo Wing-lok, an infectious disease expert in Hong Kong, said changes such as these demonstrated how important it was for Jakarta to share virus samples.

"Are they going to share these samples with overseas labs? These must be confirmed and the world must be forewarned if there has been such an important change," Lo told Reuters in Hong Kong.

"If there is such a change, it would not only mean that the virus can jump more easily from bird to man, but from human to human, too."

Although it mainly affects poultry, scientists fear the H5N1 virus could mutate to become more easily passed between people and trigger a pandemic in which millions could die.

There have been 188 deaths globally from H5N1 and 310 known infections in total, according to World Health Organization data.

(Additional reporting by Richard Waddington in Geneva and Tan Ee Lyn in Hong Kong)