Cambodia looks into human cases of bird flu

Cambodia has reported two cases of bird flu infection in people, a father and daughter in a village in the country’s Prey Veng province. The 11-year-old girl died earlier this week.

The cases, the first reported in Cambodia since 2014, have raised fears the virus has acquired the ability to spread among people and may trigger another pandemic. The Cambodian government is testing 11 other people, four of whom have flu-like symptoms, for infection with the H5N1 flu virus.

The 49-year-old father has tested positive but was not showing any symptoms, according to the health ministry. The World Health Organization is working closely with the Cambodian government to determine whether the father and daughter each acquired the virus by direct contact with infected birds — the most likely possibility — or whether they infected each other.

Experts urged caution, noting there have been hundreds of sporadic cases of H5N1 infection in people since the virus was first identified but no evidence it has become particularly well adapted to humans.

Transmission among people is “very, very rare, versus a common source of infection,” said Richard Webby, a bird flu expert at St. Jude Children’s Research Hospital in Memphis, Tenn., and an adviser to the WHO.

But people should take care to avoid contact with wild birds that may be infected, Webby said.

“The risks from this virus to your average person on the street right now is very low, but it’s not zero,” he said. “And that’s primarily because there’s just so many more infected birds around right now.”

Bird flu, or avian influenza, is a group of flu viruses that are primarily adapted to birds. The particular virus in these new cases, called H5N1, was first identified in 1996 in geese in China, and in people in Hong Kong in 1997.

Since then, there have been nearly 1,000 cases in people in 21 countries, but the vast majority have resulted from prolonged, direct contact with birds. H5N1 does not yet seem to have adapted to spreading efficiently among people.

“At the end of the day, this is a continuum of the same outbreak that started back in 1996,” said Dr. Malik Peiris, chief of virology at the University of Hong Kong, who has helped oversee responses to several bird flu outbreaks in Southeast Asia. “Really, it never went away.”

H5N1 is typically carried by aquatic birds, such as ducks, which can transmit the virus to domestic poultry via feces, saliva or other secretions.

The current version of the virus has been unusually widespread, causing the largest ever bird outbreaks in the United States, where it has affected 58 million farmed birds, and Europe.

It is now considered endemic in several countries in Asia and Europe, according to Webby.

The virus has taken a heavy toll on wild birds, triggering mass die-offs, and it has been spilling over into mammals, especially scavengers, like foxes, that might feed on infected carcasses.

Any reports of infection in people warrant close investigation to confirm that H5N1 has not yet adapted itself to human-to-human transmission. There have been six cases of H5N1 reported in people since September, according to the WHO.