The World Health Organization (WHO) has confirmed the child who contracted Australia's first human case of a "severe" subtype of bird flu was likely exposed during a trip to India last month.

The WHO said on Friday, local time, that genetic sequencing showed the avian influenza virus was H5N1 — a strain that circulates in South-East Asia and has been detected in previous human infections and in poultry.

"Although the source of exposure to the virus in this case is currently unknown, the exposure likely occurred in India, where the case had travelled, and where this clade of A(H5N1) viruses has been detected in birds in the past," it said in a statement.The two-year-old girl from Victoria had travelled to India's western city of Kolkata from February 12 to February 19, returning to Australia on March 1, the WHO said.

The child was hospitalised on March 2 and remained there for more than two weeks before making a "full recovery", according to Victoria's health department. 

The WHO said, as of May 22, no close family contacts in Australia or India had developed symptoms."Additional information provided by the family indicates that the case did not travel outside of Kolkata, India, and did not have any known exposure to sick persons or animals while in India."

Victoria's Chief Health Officer, Clare Looker, had previously said it was unclear how the child had picked up the virus, but noted when humans contracted H5N1, it was usually from exposure to poultry."So either visiting poultry farms or live wet markets, which have birds at them, or if they've had a lot of contact with domesticated birds," she said.

"Occasionally, people can also get it from handling the meat or eggs of infected birds."We couldn't identify a clear event that led to this child's infection, but we suspect it's one of those things."
Amesh Adalja, an infectious disease expert at the Johns Hopkins Center for Health Security, said while it would be difficult to do months after the fact, an investigation was needed to see if the child was in contact with poultry or other birds.

"H5N1 viruses do not transmit efficiently between humans and I suspect there's an occult animal exposure that led to the infection," Dr Adalja said.

WHO advises against travel restrictions

The WHO said human infection of H5N1 can cause "severe disease" and has "a high mortality rate". From 2003 to 2023, a total of 246 cases of human infection with H5N1 have been reported from four countries within the western Pacific region, according to the WHO. Of these cases, 138 were fatal.

"These A(H5N1) influenza viruses, belonging to different genetic groups, do not easily infect humans, and human-to-human transmission thus far appears unusual," the WHO said.
"As the virus continues to circulate in poultry, particularly in rural areas, the potential for further sporadic human cases remains."The organisation advised the public to avoid contact with high-risk environments such as live animal markets and farms, as well as live poultry or surfaces that might be contaminated by poultry droppings.

"WHO advises against implementing travel or trade restrictions based on the current information available on this event," it said. "WHO does not advise special traveller screening at points of entry or other restrictions due to the current situation of influenza viruses at the human-animal interface."
It said any person who had exposure to potentially infected animals or contaminated environments, and who felt unwell, should seek health care promptly and limit exposure to others.