China has reported the first fatal case of H3N8 bird flu in humans after registering two other non-fatal infections with the disease last year, the World Health Organization (WHO) said late on Tuesday.

The death reported was that of a 56-year-old woman from the southern Chinese province of Guangdong.

The WHO said that a wider spread of the virus between humans was unlikely but nonetheless stressed the importance "of global surveillance to detect virological, epidemiological and clinical changes associated with circulating influenza viruses which may affect human [or animal] health."

What do we know about the fatality?

The woman who died had a number of underlying conditions and was often exposed to live poultry and wild birds, the WHO said.

She fell ill on February 22, was hospitalized with severe pneumonia on March 3, and died on March 16, the WHO said.

It said the source of infection might have been a wet market visited by the woman before she fell ill, as samples collected there had been positive for influenza A(H3).

No cases of infection had been found in anyone who had been in close contact with the woman, the WHO said.

"Based on available information, it appears that this virus does not have the ability to spread easily from person to person, and therefore the risk of it spreading among humans at the national, regional, and international levels is considered to be low," its statement said.

What is the H3N8 virus?

The H3N8 virus is commonly detected in birds but causes few symptoms. It has also infected other mammals, such as horses, dogs, and seals.

The virus is known to have been circulating since 2002 when it was first found in North American waterfowl.

The first recorded human cases are those that have now emerged in China. The two previous cases were reported last April and May, with one person falling critically ill, while the other had only mild symptoms.

China often sees sporadic human infections with bird flu owing to its huge poultry and wild bird populations that often live in close proximity to humans.

Health authorities across the world consider it important to monitor all avian influenza viruses, as they can easily evolve and cause a pandemic.