At the Costain live animal market in Nigeria’s main city of Lagos chickens, turkeys and geese are still crowded together in the portable coops they arrived in from upcountry. Teenage boys helping buyers kill, clean and cut up the birds still do so with knives and bare hands, unprotected by gloves or face masks.

More than one year after Nigeria reported sub-Saharan Africa's first cases of the deadly H5N1 avian flu virus and one month after the illness claimed its first human life in the country, little has changed in the way birds are handled or slaughtered.

But old habits need to change and control measures must be improved in markets and on farms if Nigeria is to the curb the worsening spread of the virus, the Food and Agriculture Organisation (FAO) said on Tuesday.

Poultry in at least 19 of Nigeria's 36 states have been infected by bird flu, according to the government. The FAO said its recent mission to Nigeria found that the virus was still spreading, with the most probable means being traders moving poultry across the country.

The agency warned that neighbouring countries were at risk and said urgent surveillance measures were necessary to stop the disease from spreading across Nigeria’s borders into Benin, Niger, Chad and Cameroon.

“The first confirmed case of H5N1 infection in humans in Nigeria shows that there is a continuing danger of human exposure to the virus from high-risk practices, such as handling sick or dead chickens, and especially from unsafe slaughtering of poultry at home or in markets,” said Joseph Domenech, chief veterinary officer of FAO, in a statement.

The FAO sent a team to help Nigeria, Africa’s most populous country, after local health authorities reported that a 22-year-old woman had died on 17 January from avian flu. Subsequent tests by the World Health Organisation (WHO) confirmed the Nigerian diagnosis, prompting investigation of the woman's mother who had died weeks earlier.

Tony Forman, leader of the FAO mission to Nigeria, said initial tests did not show the victim's mother also died of bird flu, although WHO and the US Centres for Disease Control were conducting further investigations. The FAO team was also unable to determine the exact source of the bird flu infection beyond the fact that it probably came from live chicken the young woman bought from a Lagos market just before Christmas.

“We believe the source of the virus was poultry purchased from a Lagos market,” Forman told IRIN. “It's been a long time now. The prospect for determining where this (virus) came from is now virtually impossible,” he said, citing wild migratory birds and legal and illegal imports as possible sources.

The major challenge facing Nigeria, Forman said, was to quickly obtain information about where the virus was and where it might be spreading in order to curtail it.

Despite the government's efforts, experts say more still needs to be done to effectively curtail the spread of the virus that scientists fear could mutate into a strain that could be easily transmissible between humans and cause a global pandemic. So far, 167 people have died from avian influenza worldwide.

“I think the government is doing a good job,” said Forman of the FAO. “But they need additional support to get a better control of this disease.”