Rome - Countries in West Africa, which have been hard hit by the Ebola virus, may soon be battling with a serious bird flu crisis, the United Nations Food and Agriculture Organisation (FAO) warned on Monday.The H5N1 bird flu virus is highly contagious and is transmittable to humans. According to the World Health Organisation, 447 people across the world have died from it since 2003. The most serious situation is currently in Egypt, with 133 human cases and 37 deaths this year."Avian flu [in West Africa] could trigger a mass die-off of chicken - a nutritious and inexpensive source of food for many people - with detrimental impacts on diets and on the economy of the region, exacerbating an already difficult situation," FAO said."Urgent action is needed to strengthen veterinary investigation and reporting systems in the region and tackle the disease at the root, before there is a spillover to humans," Juan Lubroth, Chief of FAO's Animal Health Service Division, said.The Rome-based UN agency launched a 20-million-dollar fundraising appeal for prevention and response activities.FAO said the H5N1 virus was first detected in West Africa in 2006 and eradicated two years later.It reappeared in Nigeria in late 2014, has spread to Burkina Faso, Niger, Ivory Coast and Ghana, leading to the death by culling or from infection of more than 1.6 million birds, and may infect also Benin, Cameroon, Mali and Togo."We're looking at a disease - H5N1 - that has already spread to five countries in six months. We have to make a concerted effort to stop it in its tracks and we have to do it now," Lubroth, the FAO executive, said.