"There have been fewer cases of the disease this year than last year at the same time, indicating that there is a reduction in overall viral load," said the Food and Agriculture Organisations top veterinarian Joseph Domenech in a news release.
Outbreaks were recorded in 17 countries as of March 15, 2007, Domenech said.
Overall last year, a total of 53 countries had outbreaks of H5N1, which has killed at least 171 people worldwide since its appearance in 2003.
The FAO statement warned that "Egypt, Indonesia and Nigeria have not yet been able to contain the disease, effectively making them reservoirs of the virus for possible introduction to other countries."
The Rome-based agency added: "Despite substantial progress in global efforts to bring the deadly H5N1 avian influenza virus under control, the disease continues to spread to new countries and to new areas in some countries where containment has not been successful."
Domenech said in the statement: "The risk of a pandemic will be with us for the foreseeable future. However, looking on the positive side, many countries have managed to control the disease."
Among positive examples are Thailand, Turkey and Vietnam, which "have been generally successful in containing and controlling the virus," the FAO said, singling out Turkey for "a highly successful control campaign."
Surveillance efforts in Indonesia, which has borne the brunt of the disease with 71 human deaths to date, according to government figures, are "hampered by the countrys large size and geography with some 17,000 islands," the FAO said.
In addition, Jakarta has a "weak national veterinary service, as well as insufficient international and national financial and human resources invested in prevention and control," the statement said.
Egypt "has faced problems containing the disease for a number of reasons, including the lack of compensation to help farmers who lose their poultry to culling," the UN agency said, adding however that Cairo "is revising its strategic plan" in the fight against bird flu.
In Nigeria, "authorities have not been in a position to enforce effective movement control for poultry and poultry products out of infected areas," the FAO lamented.