The number of reported H5N1 avian influenza outbreaks in poultry and wild birds has decreased since mid 2011 and was down sharply in the second quarter of this year, the United Nations Food and Agriculture Organization (FAO) said in a quarterly update on the ongoing situation.
Six countries reported a total of 98 domestic poultry outbreaks and 5 wild bird cases or outbreaks from April through June of this year, which was far below the 508 outbreaks reported in the second quarter of 2011, the FAO said. The affected countries were Bangladesh, Cambodia, China (including Hong Kong), Egypt, India, and Indonesia.
The global number of H5N1 outbreaks dropped from 2003 to mid 2008, increased again from mid-2008 to mid-2011, and has dropped since then, according to the FAO figures.
Factors in the second-quarter decline included lower numbers reported from Egypt and Indonesia and an absence of reported outbreaks in countries where the disease has occurred sporadically, such as Japan, South Korea, and Vietnam, the agency reported.
But the FAO cautioned that not all outbreaks are reported, making it difficult to tell if the world has actually made progress in H5N1 control.
"Clinical signs [of disease] can be masked by the use of regular vaccination in poultry populations. As a result, outbreaks are underreported," the report says. Also, some countries have little information on the disease status in their commercial poultry sectors, it adds.
Outbreaks and affected countries were fewer in the second quarter than in the first quarter of this year, which is typical because the April-through-June period generally marks the end of the H5N1 season, the FAO said. From January through March there were 198 outbreaks in 11 countries.
Egypt reported 19 outbreaks in the second quarter, including 15 in mostly unvaccinated household flocks and four in vaccinated commercial flocks, the report says.
Among 374 Egyptian commercial farms where active surveillance was conducted, the virus was found on only three. Active surveillance conducted in household poultry in 103 villages produced two positive samples, the FAO said.
The report also notes that 76 samples from commercial farms in 11 Egyptian governorates tested positive for low-pathogenicity H9 flu viruses.
Indonesia continues to report "a high proportion" of H5N1 outbreaks, but outbreaks in the second quarter were lower than in previous years, the FAO said. Unlike other countries, however, Indonesia counts H5N1 outbreaks at the village level rather than the household level, and the report does not offer specific year-on-year comparisons.