Nov 19, 2012 (CIDRAP News) – 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.
Officers in Indonesia's Participatory Disease Surveillance and Response (PDSR) program visited 1,078 villages in May, of which 62 (5.8%) were infected, the report says. Fifty-seven of the 62 infections were new. Over the preceding 12 months, about 5.5% of villages visited were classified as newly infected, the FAO reported.
In China, three poultry H5N1 outbreaks were reported in three provinces, while five wild-bird cases were reported in Hong Kong, the report says.
Since 2011 China has had an apparent increase in outbreaks in several northern provinces and other areas outside the identified high-risk zones in the south and east, the FAO said. It said more investigation is needed to uncover the reason for the increase.
The agency reported the following about other countries and regions:
- Bangladesh and India had one outbreak apiece, but the pattern of outbreaks in India suggests that H5N1 may be endemic in some regions.
- Vietnam officially reported no outbreaks, but the virus may be endemic in the southern part of the country.
- No outbreaks were reported in the Middle East. The last one in that region was reported in Israel in the first quarter of this year.
- The last wild bird outbreak in Europe was reported in Russia in June 2010.
- The last country to see its first H5N1 outbreak was Bhutan in February 2010.
The report says that nine confirmed human cases of H5N1 illness were reported in the second quarter of 2012 in four countries: Cambodia, China, Egypt, and Indonesia.
So far this year, 30 human H5N1 cases and 19 deaths have been reported, with the most recent case reported in Indonesia in August, according to the World Health Organization (WHO). In 2011 there were 62 cases with 34 deaths.
FAO's H5N1 global overview for April through June
WHO H5N1 case count