OIE Report 19th February 2009
One outbreak of low pathogenic Avian Influenza (LPAI) of the subtype A(H5N3) has been reported to the OIE by the Romanian authorities in a group of animals (17 ducks and 2 geese) introduced as sentinel birds in the Danube Delta. These animals were infected after being in contact with wild birds in the Delta. The presence of subclinical disease was initially confirmed on the 7th of February by means of RT-PCR in two different laboratories, including the Veterinary Laboratories Agency at Weybridge, UK (OIE’s Reference Laboratory). Because the source of the outbreak is inconclusive, the Romanian authorities have applied contention measures appropriate to this situation, including control of wildlife reservoirs, screening, stamping out and movement control inside the country.
ECDC comment (24th February): The strain of avian influenza identified in this outbreak is of the H5 type but it is classed as low pathogenic in birds. Low pathogenic avian influenza can occasionally convert to a highly pathogenic form but that cannot happen here to produce an A(H5N1) type as the N1 subtype has been specifically excluded.
A conclusion from previous ECDC risk assessments is that most low pathogenicity avian influenza viruses to date are poorly adapted to humans and hence have limited ability to transmit from birds to humans. However past incidents have demonstrated the zoonotic potential that some low pathogenic viruses can present to humans. [1, 2] It also must be remembered that the terms highly pathogenic and low pathogenic relate to the impact of these viruses in birds and do not necessarily mean that a virus is highly pathogenic or of low pathogenicity for humans. Hence it is prudent that those that may have been exposed to any avian influenza virus take precautions to limit the potential risk of infection. These are similar to those recommended for highly pathogenic avian influenza.[3, 4] However quite reasonably some national authorities relax rules (for example not insisting on persons taking antivirals prophylactically but only as treatment) where it is known that there are few implications for human health as is the case in A(H5N3) viruses.
1) Influenza team (ECDC). Low Pathogenicity Avian Influenzas and human health. Euro Surveill. 2007;12(22):pii=3209. Available online
2) Editorial team. Avian influenza A/(H7N2) outbreak in the United Kingdom. Euro Surveill. 2007;12(22):pii=3206. Available online
3) ECDC Who is at risk of acquiring bird flu – May 2006
4) ECDC Technical report. Minimise the risk of humans acquiring highly pathogenic avian influenza from exposure to infected birds or animals. Version December 21st 2005