From H5N1 to HxNy: An epidemiologic overview of human infections with avian influenza in the Western Pacific Region, 2003–2017

Abstract

Since the first confirmed human infection with avian influenza A(H5N1) virus was reported in Hong Kong Special Administrative Region in 1997, sporadic zoonotic avian influenza viruses causing illness in humans have been identified globally, with the WHO Western Pacific Region as one of the hotspots. From November 2003, when a resurgence of H5N1 virus activity in humans and animals occurred, through September 2017, 1,838 human infections with avian influenza viruses in the region were reported to WHO. Viruses infecting humans were A(H5N1), A(H5N6), A(H6N1), A(H7N9), A(H9N2) and A(H10N8). The vast majority of infections were with H7N9 (n=1,562) and H5N1 (n=238) viruses, and most (n=1583, 86%) were reported from December through April. In poultry and wild birds, H5N1 and H5N6 subtypes were the most widely distributed, with outbreaks reported from ten and eight countries and areas, respectively. Regional analyses of human infections with avian influenza subtypes revealed distinct patterns and variations in epidemiology across countries, age, and time. Such epidemiologic patterns may not be apparent from aggregated global summaries or isolated country reports; regional assessment can offer additional insight that can inform risk assessment and response efforts. As infected animals and contaminated environments are the primary source of human infections, regional analyses that bring together surveillance data from human and animal health sectors are an important basis for exposure and transmission risk assessment and public health action. A One Health approach combining sustained event-based surveillance with enhanced collaboration between the human, animal (domestic and wildlife), and environmental sectors will provide a basis to inform joint risk assessment and coordinated response capacities

An epidemiological overview of human infections with HxNy avian influenza in the Western Pacific Region, 2003–2022

“…6 Of the 1838 human infections with A(HxNy) in this report, most were with A(H7N9) (n = 1562, 85%) and A(H5N1) (n = 238, 13%), followed by A(H9N2) (n = 18, 1%) and A(H5N6) (n = 16, 1%). 6 This current report provides an update on human cases of A(HxNy) notified Since the last report, an additional 134 human avian influenza infections were notified from 1 October 2017 to 31 July 2022. In recent years there has been a change in the primary subtypes and frequency of reports of human A(HxNy) in the region, with a reduction of A(H7N9) and A(H5N1), and conversely an increase of A(H5N6) and A(H9N2).…”

“…From 1 November 2003 to 31 July 2022, there were 1972 human infections with nine different A(HxNy) subtypes notified to WHO from the WPR. Since the last report, ( 6 ) 134 additional human AI infections were notified from 1 October 2017 to 31 July 2022, including three new subtypes notified globally for the first time.…”

“…( 6 ) Of the 1838 human infections with A(HxNy) in this report, most were with A(H7N9) ( n = 1562, 85%) and A(H5N1) ( n = 238, 13%), followed by A(H9N2) ( n = 18, 1%) and A(H5N6) ( n = 16, 1%). ( 6 ) This current report provides an update on human cases of A(HxNy) notified from 1 November 2003 to 31 July 2022.…”

Immune Control of Avian Influenza Virus Infection and Its Vaccine Development

“…It evolved from the internal genes of enzootic H9N2 viruses in chickens and H10 and N8 viruses’ surface genes from household ducks. This resulted in three deadly diseases and two fatalities in people [ 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. H10 AIVs have also been detected in mink, seals, mammals and pigs [ 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ].…”

Avian Influenza: Could the H5N1 Virus Be a Potential Next Threat?

“…Multiple H5N1 infections in domestic poultry and wild birds have occurred in more than 60 countries since September 2017, with sporadic human infections occurring in 16 countries [38]. The Italian National Reference Center (CRN) for avian influenza and Newcastle disease (based in Rome, Italy) confirmed the first positivity for highly pathogenic avian influenza virus (HPAIV) subtype H5N1 in poultry on 22 September 2022.…”