The three last pandemic strains of influenza A virus-Asian/57, Hong Kong/68 and Russian/77-are believed to have originated in China. The strains responsible for the 1957 and 1968 human pandemics were reassortants incorporating both human and avian influenza viruses, which may have arisen in pigs. We therefore undertook a population-based study in the Nanchang region of Central China to establish the prevalence, types and seasonal pattern of human influenza infection and to screen serum samples from animals and humans for evidence of interspecies transmission of influenza viruses. Two definite influenza seasons were demonstrated, one extending from November to March and the other July to September. The profile of antibodies to commonly circulating human influenza viruses was no different in Nanchang and neighboring rural communities than in Memphis, Tennessee, USA. In particular, Chinese women who raised pigs in their homes were no more likely to have been exposed to influenza virus than were subjects who seldom or never had contact with pigs. However, we did obtain evidence using isolated H7 protein in an enzyme-linked immunoabsorbent assay for infection of pig farmers by an avian H7 influenza virus suggesting that influenza. A viruses may have been transmitted directly from ducks to humans. The results of the serological survey also indicated that pigs in or near Nanchang were infected by human H1N1 and H3N2 influenza viruses, but not with typical swine viruses. We found no serological evidence for H2 influenza viruses in humans after 1968.
AdolescentAdultAnimalsAntibodies, ViralCell LineChick EmbryoChickensChildChild, PreschoolChinaDogsDucksFemaleHumansInfantInfluenza A virusInfluenza in BirdsInfluenza, Human
Structured evidence records
Evidence records
8 total
Serological Evidence3 records
Serological EvidenceExtraction confidence 1.00
Key finding
Enzyme-linked immunoabsorbent assay detected antibodies to an avian H7 influenza virus in pig farmers, suggesting transmission from ducks to humans.
We did obtain evidence using isolated H7 protein in an enzyme-linked immunoabsorbent assay for infection of pig farmers by an avian H7 influenza virus suggesting that influenza A viruses may have been transmitted directly from ducks to humans.
Method
enzyme-linked immunoabsorbent assay
Sample type
serum
Serological EvidenceExtraction confidence 1.00
Key finding
Serological survey revealed that pigs in or near Nanchang had antibodies to human H1N1 and H3N2 influenza viruses, indicating infection of pigs by human strains.
The results of the serological survey also indicated that pigs in or near Nanchang were infected by human H1N1 and H3N2 influenza viruses, but not with typical swine viruses.
Sample type
serum
Serological EvidenceExtraction confidence 1.00
Key finding
Serological survey revealed that pigs in or near Nanchang had antibodies to human H3N2 influenza viruses, indicating infection of pigs by human strains.
The results of the serological survey also indicated that pigs in or near Nanchang were infected by human H1N1 and H3N2 influenza viruses, but not with typical swine viruses.
Sample type
serum
Spillover Event3 records
Spillover EventExtraction confidence 0.95
Key finding
Serological assay detected infection of pig farmers by an avian H7 influenza virus, supporting direct transmission from ducks to humans in China.
We did obtain evidence using isolated H7 protein in an enzyme-linked immunoabsorbent assay for infection of pig farmers by an avian H7 influenza virus suggesting that influenza A viruses may have been transmitted directly from ducks to humans.
Method
enzyme-linked immunoabsorbent assay
Study design
serological survey
Transmission direction
animal-to-human
Geographic raw
Nanchang region of Central China
Country inferred
China
Spillover EventExtraction confidence 0.95
Key finding
Pigs in or near Nanchang were found seropositive for human H1N1 and H3N2 influenza viruses, demonstrating human-to-swine transmission.
The results of the serological survey also indicated that pigs in or near Nanchang were infected by human H1N1 and H3N2 influenza viruses, but not with typical swine viruses.
Study design
serological survey
Transmission direction
human-to-animal
Geographic raw
Nanchang
Country inferred
China
Spillover EventExtraction confidence 0.95
Key finding
Pigs in or near Nanchang were infected by human H3N2 influenza viruses, indicating human-to-swine spillback infection.
The results of the serological survey also indicated that pigs in or near Nanchang were infected by human H1N1 and H3N2 influenza viruses, but not with typical swine viruses.
Study design
serological survey
Transmission direction
human-to-animal
Geographic raw
Nanchang
Country inferred
China
Zoonotic Surveillance2 records
Zoonotic SurveillanceExtraction confidence 0.90
Key finding
Serological surveillance in Nanchang, China revealed that pigs were infected by human H1N1 and H3N2 influenza A viruses.
The results of the serological survey also indicated that pigs in or near Nanchang were infected by human H1N1 and H3N2 influenza viruses, but not with typical swine viruses.
Method
serological survey
Sample type
serum
Geographic raw
Nanchang
Country inferred
China
Zoonotic SurveillanceExtraction confidence 0.90
Key finding
Serological evidence among pig farmers in Nanchang, China indicated infection by an avian H7 influenza virus, suggesting possible duck-to-human transmission.
We did obtain evidence using isolated H7 protein in an enzyme-linked immunoabsorbent assay for infection of pig farmers by an avian H7 influenza virus suggesting that influenza A viruses may have been transmitted directly from ducks to humans.
Method
enzyme-linked immunoabsorbent assay
Sample type
serum
Geographic raw
Nanchang
Country inferred
China
Citation context
References
20 references
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