Epidemiology and Infection

Research Article

An epidemiological study of influenza viruses among Chinese farm families with household ducks and pigs

L. L. Shua1, N. N. Zhoua1a2, G. B. Sharpa1a3, S. Q. Hea2, T. J. Zhanga2, W. W. Zoua2 and R. G. Webstera1 c1

a1 Department of Virology/Molecular Biology, St. Jude Children's Research Hospital, 332 North Lauderdale, P. O. Box 318, Memphis, TN 38101, USA

a2 Department of Microbiology, Jiangxi Medical College, 162 Ba Yi Road, Nanchang, Jiangxi, China

a3 Department of Hematology/ Oncology, St. Jude Children's Research Hospital, 332 North Lauderdale, P. O. Box 318, Memphis, TN 38101, USA

Abstract

To examine the possibility of interspecies transmission and genetic reassortment of influenza viruses on farms in Southern China, we surveyed 20 farm families living outside the city of Nanchang who raised pigs and ducks in their homes. Weekly interviews of family members and virus isolation studies of throat swabs and faecal samples, collected from September 1992 to September 1993, established the seasonal pattern of respiratory tract infections in these families and identified 11 influenza viruses (6 in humans and 5 in ducks). Most of the human isolates were type A of H3N2 subtype. Serologic studies of farm pigs indicated infection by the same human viruses circulating in family members, but there was no evidence that either swine or avian viruses had been transmitted to pigs. Eight of 156 human serum samples inhibited the neuraminidase activity of two of the duck isolates, raising the possibility of interspecies transmission of these avian viruses. Genotype analysis of duck and human isolates provided no evidence for reassortment. Our findings support the concept that intermingling of humans, pigs and ducks on Chinese farms is favourable to the generation of new, potentially hazardous strains of influenza virus.

(Accepted January 18 1996)

Correspondence:

c1 Corresponding author.

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