Avian Influenza A (H5N1) Virus Antibodies in Poultry Cullers, South Korea, 2003–2004

Donghyok Kwon, Joo-Yeon Lee, Wooyoung Choi, Jang-Hoon Choi, Yoon-Seok Chung, Nam-Joo Lee, Hyang-Min Cheong, Jacqueline M. Katz, Hee-Bok Oh, Haewol Cho, and Chun Kang

Author affiliations: Korea Centers for Disease Control and Prevention, Osong, South Korea (D. Kwon, J.-Y. Lee, W. Choi, J.-H. Choi, Y.-S. Chung, N.-J. Lee, H.-M. Cheong, H.-B. Oh, H. Cho, C. Kang); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (J.M. Katz)

Abstract

Transmission of influenza (H5N1) virus from birds to humans is a serious public health threat. In South Korea, serologic investigation among 2,512 poultry workers exposed during December 2003–March 2004 to poultry with confirmed or suspected influenza (H5N1) virus infection found antibodies in 9. Frequency of bird-to-human transmission was low.

The highly pathogenic avian influenza (H5N1) virus has posed a serious public health threat since 1997, when the first transmission of the virus from birds to humans was reported in Hong Kong (1,2). In South Korea, during December 2003–March 2004, this virus caused 19 outbreaks in 7 provinces (10 outbreaks on chicken farms and 9 on duck farms), which prompted a massive mobilization to cull birds and contain the outbreak (3). Vaccination of poultry against influenza (H5N1) virus was legally prohibited, and a stamping out policy was considered as a control option. Culling of ≈5 million birds was conducted on all farms with infected poultry and all poultry farms within a 3 km–radius protection zone.

All persons who participated in the culling operations were equipped with World Health Organization (WHO)–recommended personal protective equipment (PPE) (4). To prevent the possibility of mixed infection with human and avian influenza viruses, previously nonvaccinated participants were vaccinated with a seasonal influenza vaccine and given oseltamivir as an additional prophylactic measure.

During the outbreaks, 142 respiratory specimens were collected from persons who had influenza-like illness and tested by reverse transcription PCR selective for the matrix and hemagglutinin (H) 5 genes and by virus isolation in cell culture; however, no influenza (H5N1) virus was detected (Korea Centers for Disease Control and Prevention [CDC], unpub. data).

The definition of a case of influenza-like illness was sudden onset of fever (>38°C) with cough or sore throat. According to previous serosurveys and outbreak investigations, influenza (H5N1) virus is poorly transmitted from birds to humans (5–8). To trace the frequency of transmission of the influenza (H5N1) virus to persons who had been exposed to the confirmed or suspected virus-infected poultry, a serosurvey was conducted by the Korea CDC.