Human To Human Transmission Of Bird Flu

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Main Category: Bird Flu / Avian Flu
Also Included In: Flu / Cold / SARS;  Infectious Diseases / Bacteria / Viruses;  Immune System / Vaccines
Article Date: 08 Apr 2008 - 8:00 PDT

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Tests indicate that a father diagnosed with bird flu in China probably caught the disease from his son, only increasing concern about transmission of the virus between humans. This was published early online and in the April 2008 issue of The Lancet.

As of April 2, 2008, there have been 376 cases of infection with the highly pathogenic avian influenza A (H5N1) virus with 238 deaths reported in 14 different countries since November 2003. While most cases have been scattered, about one quarter of all cases have been in clusters of two or more people.

These two men, diagnosed within a week of one another, were investigated by Professor Yu Wang, Chinese Centre for Disease Control and Prevention, Beijing, China, and colleagues in December 2007 in China's Jiangsu Province. Both laboratory and field tests were performed immediately to determine a positive H5N1 infection in both cases. Additionally, 91 people with whom they had come into close exposure, and more removed contacts who became at all ill were tested.

The son, aged 24, died, while his 52 year old father survived after receiving early antiviral treatment and post-vaccination plasma from a participant in an H5N1 vaccine trial. The only potential point of exposure of the son's was a visit to a poultry market six days before the illness's onset. In the meanwhile, the father had considerable unprotected exposure to his sick son.

All 91 exposed contacts gave consent for examination -- of these, 78 were administered anti-retroviral prophylaxis and two suffered from mild illness. However, all 91 tested negative for H5N1. The viruses isolated from father and son were genetically identical with the exception of one small base change in the nucleic acid chain making up the H5N1 genetic structure.

The authors conclude that the transmission was probably between the two men. "Limited, non-sustained person-to-person transmission of H5N1 virus probably occurred in this family cluster...Viral characteristics required for sustained person-to-person transmission remain unknown. H5N1 clusters require urgent investigation because of the possibility that a change in the epidemiology of H5N1 cases could indicate that H5N1 viruses have acquired the ability to spread more easily among people."

Dr Jeremy Farrar, Hospital for Tropical Diseases, Ho Chi minh City, Vietnam, and colleagues, wrote an accompanying comment, in which they say: "Whatever the underlying determinants, if we continue to experience widespread, uncontrolled outbreaks of H5N1 in poultry, the appearance of strains well adapted to human beings might just be matter of time. In the meantime, all family contacts of a patient with probable or confirmed H5N1 should be given chemoprophylaxis and placed under surveillance. Personal protection and advice must be extended to the family members and health workers visiting and looking after patients in hospital."

"Today's study is a superb piece of work showing the benefit of a longstanding and trusting international collaboration that began during the severe acute respiratory syndrome epidemic. Such collaborations sustained over several years, centred in affected countries, and closely linked with WHO are our best chance of combating current and future threats to international health and ensuring that benefits are shared worldwide."

Probable limited person-to-person transmission of highly pathogenic avian influenza A (H5N1) virus in China
Hua Wang, Zijian Feng, Yuelong Shu, Hongjie Yu, Lei Zhou, Rongqiang Zu, Yang Huai, Jie Dong, Changjun Bao, Leying Wen, Hong Wang, Peng Yang, Wei Zhao, Libo Dong, Minghao Zhou, Qiaohong Liao, Haitao Yang, Min Wang, Xiaojun Lu, Zhiyang Shi, Wei Wang, Ling Gu, Fengcai Zhu, Qun Li, Weidong Yin, Weizhong Yang, Dexin Li, Timothy M Uyeki, Yu Wang
The Lancet, April 8, 2008
DOI:10.1016/S0140-6736(08)60493-6
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Person-to-person transmission of influenza A (H5N1)
Nguyen Tran Hien, Jeremy Farrar, Peter Horby
The Lancet, April 8, 2008
DOI:10.1016/S0140-6736(08)60494-8
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Written by Anna Sophia McKenney
Copyright: Medical News Today
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