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H5N1 virus

Transmission studies resume for avian flu

In January 2012, influenza virus researchers from around the world announced a voluntary pause of 60 days on any research involving highly pathogenic avian influenza H5N1 viruses leading to the generation of viruses that are more transmissible in mammals1. We declared a pause to this important research to provide time to explain the public-health benefits of this work, to describe the measures in place to minimize possible risks, and to enable organizations and governments around the world to review their policies (for example, on biosafety, biosecurity, oversight and communication) regarding these experiments.

During the past year, the benefits of this important research have been explained clearly in publications2,3,4,5,6,7 and meetings8,9,10. Measures to mitigate the possible risks of the work have been detailed11,12,13. The World Health Organization has released recommendations on laboratory biosafety for those conducting this research14, and relevant authorities in several countries have reviewed the biosafety, biosecurity and funding conditions under which further research would be conducted on the laboratory-modified H5N1 viruses10,15,16,17. Thus, acknowledging that the aims of the voluntary moratorium have been met in some countries and are close to being met in others, we declare an end to the voluntary moratorium on avian-flu transmission studies.

The controversy surrounding H5N1 virus-transmission research has highlighted the need for a global approach to dealing with dual-use research of concern. Developing comprehensive solutions to resolve all the issues will take time. Meanwhile, H5N1 viruses continue to evolve in nature.

Because H5N1 virus-transmission studies are essential for pandemic preparedness and understanding the adaptation of influenza viruses to mammals, researchers who have approval from their governments and institutions to conduct this research safely, under appropriate biosafety and biosecurity conditions, have a public-health responsibility to resume this important work. Scientists should not restart their work in countries where, as yet, no decision has been reached on the conditions for H5N1 virus transmission research. At this time, this includes the United States and US-funded research conducted in other countries. Scientists should never conduct this type of research without the appropriate facilities, oversight and all necessary approvals.

We consider biosafety level 3 conditions with the considerable enhancements (BSL-3+) as outlined in the referenced publications11,12,13 to be appropriate for this type of work, but recognize that some countries may require BSL-4 conditions in accordance with applicable standards (such as Canada). We fully acknowledge that this research — as with any work on infectious agents — is not without risks. However, because the risk exists in nature that an H5N1 virus capable of transmission in mammals may emerge, the benefits of this work outweigh the risks.


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Correspondence to Yoshihiro Kawaoka.

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Fouchier, R., García-Sastre, A., Kawaoka, Y. et al. Transmission studies resume for avian flu. Nature 493, 609 (2013).

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