Balancing safety, risk in the debate over the new H5N1 viruses

agent and must be worked with under BSL-3 with enhancements. The BSL-3 designation is given to pathogens that can be transmitted through the air and can cause serious or fatal disease but for which treatment exists. Most facilities in the United States with infectious disease research programs have BSL-3 laboratories.

In addition, many hospitals have areas that can be operated at this level; these areas are used for isolating patients with highly contagious diseases. In contrast, BSL-4 is reserved for pathogens for which there is no known treatment and BSL-4 laboratory requirements are such that there are only four working BSL-4 laboratories in the United States.

Adolfo García-Sastre of the Mount Sinai School of Medicine argues that the H5N1 viruses in question may well be less pathogenic than they were before passage through ferrets, but they could still be quite dangerous, so preventing human exposure is crucial. He says, however, that the ultimate level of biosecurity, BSL-4, is excessive in this case and would stifle the pace of discovery. There are both therapeutics and vaccines available for H5N1, says García-Sastre, so he advocates for conducting the research in enhanced BSL-3 facilities, which he says offer the necessary security measures, including interlocked rooms with negative pressure, HEPA-filtered air circulation, and appropriate decontamination and/or sterilization practices for material leaving the facility.

Michael Imperiale and Michael Hanna of the University of Michigan, on the other hand, make their case that the H5N1 viruses merit BSL-4 containment. Although H5N1 that cannot be transmitted from human to human would normally be handled in a BSL-3 facility, researchers changed the virus’s biosafety profile when they enhanced its ability to transmit between mammals. According to Imperiale and Hanna, the vaccine for H5N1 is not widely available, and drug resistance and a slow distribution system for antiviral drugs mean a small outbreak could never be contained.

Since the controversy began in December, H5N1 viruses and flu research continue to be the source of much debate. The release says that “mBio and the American Society for Microbiology present these commentaries as a means of fostering a discussion and eventually achieving consensus about H5N1 biosecurity that is based on the scientific facts surrounding the subject.”

— Read more in Adolfo García-Sastre, “Working Safely with H5N1 Viruses,” mBio 3, no. 2 (6 march 2012):e00049-12 (doi:10.1128/00049-12); Michael J. Imperialea and Michael G. Hanna III, “Biosafety Considerations of Mammalian-Transmissible H5N1 Influenza,” mBio 3, no. 2 (6 March 2012):e00043-12 (doi:10.1128/mBio.00043-12); Arturo Casadevall and Thomas Shenk, “Mammalian-Transmissible H5N1 Virus: Containment Level and Case Fatality Ratio,” mBio 3, no. 2 (6 March 2012)