Reply to “Studies on Influenza Virus Transmission between Ferrets: the Public Health Risks Revisited”

Lipsitch, Marc; Inglesby, Thomas V.

Fouchier repeatedly describes his adjustments to the probability estimates we proposed as "conservative," implying that the actual risk is even less than his figures show. His analysis is not conservative. His estimate of one LAI per~700,000 worker-years is dramatically lower than that currently estimated for any category of laboratory, and current estimates themselves are too low due to underreporting (9) . Moreover, describing the estimates as conservative is at odds with the use of large factors to stand for unknown effects of safety enhancements, inconsistent use of numerators and denominators to favor lower probabilities, and the assumption that safety enhancements used in the Erasmus MC laboratory will be effective in the face of evidence that many laboratory infections have no traceable cause and that many mishaps involving infectious exposures may occur outside the "home laboratory." The assumptions of antiviral and vaccine effectiveness and reduced human transmissibility and virulence of selected strains range from uncertain (in the case of much of the published work) to unknowable (in the case of experiments not yet done) and false (in the case of reduced virulence and vaccine availability in examples such as H7N1) (15) . Such assumptions are "anticonservative," giving too-optimistic predictions. Further problems include unsupported claims that the implementation of the select agent program necessarily strengthens biosafety. For example, in the CDC report on the lab accident involving H5N1, the description of the event indicates that scientists were making their decisions in reference to the select agent rule, as opposed to whether there was a biosafety breach (41) . The quality of "targeted risk assessments" undertaken before each study is performed is unclear; such assessments have not been quantitative to date (42, 43) .