Studies on Influenza Virus Transmission between Ferrets: the Public Health Risks Revisited

Fouchier, Ron A. M.

The biosafety conditions in the Erasmus MC facility thus extend well beyond "normal" BSL3 conditions for working with viruses, and a number of these biosafety measures should be considered when the probability of LAIs is inferred from the U.S. CDC report. Unfortunately, an exact number for the effectiveness of individual biosafety measures is not available (9) . However, it is reasonable to assume that the effectiveness of the physical separation of personnel from the viruses they work with through the use of class 3 isolator units and class 3 biosafety cabinets, the use of personnel protective equipment, the extensive training program, the use of experienced personnel only, and the application of a two-person rule to reduce human error during animal experiments would yield a decrease in the probability of LAIs. Although the magnitude of this increase in safety is not known, I assume that it is at least a factor of 10. Using the risk analysis done by others and this assumption of reduced risk, the probability of a LAI in the Erasmus MC facility would be reduced to below 0.1 ϫ (1.4 ϫ 10 Ϫ5 ), or Ͻ1.4 ϫ 10 Ϫ6 per person-year. The quantitative risk assessment to be performed upon request of the U.S. government (17) will have the challenging task of a better quantitative assessment of the effectiveness for each of the biosafety measures in individual laboratories, to yield exact numbers instead of the conservative estimates used here.