The Nosoi commute : a spatial perspective on the rise of BSL-4 laboratories in cities
Recent H5N1 influenza research has revived the debate on the storage and manipulation of 
potentially harmful pathogens. In the last two decades, new high biosafety (BSL-4) laboratories 
entered into operation, raising strong concerns from the public. The probability of an accidental 
release of a pathogen from a BSL-4 laboratory is extremely low, but the corresponding risk -- defined 
as the probability of occurrence multiplied by its impact -- could be significant depending on the 
pathogen specificities and the population potentially affected. A list of BSL-4 laboratories throughout 
the world, with their location and date of first activity, was established from publicly available 
sources. This database was used to estimate the total population living within a daily commuting 
distance of BSL-4 laboratories, and to quantify how this figure changed over time. We show that 
from 1990 to present, the population living within the commuting belt of BSL-4 laboratories 
increased by a factor of 4 to reach up to 1.8% of the world population, owing to an increase in the 
number of facilities and their installation in cities. Europe is currently hosting the largest population 
living in the direct vicinity of BSL-4 laboratories, while the recent building of new facilities in Asia 
suggests that an important increase of the population living close to BSL-4 laboratories will be 
observed in the next decades. We discuss the potential implications in term of global risk, and call for 
better pathogen-specific quantitative assessment of the risk of outbreaks resulting from the 
accidental release of potentially pandemic pathogens.