China's new maximum biosafety level-4 (BSL-4) laboratories plan to perfect containment practices by starting work with the virus responsible for Crimean–Congo haemorrhagic fever (CCHF), which requires only BSL-3 containment under Chinese regulations (Nature 542, 399–400; 2017). US researchers, however, must use a BSL-4 facility for culturing and handling this deadly pathogen. Is the United States overestimating the potential biohazard of CCHF, or is China underestimating it?

It seems that countries without endemic CCHF, such as the United States and the United Kingdom, err on the side of caution by requiring BSL-4, whereas those such as China that experience CCHF outbreaks seem more amenable to allowing less stringent containment of the virus (M. Weidmann et al. J. Gen. Virol. 97, 2799–2808; 2016). This illustrates how different conclusions of expert biological-risk assessors result in differing biosafety practices.

And in countries such as Uzbekistan, where CCHF outbreaks occur, but which have no BSL-4 or BSL-3 facilities, and which forbid the export of pathogen samples even for diagnosis, clinicians and researchers are forced to make do as best they can.