The requested budget will be used to replace the current outdated housing system for biosafety risk 3 pathogen-infected mice by two new individual systems. Thus, the outdated housing system, which will likely encounter operating errors in the near future, can be replaced, while the current capacity can be increased. As such, multiple laboratories can work on new therapies or vaccines against virulent pathogens including hepatitis C, D, and E virus, and HIV. Both racks contain 59 individually vented cages with hermetic seals and operate at an under pressure to avoid contamination of the environment and infection of people. We request two cages not only to increase the capacity, but also to have a back-up rack in case of operating errors or maintenance cleaning. In this way, we do not have to abort important experiments. Ultimately, all of this benefits science, but also safety and animal welfare.