Infonaut's Hospital Watch Live system uses a combination of tracking software and inexpensive radio-frequency ID tags to record the location of anything that could possibly transport microbes, including the doctors and nurses themselves. Wireless receivers throughout the building transmit the position of each tag to a central computer about every three seconds. When staff members identify a patient infected with hospital-borne bacteria, such as MRSA, they enter that patient's data into the system, and it retraces which rooms he has visited and what equipment and people he has been in contact with. It then IDs and ranks other potential disease carriers and demarcates hot zones throughout the building—high-traffic areas that could be reservoirs of disease. Janitorial staff can then concentrate their efforts on those zones, rather than wasting precious time scrubbing clean rooms.