Addressing the medical issues of homeless people is the health equity challenge of our time. The most recent US Department of Housing and Urban Development (HUD) report on homelessness, published in 2015, estimated that about 564 000 homeless people in the United States live in shelters and on the streets. This figure, based on a point-in-time snapshot on a single night each January, may well be an underestimate, given varying definitions of homelessness, peripatetic populations, and the lack of robust surveillance systems.