A new analysis of smartphone data, conducted at ProPublica’s request, shows how interconnected the country is with visitors to Las Vegas — which heightens concerns about the limitations of interstate contact tracing. The companies X-Mode and Tectonix analyzed travel to and from Las Vegas during four days, a Friday to Monday, in mid-July. In compliance with privacy laws, X-Mode collects data from smartphone users, mainly those using fitness and weather apps that track their location. The data represents about 5% of the smartphone users in the United States. Tectonix analyzed the data and visualized it on a map.
During the four-day period, about 26,000 devices were identified on the Las Vegas Strip. Some of those same smartphones also showed up in every state on the mainland except Maine in those same four days. About 3,700 of the devices were spotted in Southern California in the same four days; about 2,700 in Arizona, with 740 in Phoenix; around 1,000 in Texas; more than 800 in Milwaukee, Detroit, Chicago and Cleveland; and more than 100 in the New York area.
The cellphone analysis highlights a reason the virus keeps spreading, said Oscar Alleyne, an epidemiologist and chief program officer with the National Association of County and City Health Officials. “People have been highly mobile, and as a result, it makes sense why we see the continuation of the surge.”