Contact tracing in the US has been hampered by the lack of a single national app, with 10 states and DC creating their own and most having no app at all (David Uberti/Wall Street Journal)

David Uberti / Wall Street Journal:
Contact tracing in the US has been hampered by the lack of a single national app, with 10 states and DC creating their own and most having no app at all  —  The lack of a national plan on contact tracing has resulted in a state-by-state patchwork of differing technological tools