Hugo López-Gatell, who leads Mexico’s coronavirus response, knows firsthand the costs of travel bans. One Saturday afternoon in 2009, he got a query from the Pan American Health Organization about news reports of an unusual flu outbreak in the state of Veracruz. López-Gatell, then chief epidemiologist at the Mexican Health Ministry, gathered all the available data and sent back a report the next evening. It turned out to be the start of the H1N1 flu pandemic. Mexico was “absolutely, proudly, compulsively transparent,” he recalled.