Mexico faces mid-term elections for Congress in the fall, and President Felipe Calderón’s National Action Party is trailing slightly in the polls over its main rivals, who would like nothing better than to see a health emergency translate into a political defeat. In the face of a public health system that seemed incapable of diagnosing and treating the outbreak quickly, the government felt it had little choice but to shut down Mexico City, dealing a severe blow to an already crippled economy.