A health worker gives information on the prevention of COVID-19 outside a wholesale food market in Mexico City, Mexico, on June 18, 2020. (Photo by Francisco Canedo/Xinhua)

A vendor wearing a face mask waits for customers at a wholesale food market amid the COVID-19 outbreak in Mexico City, Mexico, on June 18, 2020. (Photo by Francisco Canedo/Xinhua)

A customer wearing a face mask is seen at a wholesale food market amid the COVID-19 outbreak in Mexico City, Mexico, on June 18, 2020. (Photo by Francisco Canedo/Xinhua)

Customers wearing face masks shop at a wholesale food market amid the COVID-19 outbreak in Mexico City, Mexico, on June 18, 2020. (Photo by Francisco Canedo/Xinhua)

Health workers wait for customers to check their temperatures at a wholesale food market amid the COVID-19 outbreak in Mexico City, Mexico, on June 18, 2020. (Photo by Francisco Canedo/Xinhua)

A customer has his temperature checked at a wholesale food market amid the COVID-19 outbreak in Mexico City, Mexico, on June 18, 2020. (Photo by Francisco Canedo/Xinhua)