William T. Salmeron, the chief of Emergency Medical Services for the city, told his colleagues that workers should take “routine exposure control precautions” as they would in dealing with any respiratory illness. Those included getting the travel history of anyone with symptoms, giving patients surgical masks, and moving up to gloves, gown, protective eyewear and an N95 mask “if travel history risk factors warrant.”

“At this time the potential risk of infection in the US is LOW,” he wrote.

Collin M. Arnold, director of the city’s homeland security office, sent an email to Dr. Avegno and other city officials on Jan. 27, suggesting they “should probably get together and discuss public safety concerns during Mardi Gras and on the parade route.”

The New Orleans Police Department, he said, had been asking about personal protective equipment “and general concerns (they shake a lot of hands and come in contact with a lot of people on the route every day).” He suggested putting together a “guide sheet for all responders” that would offer them “common sense mitigation tasks.”

That same day, Tyrell Morris, the executive director of the city’s 911 service, told city officials about a questionnaire and worksheet that the International Academies of Emergency Dispatch was suggesting they use for all suspected coronavirus patients.

Dr. Emily Nichols, the medical director for the city’s emergency medical services, suggested they add a question asking suspected carriers whether they had been within six feet of another person thought to be infected with the virus.