Health officials are acting to keep the bacterium that causes plague - the "black death" of the 14th century - from hitching a ride to the USA.
Fatal outbreaks have been reported in India.
Air travelers from India to Honolulu, Los Angeles, San Francisco, Miami, Seattle, New York and Chicago are getting "plague alert" notices.
They advise travelers to see a doctor if they develop symptoms within seven days: high fever, nausea and vomiting.
"The risk . . . is very small," says epidemiologist David Dennis of the Centers for Disease Control and Prevention in Fort Collins, Colo.
"But it certainly merits . . . a very active surveillance and information system," he says.
Pneumonic plague, the more deadly form that infects the lungs and can be transmitted by coughing, has been reported in New Delhi and Calcutta as well as Surat, where 400,000 people fled last week.
The Indian Embassy reports 41 deaths in Surat; news reports put the number higher.
In Maharashtra, the embassy says, almost 100 non-fatal cases of the flea-borne bubonic plague have occurred.
Antibiotics and insecticides have been sent to both regions.
A number of countries are considering steps to monitor travel to and from India.
But the World Health Organization is advising against travel restrictions at this time.
Dennis says international airline flight crews are required to report any ill passenger to U.S. quarantine authorities before landing.
