No such cases have emerged in the United States, but international travel means unvaccinated people might bring the illness back home after visiting an endemic area.
The yellow fever outbreak comes as the Zika virus continues to affect countries throughout the Americas.
However, "early recognition may be difficult in countries such as the United States, where most physicians have never seen a case of yellow fever," the authors pointed out.
Early symptoms include a fever that can mimic flu, followed by a period of remission, and then a stage called "intoxication" -- high fever, liver dysfunction and jaundice, and even kidney failure, heart and nervous system dysfunction, and shock.
As he climbs out of his car and walks across to the entrance of Bakassi camp for internally displaced persons in Borno, northern Nigeria, Dr Terna Nomwhange is met by a familiar sight.
Standing at the gates, greeting a tired, dusty family laden with possessions, is a team of polio vaccinators.
More than eight million people are being targeted with yellow fever vaccines in the states of Borno, Zamfara Kwara and Kogi states in 2018.
By providing both polio and yellow fever vaccinations, the polio infrastructure protects everyone – the young children vulnerable to polio, as well as the whole population at risk of yellow fever.
"The outbreak is affecting areas in close proximity to major urban centers [in Brazil] where yellow fever vaccine is not routinely administered," Fauci and Paules warned.
The authors stressed that there's no evidence yet that mosquitoes are transmitting yellow fever between infected people.