United States health officials have said that over 200 people in no fewer than 27 states in the US are being tracked over the possibility of uncommon monkeypox infections.
The fear is that those people may have come in contact with a Texas resident who brought the disease from Nigeria this month.
The Texas resident – discovered as the first monkeypox case in the country since 2003 – was taken to hospital and he is in a stable condition.
No new cases have been found so far.
The Centers for Disease Control and Prevention (CDC) revealed it was concerned about passengers who boarded the two flights that the man made may have been exposed to the rare disease.
The CDC said the man flew into Atlanta, Georgia from Nigeria on July 9 before boarding a flight to Dallas, where he was taken to the hospital.
It said it was liaising with the airlines to assess “potential risks to those who may have had close contact with the traveller”.
However, the chances that the disease would spread on the plane were low as passengers wore face masks, it added.
A CDC spokesperson who talked to the BBC said it was “working with state and local health departments to follow up with individuals who may have been exposed to monkeypox”.
“The risk to the general public is thought to be low,” the spokesperson said, adding that none of the 200 people they were monitoring were thought to be “high risk”.
Monkeypox is an uncommon viral disease from the family of smallpox, but it is not as severe as smallpox.
It is prevalent in remote parts of central and west African countries that are situated near tropical rainforests.