The US Centre for Disease Control and Prevention (CDC) on Friday confirmed that a rare case of human monkeypox was detected in Texas, making it the first case of the virus seen in the state.
The viral illness was found in a U.S. resident, who recently travelled from Nigeria to the US and is currently hospitalised in Dallas.
He is in stable condition, according to the health department's statement.
"While rare, this case is not a reason for alarm and we do not expect any threat to the general public," Dallas County Judge Clay Jenkins said.
Other than Nigeria, outbreaks have also been reported in Central and West African countries since 1970, with a large outbreak in people in the US in 2003, according to the CDC.
Monkeypox, which belongs to the same family of viruses as smallpox, is a rare but potentially serious viral illness.
It typically begins with flu-like symptoms and swelling of the lymph nodes and gradually develops to widespread rashes on the face and body.
It can spread from person to person through respiratory droplets.
The CDC said since travellers were wearing masks due to COVID-19, the risk of spread of monkeypox via respiratory droplets to others on air planes and at the airports was low.
The patient was infected with the strain most commonly found in parts of West Africa, including Nigeria, CDC added.
The CDC said it was working with local health officials to contact airline passengers and others who were in contact with the infected traveller during their flights from Lagos to Atlanta on July 8 and from Atlanta to Dallas on July 9.
The last time monkeypox was seen in the U.S. was in 2003.
Nearly 50 people fell ill after imported African rodents infected prairie dogs, which subsequently infected humans, the CDC said.
This launched a government search across 15 states for infected prairie dogs.