The World Health Organization (W.H.O.) warned on Monday that a recent case of monkeypox confirmed in a person who traveled from Nigeria to the U.K. in recent days indicates that there is a “risk of ongoing transmission” of the virus in the West African nation, Nigeria’s Vanguard newspaper reported on Tuesday.

Vanguard quoted a May 16 report by the W.H.O. which stated the following:

On 7 May 2022, WHO was informed of a confirmed case of monkeypox in an individual who travelled from the United Kingdom to Nigeria and subsequently returned to the United Kingdom. The case developed a rash on 29 April 2022 and arrived in the United Kingdom on 4 May, departing Nigeria on 3 May.

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Since the case was immediately isolated and contact tracing was performed, the risk of onward transmission related to this case in the United Kingdom is minimal. However, as the source of infection in Nigeria is not known, there remains a risk of ongoing transmission in this country.

The monkeypox patient in question traveled through the Nigerian states of Lagos and Delta during his or her recent visit to the country, which is located in West Africa. Monkeypox is considered endemic in Nigeria’s Delta state. The W.H.O., which is the U.N.’s international public health body, confirmed on May 16 that the patient tested positive for the “West African clade” of monkeypox, which has a lower fatality rate (about one percent) than its Central African counterpart (as high as ten percent).

The W.H.O.’s website reveals that humans may transmit monkeypox, which is a viral zoonotic disease, by coming into contact with “live and dead animals through hunting and consumption of wild game or bush meat.” The public health organization notes that, while the animal reservoir for monkeypox remains unknown, scientists suspect it is “likely to be among rodents.” Other animal reservoirs of the disease include non-human primates.

The U.S. Centers for Disease Control and Prevention (CDC)’s website reveals details of the virus’s origin, stating:

Monkeypox was first discovered in 1958 when two outbreaks of a pox-like disease occurred in colonies of monkeys kept for research, hence the name ‘monkeypox.’ The first human case of monkeypox was recorded in 1970 in the Democratic Republic of Congo during a period of intensified effort to eliminate smallpox. Since then monkeypox has been reported in humans in other central and western African countries.

“Monkeypox begins with fever, headache, muscle aches, and exhaustion. … The incubation period (time from infection to symptoms) for monkeypox is usually 7−14 days but can range from 5−21 days,” according to the CDC.

The disease causes patients to develop a rash with distinctive lesions that may number from a few to several thousand, depending on the case’s severity.

The W.H.O., in an updated bulletin published on May 18, said it had detected six additional cases of monkeypox in the U.K., along with one suspected case of the disease. The health body had yet to determine the precise origin of the new infections at press time on May 18 and did not say if they were linked to the cases confirmed on May 7 in the individual who had recently traveled from the U.K. to Nigeria and back. The organization provided the following details about the emerging caseload:

On 13 May 2022, WHO was notified of two laboratory confirmed cases and one probable case of monkeypox, from the same household, in the United Kingdom. On 15 May, four additional laboratory confirmed cases have been reported amongst Sexual Health Services attendees presenting with a vesicular rash illness and in gay, bisexual, and other men who have sex with men.

The W.H.O.’s website acknowledges that “while close physical contact is a well-known risk factor for transmission, it is unclear at this time if monkeypox can be transmitted specifically through sexual transmission routes. Studies are needed to better understand this risk.”