Monkeypox in the UK, apparently from Nigeria: extensive contact tracing in Britain
On May 7, 2022, WHO was notified of a confirmed case of monkeypox in a person who traveled from the UK to Nigeria. The case developed a rash on April 29, 2022 and returned to the UK on May 4. Monkeypox was suspected and the case was immediately isolated.
Since May 11, extensive contact tracing has been undertaken to identify exposed contacts in healthcare facilities, community and international flight. These people are followed for 21 days from the date of the last exposure to the case. None have reported compatible symptoms so far.
As the case was immediately isolated and contact tracing was carried out, the risk of onward transmission from this case in the UK is minimal. However, as the source of infection in Nigeria is not known, there remains a risk of continued transmission in that country.
Monkeypox is a sylvatic zoonosis with accidental human infections that usually occur sporadically in forested regions of central and western Africa. It is caused by the monkeypox virus which belongs to the orthopoxvirus family. Monkeypox can be transmitted by contact and by droplet exposure via large exhaled droplets. The incubation period for monkeypox is usually 6 to 13 days but can range from 5 to 21 days. The disease is often self-limiting and symptoms usually resolve on their own within 14 to 21 days. Symptoms can be mild or severe, and lesions can be very itchy or painful. The animal reservoir remains unknown, although it is probably among rodents. Contact with live and dead animals through hunting and consumption of wild game or bushmeat are known risk factors.
There are two clades of monkeypox virus, the West African clade and the Congo Basin (Central Africa) clade. Although the West African clade of monkeypox virus infection sometimes causes severe disease in some individuals, the disease is usually self-limiting. The case fatality rate for the West African clade has been documented to be around 1%, while for the Congo Basin clade it can be as high as 10%. Children are also at higher risk, and monkeypox during pregnancy can lead to complications, congenital monkeypox, or stillbirth.
Less severe cases of monkeypox may go undetected and pose a risk of human-to-human transmission. Those traveling and exposed are likely to have low immunity to infection, as the endemic disease is geographically restricted to parts of West and Central Africa. While a vaccine has been approved for the prevention of monkeypox and the traditional smallpox vaccine also offers protection, these vaccines are not widely available and populations around the world under the age of 40 or 50 no longer benefit from the protection offered by previous smallpox vaccination programs.
Public health response
• UK health authorities have set up an incident management team to coordinate the identification and management of contacts.
• Since May 11, extensive contact tracing has identified exposed contacts in the community, healthcare setting and on the international flight. None have reported compatible symptoms so far.
• All identified contacts have been assessed and classified according to their exposure to the case and are followed up accordingly by active or passive surveillance for 21 days after their last exposure to the case. Post-exposure prophylaxis with vaccination is offered to high-risk contacts.
• Nigerian authorities were notified of this case and travel history to Nigeria on 7 May. The case reported no contact with anyone with known rash or monkeypox in Nigeria. Details of trips and contacts in Nigeria have been shared with Nigerian authorities for follow-up if necessary.
In the UK, seven cases of monkeypox have already been reported; all imports were linked to travel history to or from Nigeria. In 2021, two separate cases of human monkeypox imported from Nigeria were also reported by the United States of America.
As of September 2017, Nigeria continues to report cases of monkeypox. From September 2017 to April 30, 2022, a total of 558 suspected cases were reported in 32 states across the country.