Four-fifths of the people in England who have been infected with monkeypox live in London, an investigation by the UK Health Security Agency has found.
Of the cases interviewed, 99% of those infected are men and their average age is 38, the agency added after analysing 336 of the 366 confirmed cases found in the UK since the outbreak began last month.
The same overwhelming majority of cases – 99% – involve men who are gay, bisexual or have sex with other men, the UKHSA said. Interviews it has conducted with 45 men with monkeypox specifically about their sexual health found that 44% had visited “sex-on-premises venues” in the UK or abroad, such as saunas, sex clubs and dark rooms, while they were incubating the infection.
In addition, 64% had met new sexual partners during their incubation period through a dating app. Incubation lasts anywhere between five and 21 days.
Tracing all the sexual partners of men who have contracted monkeypox will be hard, the UKHSA admitted, as “most cases reported having sexual contact with new or casual partners … where contact details were unavailable for tracing”.
The UKHSA report is based on close scrutiny of the history of the 336 laboratory-confirmed cases that had been identified in the UK by 8 June, including detailed questionnaires that 152 cases filled in. That total rose to 366 on Friday.
“A high proportion of England cases were known to be London residents”, it said, adding that 224 of 276 people for whom they had a home address lived in the capital.
In terms of their sex, 311 of 314 confirmed cases were men, with three women. They ranged in age from 32 to 44.
“Findings show that monkeypox is being transmitted in geographically diffuse sexual networks”, the report added. Among the 45 interviewed 98% had had sex with other men during the incubation period. In that group 60% had been diagnosed with a sexually transmitted infection during the previous year, 44% had had more than ten sexual partners in the preceding three months and the same proportion had taken part in group sex while the infection was incubating.
“Sexual networks involved in this outbreak are interconnected both within and without the UK”, the UKHSA said. Among the 45 cases, 30% had had sex in a city outside their usual place of residence, 20% had taken part in sexual activity abroad and 24% had had sex with men who were not UK residents.
Health officials hope that sex-on-premises venues will agree to implement “targeted interventions [which] would support outbreak control”, to try to reduce the risk of further transmission of the monkeypox virus.
The agency’s “early evidence and preliminary analyses” also say that the number of detected cases so far means that the outbreak in England is at level 2 of four levels. That is defined as “transmission within a defined sub-population with high numbers of close contacts”.
However, with numbers rising, officials are monitoring it for signs that it has reached level 3 – “transmission within multiple sub-populations or larger sub-population”.
