The monkeypox outbreak in Western countries is “almost entirely” driven by sexual transmission, raising the spectre of stigma and discrimination, says a leading epidemiologist and public health physician.

Professor Andrew Grulich — head of the HIV epidemiology and prevention program at the Kirby Institute, UNSW Sydney — says transmission trends to mid-August show 97-99% of monkeypox cases in the UK and the US have occurred among men who have sex with men.

And about a third of cases in the UK and Europe have also been HIV positive.

“I would say that this remarkable and stable concentration in highly sexually active gay, bisexual and other men who have sex with men does suggest — more than suggests, it demonstrates — sexual transmission,” he told a seminar last week.