Sexual transmission at two festivals in Europe may have sparked the world’s escalating monkeypox outbreak, a World Health Organization expert has claimed.

Dr David Heymann, who used to head the WHO’s emergencies department, revealed it was the leading theory behind the origins of the current cluster of cases.

He said: ‘We know monkeypox can spread when there is close contact with the lesions of someone who is infected, and it looks like sexual contact has now amplified that transmission.