The UKHSA has not disclosed exact areas where infections have emerged but did confirm the disease has achieved community transmission.
Unlike Covid, monkeypox can only travel via close contact, including partners and people living in the same home.
Officials expect the case totals to continue increasing globally, with US President Joe Biden dubbing the outbreak a “concern”.
Dr Susan Hopkins, the UKHSA Chief Medical Adviser, told people to “be aware” in a warning today.