The two new infections involve people from the same family, but are not related to the previous case, according to the UK Health Security Agency (UKHSA). One is in hospital for treatment and the other is in isolation.
The first patient was a person who had recently visited Nigeria. It is suspected that the person was infected there before returning to the UK.
Read also. Rare monkeypox infection appears in England
The very rare virus, from which most people recover after a few weeks, was first identified in the UK in 2018. Since then, there have been few confirmed cases. It usually occurs in remote areas of Central and West Africa, near tropical rainforests.
British health authorities maintain that monkeypox is not easily transmitted between humans and that the risk to the general public is very low.