UK mpox outbreak of 2022: Where cases started and how infection spread to 3,000 people

Transmission of mpox – monkeypox – in the UK was linked to sexual activity and hit more than 3,000 by December 2022

Children at risk as mpox variant hits Congo displacement camps (Reuters)

The World Health Organization has declared outbreaks of a new form of mpox in Congo and other parts of Africa a global emergency, with cases confirmed among children and adults in more than a dozen countries.

Earlier this week, the Africa Centers for Disease Control and Prevention announced that the mpox, formerly monkeypox, outbreaks were a public health emergency, with more than 500 deaths, and called for international help to stop the spread of the virus.

The declaration comes following the emergence of a new strain, Clade 1b. Currently, there are no cases of Clade 1 mpox confirmed in the UK, the UK Health Security Agency has confirmed.

A National Institute of Allergy and Infectious Diseases colourised transmission electron micrograph of mpox particles (red) found within an infected cell (blue). (AP)

How did monkeypox outbreak of 2022 first occur in the UK?

News about outbreaks in the UK first hit the headlines in 2022 and escalated throughout the year.

On 7 May, the UK Health Security Agency (UKHSA) confirmed a case of mpox had been found in an individual who had returned to England from Nigeria.

By 16 May four additional cases had been detected in the UK, bringing the nationwide total to seven.

At the time, the UKHSA said the new cases, identified in London and the northeast of England, did not have known connections with previous infections but it warned there was evidence of community transmission of the disease.

Prior to 2022, cases diagnosed in the UK had been either imported from countries where mpox is endemic or through contacts with documented epidemiological links to imported cases.

The UK government in May said it was “cautious but not concerned” about the mpox virus. This was at a time when Covid was still a considerable concern.

By August 2022, cases had risen to 2,859 and transmission had been linked to close contact with a person, such as sexual relations.

Although mpox was not generally a sexually transmitted infection in 2022-23, it was suggested by public health officials that the outbreaks were linked to sexual activity - with the majority, but not all, cases amongst men who have sex with men.

In December 2022 cases had hit 3,732.

Vaccines introduced

Shortly after the initial outbreak, the UK began rolling out mpox vaccines to at-risk individuals. The vaccine was called the Imvanex vaccine, which is typically used against smallpox, a viral relative of monkeypox.

A second dose of vaccines was offered from September 2022.

The move at the time was spurred by new modelling which found that vaccinating 25 per cent of men who have sex with men, targeting those who have a higher number of partners, could reduce the spread of the virus by 70 per cent.

In June this year, volunteers were being sought to test a new mRNA vaccine for monkeypox.

How many cases were reported in 2023-24?

Data published by the UKHSA in 2023 and 2024 - up to 30 June - reported 239 cases of mpox in the UK.

Of the 225 cases in England, 98 were presumed to have acquired mpox in the UK, 74 were acquired outside the UK and the remaining 53 were awaiting classification.

The monthly number of cases over this period ranged from one to 31, compared to the monthly high of 1,339 in July 2022.