What is mpox? Two more cases of deadly new variant detected in UK

Two more cases of a potentially deadly and more transmissible strain of mpox have been detected in the UK.

It comes nearly one week after the country's first case of Clade Ib mpox was confirmed in London. The UK Health Security Agency (UKHSA) says the latest cases were household contacts of the first patient.

This brings the total number of known cases of Clade 1b in the country to three, with the UKHSA saying risk to the UK population remains "low". The two latest patients are currently under specialist care at Guy’s and St Thomas’ NHS Foundation Trust in London.

Last Wednesday the first patient, who had recently travelled to countries in Africa that are seeing community cases of Clade Ib, was admitted to the Royal Free Hospital's high consequence infectious diseases unit.

UKHSA chief medical adviser Professor Susan Hopkins said: "Mpox is very infectious in households with close contact and so it is not unexpected to see further cases within the same household.

"The overall risk to the UK population remains low. We are working with partners to make sure all contacts of the cases are identified and contacted to reduce the risk of further spread."

Contacts of all three cases are being followed up by UKHSA and partner organisations. All three patients will be offered testing and vaccination as needed and advised on any necessary further care.

Mpox, previously known as monkeypox was declared a global health emergency this year after it began spreading rapidly across central Africa and popping up around the world – including in Europe.

Mpox has been known about for years and while a concern to the World Health Organization (WHO) it has never been widespread. But in a recent explosion of cases in the Democratic Republic of Congo, alongside changing symptoms has caused alarm for medical professionals.

The WHO declared it an emergency in August following a meeting at the United Nations, with the Africa Centre for Disease Control and Prevention swiftly following suit. A report by the two organisations said there have been more than 40,000 mpox cases linked to almost 1,000 deaths in Africa as of the end of September.

The first confirmed case of Clade I in Europe was in Sweden in August.

So far, the vast majority of all cases and deaths are in DR Congo. However, scientists are concerned about the spread of the new version of the disease that might be more easily transmitted among people.

What is mpox?

Mpox, also known as monkeypox, was first identified by scientists in 1958 when there were outbreaks of a "pox-like" disease in monkeys. Until recently, most human cases were seen in people in central and West Africa who had close contact with infected animals.

In 2022, the virus was confirmed to spread via sex for the first time and triggered outbreaks in more than 70 countries across the world that had not previously reported mpox.

Mpox belongs to the same family of viruses as smallpox but causes milder symptoms like fever, chills and body aches. People with more serious cases can develop lesions on the face, hands, chest and genitals. Earlier this year, scientists reported the emergence of a new form of mpox in a Congolese mining town that can kill up to 10% of people and may spread more easily.

Read more: Mpox: UK preparing for mpox cases after virus declared global emergency

Unlike in previous mpox outbreaks, where lesions were mostly seen on the chest, hands and feet, the new form of mpox causes milder symptoms and lesions on the genitals. That makes it harder to spot, meaning people might also sicken others without knowing they’re infected.

During the global outbreak of mpox in 2022, gay and bisexual men made up the vast majority of cases and the virus was mostly spread through close contact, including sex. Although some similar patterns have been seen in Africa, children under 15 now account for more than 70% of the mpox cases and 85% of deaths in Congo.

The UKHSA says Clade Ib is "different to mpox Clade II that has been circulating at low levels in the UK since 2022, primarily among gay, bisexual and other men-who-have-sex-with-men".

How contagious is mpox?

Mpox can be transmitted by close physical contact with the scabs or blisters it causes.

There is also a risk from contact with bodily fluids such as saliva or snot; contact with bedding or towels or clothing; and a possibility of spread through close and prolonged face-to-face contact such as talking, breathing, coughing, or sneezing, the UKHSA says.

While always known to be infectious in the past, the recent outbreak is on a far bigger scale than previous incidents.

The number of cases has jumped dramatically in recent months, with the Africa CDC reporting last week that the virus has been detected in 19 countries in the continent. As of the end of July, the agency said cases were up 160% compared to the same period last year, while deaths increased by 19%.

Is there a vaccine for mpox?

Yes, after the 2022 outbreak of mpox in dozens of countries was largely shut down with the use of vaccines and treatments in rich countries, in addition to convincing people to avoid risky behaviour.

The DR Congo has received around 265,000 vaccine doses, donated by the European Union, the United States and the Vaccine Alliance, although health experts warn it is still a challenge delivering the vaccine to more remote communities.

An estimated 50,000 people in the DR Congo and Rwanda have been immunised, according to the WHO, which falls well short of the countries' respective populations of 110 million and 14 million.

The organisation says 900,000 doses have been allocated to nine countries based on public health need, adding that it expects almost six million doses to be available by the end of 2024.