Monkeypox virus particles captured via a coloured transmission electron micrograph
UK HEALTH SECURITY AGENCY/SCIENCE PHOTO LIBRARY
There is growing concern about an outbreak of monkeypox, with dozens of confirmed cases and more emerging by the day.
Here is what we know so far:
What is monkeypox?
Monkeypox is a disease caused by a virus that usually spreads among animals such as rodents in Central and West Africa, but occasionally jumps to people, causing small outbreaks.
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It was first spotted in monkeys in labs in 1958, hence the name. The first human case was identified in what is now the Democratic Republic of the Congo in 1970.
How many cases are there in the current outbreak?
At time of publication, 109 monkeypox cases are either confirmed or suspected worldwide, according to a list of reports being compiled by Moritz Kraemer at the University of Oxford, John Brownstein at Boston Children’s Hospital and their colleagues.
The UK has nine confirmed cases, mostly in London. Portugal has 14 confirmed and 20 suspected cases, while Spain has seven confirmed and 24 suspected cases. Italy has two suspected cases, while Belgium has two suspected cases and one confirmed. France and Sweden have one confirmed case each.
The US has one confirmed and one suspected case. Canada has one confirmed and 21 suspected cases. Australia has one confirmed and one suspected case.
Kraemer and Brownstein think these cases could be the tip of the iceberg. “It’s probably more widespread than we are currently detecting,” says Kraemer.
Are the cases linked?
That isn’t yet clear, say Kraemer and Brownstein.
The first person confirmed to be infected in the UK had travelled to Nigeria. They developed a rash on 5 May and were hospitalised on 6 May, but have fully recovered. Two of the other UK cases are linked to this first one, but the latest four cases in the UK have no known links to previous cases, according to the UK Health Security Agency (UKHSA).
The monkeypox virus is now spreading from person to person in the countries with known cases, Susan Hopkins at the UKHSA said in the organisation’s latest update. “These latest cases, together with reports of cases in countries across Europe, confirm our initial concerns that there could be spread of monkeypox within our communities,” she said.
The UK’s most recent cases are predominantly in gay men, bisexual men and men who have sex with men, according to the UKHSA. “We are particularly urging men who are gay and bisexual to be aware of any unusual rashes or lesions and to contact a sexual health service without delay if they have concerns,” said Hopkins.
How does it spread?
According to the World Health Organization (WHO), “monkeypox can be transmitted by droplet exposure via exhaled large droplets and by contact with infected skin lesions or contaminated materials”. Some might interpret this as meaning the virus is airborne, but the WHO doesn’t use this term.
The US Centers for Disease Control (CDC) states: “Human-to-human transmission is thought to occur primarily through large respiratory droplets. Respiratory droplets generally cannot travel more than a few feet, so prolonged face-to-face contact is required.”
But the virus doesn’t usually spread easily between people, with the UKHSA saying the risk to the UK population amid the ongoing outbreak “remains low”.
Monkeypox can also spread through close contact or by contact with clothing, towels or bedding used by an infected person.
It isn’t regarded as a sexually transmitted infection, but it can be passed on during sex via skin-to-skin contact, says the UKHSA.
Monkeypox can also be caught from infected wild animals in parts of West and Central Africa. This may occur if you are bitten or if you touch the animal’s blood, bodily fluids, spots, blisters or scabs. Monkeypox may also be transmitted by eating the undercooked meat of an infected animal.
What are the symptoms?
The first symptoms of monkeypox include fever, headache, muscle aches, backache, swollen lymph nodes, chills and exhaustion, says the UKHSA.
A rash can also develop, typically on the face first and then on other parts of the body including the genitals. The rash can initially look like chickenpox, before forming scabs.
How deadly is it?
Monkeypox is usually mild, with most people recovering within a few weeks without treatment.
In Africa monkeypox can be deadly in as many as 1 in 10 people who contract the disease, according to the CDC. However, there are two main types of monkeypox: the Congo strain and the West African strain. The WHO states that the 1 in 10 figure applies to the Congo strain and the West African strain is deadly in around 1 in 100 reported cases.
Amid the ongoing outbreak, only the West African strain has been identified in the UK. Virus sequencing information isn’t yet available for elsewhere in the world.
What’s more, the WHO says these figures refer to the proportion of deaths in those confirmed to be infected, called the case fatality ratio. But with diseases whose symptoms can be mild, many cases go undetected, meaning the infection fatality ratio – the proportion of deaths among all those infected – can be substantially lower.
According to the WHO, children with monkeypox are more likely than adults to become seriously ill.
Becoming infected during pregnancy can also lead to complications, including stillbirth.
Are there any treatments or vaccines?
Yes. The antiviral drug tecovirimat (also sold under its brand name Tpoxx) is approved in Europe for treating monkeypox, smallpox and cowpox. It is only approved for smallpox in the US. In animal studies, tecovirimat significantly increased the survival rate of animals given very high doses of monkeypox.
There is also a vaccine called Jynneos (also known as Imvanex and Imvamune), which is approved in the US and Europe for preventing monkeypox and smallpox in people aged over 18.
In addition, those who are old enough to have been vaccinated against smallpox as babies should have some protection. Routine smallpox vaccination ended in the UK in 1971 and in the US in 1972.
Have there been outbreaks outside Africa before?
There have been several monkeypox outbreaks outside Africa, but usually involving only a handful of cases with very limited local spread. In 2021, for instance, the UK reported three cases in one household, one member of which had travelled to Nigeria. In 2018, a person arriving from Nigeria spread the virus to two people in the UK, including one healthcare worker.
Does that mean the current outbreak is the largest ever?
No, there have been larger outbreaks in Africa. For instance, in 2001 and 2002, 485 cases and 25 deaths were reported in the Democratic Republic of the Congo, where the virus is present in monkeys.
In 2017 and 2018, 122 confirmed or probable cases were reported in Nigeria, with seven deaths. Many cases probably also go unreported.
Could this outbreak be caused by a new strain of monkeypox?
That remains unknown. The fact that so many cases are being reported in several countries certainly suggests that this strain is more transmissible than others. But chance events can help a virus spread more widely, such as being carried by a “superspreader”.
“It’s way too early to have any insights into what is happening,” says Brownstein.
Health officials are sequencing samples of the virus, which will reveal if it is significantly different to previously identified variants of the West African strain and if all known cases are related.
Could this become another pandemic?
The expectation is this outbreak can be contained by contact tracing, like all previous monkeypox outbreaks. The UK is offering vaccines to contacts regarded as being at high risk of infection to help ensure the virus doesn’t continue spreading.
While researchers aren’t completely ruling out a pandemic, they don’t think it is at all likely. “I don’t think the science points to that at this moment,” says Brownstein. “It’s important not to put this on the same level as a novel coronavirus.”
Some researchers have previously warned that monkeypox is a growing threat. “The emergence of monkeypox as a significant human pathogen is indisputably a realistic scenario,” states a 2018 paper.
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Article amended on 20 May 2022
This article has been amended to correct Brownstein’s affiliation and Tpoxx’s geographical approval.
Article amended on 6 June 2022
This article has been amended to correct the animals monkeypox usually infects.
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