Monkeypox: Key questions answered.

Cases are rising worldwide, leaving some people anxious that the virus could evolve into a pandemic alongside covid-19. Michael Le Page addresses monkeypox's risks.

WITH monkeypox cases appearing globally (see page 7), some with no obvious source of infection, it seems the virus may be spreading undetected. While not as serious a disease as covid-19, it is understandable that some people feel a sense of familiarity with the early days of the coronavirus pandemic. Here are the key facts you need to know as the outbreak unfolds.

What is monkeypox?

Monkeypox is a disease caused by a virus that, as the name suggests, usually spreads among monkeys in Central and West Africa, but occasionally jumps to people.

It was first spotted in monkeys in labs in 1958. The first human case was identified in what is now the Democratic Republic of the Congo in 1970.

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 and Prevention (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 UK Health Security Agency (UKHSA) saying the risk to the UK population amid the ongoing outbreak “remains low”.

Monkeypox can also spread via contact with clothing or bedding used by an infected person.

1958 The year monkeypox was first identified in monkeys

1 in 100 The death rate of the West African monkeypox strain in known cases

170+ The number of confirmed or suspected cases worldwide so far

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.

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 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. This information isn't yet available for all of the other affected countries.

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 as Tpoxx) is approved in most of 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 most of 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 Central and West Africa before?

There have been several monkeypox outbreaks outside these regions, but usually involving only a handful of cases with very limited local spread. In 2018, a person arriving from Nigeria spread the virus to two people in the UK. In 2021, the UK reported three cases in one household, one member of which had travelled to Nigeria.

It's important not to put this on the same levels as a novel coronavirus

This week, it was revealed that one of these 2021 cases was treated with tecovirimat. This may have shortened the duration of their illness, as their viral load fell immediately after treatment began (The Lancet Infectious Diseases, DOI: 10.1016/S1473-3099(22)00228-6).

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 this strain is more transmissible than others. But chance events can help a virus spread more widely, such as being carried by a “superspreader”.

A team in Portugal has released a draft genome of the virus behind the ongoing outbreak, confirming it is the West African variant and most closely related to the virus responsible for much smaller outbreaks in the UK, Singapore and Israel in 2018 and 2019.

It is unclear whether this virus has mutated to become more transmissible. Viral sequencing is ongoing, but establishing whether the circulating virus is unique won't be easy, given its large and complex genome.

Could this become another pandemic?

The expectation is this outbreak can be contained by contact tracing. The UK is offering vaccines to contacts regarded as being at high risk of infection. While researchers aren't totally 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 John Brownstein at Boston Children's Hospital. “It's important not to put this on the same level as a novel coronavirus.”