Monkeypox has been declared a 'global health emergency' by the World Health Organization (WHO).
More than 16,000 cases of the disease have been reported in 74 countries since around May, according to the US Centres for Disease Control and Prevention.
In the past, the WHO has declared emergencies for public health crises such as the Covid pandemic, the 2014 West African Ebola outbreak, the Zika virus in Latin America in 2016 and the ongoing effort to eradicate polio.
Here's everything you need to know.
What is monkeypox?
Monkeypox is a rare infection. It's mainly spread by wild animals in parts of west or central Africa, which is what makes the recent cases elsewhere in the world unusual.
In Europe, North America and elsewhere, monkeypox is spreading among people with no links to animals or recent travel to Africa.
How many cases are there in the UK?
There were 2,208 confirmed cases in the UK as of July 21, the UK Health Security Agency (UKHSA) has confirmed.
Of these, 2,115 are in England.
The UKHSA said that while anyone can catch monkeypox, the majority of UK cases are in gay, bisexual and other men who have with men.
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What are the symptoms?
It usually takes between five and 21 days for the first symptoms of the infection to appear.
The first symptoms of monkeypox include:
a high temperature
A rash, which often begins on the face before spreading, usually appears one to five days after the first symptoms.
The rash, sometimes confused with chickenpox, starts as raised spots before becoming small fluid-filled blisters. The blisters eventually form scabs and later fall off.
Symptoms usually clear up in two to four weeks.
Is monkeypox dangerous?
Most people recover within a few weeks but severe illness can occur in some individuals.
To date, monkeypox deaths have only been reported in Africa, where a more dangerous version of the virus is spreading, mainly in Nigeria and Congo.
How does monkeypox spread?
You can catch monkeypox from an infected animal if you're bitten or you touch its blood, body fluids, spots, blisters or scabs.
It may also be possible to catch monkeypox by eating meat from an infected animal that has not been cooked thoroughly, or by touching other products from infected animals (such as animal skin or fur).
It can also be spread through close contact with other people, such as:
touching clothing, bedding or towels used by someone with the monkeypox rash
touching monkeypox skin blisters or scabs
through the coughs or sneezes of a person with a monkeypox rash
WHO’s top monkeypox expert, Dr. Rosamund Lewis, said this week that 99% of all the monkeypox cases beyond Africa were in men and that of those, 98% involved men who have sex with men.
Experts suspect the monkeypox outbreaks in Europe and North America were spread via sex at two raves in Belgium and Spain.
The UK Health Security Agency said: "The most recent cases are in gay, bisexual and other men who have sex with men communities, and as the virus spreads through close contact, we are advising these groups to be alert to any unusual rashes or lesions on any part of their body, especially their genitalia, and to contact a sexual health service if they have concerns."
What is the treatment for monkeypox?
Monkeypox is usually a mild illness and most people recover within a few weeks without needing treatment.
But if your symptoms are more severe and you become unwell, you may need hospital treatment.
If you are diagnosed with monkeypox, government guidance is to isolate until:
you have not had a high temperature for at least 72 hours
you have had no new lesions in the previous 48 hours
all your lesions have scabbed over
you have no lesions in your mouth
any lesions on your face, arms and hands have scabbed over, all the scabs have fallen off and a fresh layer of skin has formed underneath
What should I do if I think I have monkeypox?
Anyone who thinks they could be infected is advised to stay home and avoid close contact with other people, including sharing towels or bedding, and to contact GPs or sexual health clinics before visiting in person.
The NHS advises you to call a sexual health clinic if you have a rash with blisters and have either:
been in close contact, including sexual contact, with someone who has or might have monkeypox (even if they have not been tested yet) in the past 3 weeks
been to west or central Africa in the past 3 weeks
You are advised to call a GP if your child has a rash with blisters and has either:
been in close contact with someone who has or might have monkeypox (even if they have not been tested yet) in the past 3 weeks
been to west or central Africa in the past 3 weeks
Is there a vaccine for monkeypox?
Monkeypox is caused by a similar virus to smallpox, and the smallpox vaccine should give a good level of protection against monkeypox, according to the NHS.
The NHS is offering smallpox vaccinations to people who are most likely to be exposed to monkeypox, including:
some healthcare workers
some men who are gay, bisexual or have sex with other men
people who have been in close contact with someone who has monkeypox