The World Health Organisation (WHO) has declared the highly infectious disease Mpox a global health emergency, for the second time in two years.

The disease - formerly known as monkeypox - has killed at least 450 people during an initial outbreak in the Democratic Republic of Congo.

It has now spread across parts of central and east Africa, and scientists are concerned about how fast a new variant is spreading, and its high fatality rate.

WHO chief Tedros Adhanom Ghebreyesus said the potential for further spread within Africa and beyond "is very worrying".

"A co-ordinated international response is essential to stop this outbreak and save lives," he said.

By declaring the Mpox outbreak as a public health emergency, it's hoped research, funding, and the introduction of other international public health measures will be accelerated.

Two main strains of the virus have been circulating.

Clade I is endemic in central Africa, but Clade Ib is a new, more virulent form of the virus, which one scientist has described as the "most dangerous yet".

How it spreads

It spreads through close contact with someone who is infected - for example, through sex, skin-to-skin contact and talking or breathing close to another person.

The disease can cause lesions across the whole body, and in some cases can be deadly.

Since the start of the year, there have been more than 13,700 cases of the disease in the DR Congo, with at least 450 deaths.

It has since been detected in other African countries - including Burundi, the Central African Republic, Kenya and Rwanda.

It's not the first time that the WHO has declared a public health emergency over an mpox outbreak - in July 2022 a milder strain, called Clade II, spread to nearly 100 countries, including some in Europe and Asia.

That outbreak was brought under control by vaccinating vulnerable groups.

On Tuesday, scientists from the Africa Centres for Disease Control and Prevention declared a public health emergency.