The disease, formerly known as monkeypox, has spread rapidly across Central and East Africa since the start of the year. The initial outbreak was in the Democratic Republic of Congo, which has now registered 15,600 cases since the start of the year and more than 500 deaths.

Health officials say the new strain of Mpox may be the most deadly yet.

Joe Inwood reports. It starts with flu-like symptoms and ends with this.

This is what Mpox, which used to be called monkeypox, can do.

Here in the Democratic Republic of Congo, the virus is common, but it's spreading.

It's transmitted by physical contact or through the air. Five-year-old Sandrine has now recovered, but it was a terrifying moment for her mum.

She had a high fever, and then she started to get lesions on her body.

She had rashes on her arms, on her abdomen, and even on her tongue.

I'd been told it was a serious illness that could kill her, so I took her to the hospital. Although it can be sexually transmitted, in the crowded camps of the Eastern DRC, most of the patients are children.

So far, we have 130 suspected cases, and half of them under five.

Just 5% are adults.

The most common way to get infected is direct contact from a sick person, and in the camps, children, they play together. The latest outbreak has killed 450 people in the DRC.

It seems a new variant, called PLAID-1B, is more virulent and more dangerous, and it's now been detected in neighboring countries, including Burundi, Kenya, Rwanda, Uganda, and the Central African Republic.

And so the World Health Organization has declared a global health emergency.

It's clear that a coordinated international response is essential to stop these outbreaks and save lives. A public health emergency of international concern is the highest level of alarm under international health law.

It is possible to vaccinate against Mpox, as happened in previous outbreaks, but these vaccines are not widely available in the DRC, where these children had to rely on their immune systems.

The WHO is warning if more is not done to stop the spread of this new variant, there could be serious consequences on these camps. Joe Inwood, BBC News.