More than 500 mpox patients have fled clinics in eastern Democratic Republic of Congo over the last month amid the current conflict.

Officials at Africa Centres for Disease Control and Prevention (Africa CDC), a leading health agency on the continent, have said they are worried as the missing patients risk spreading the highly contagious disease that is suspected to have killed at 900 people in DR Congo last year.

The patients fled from facilities in Goma and Bukavu - two cities that descended into chaos as they were seized by the Rwanda-backed M23 rebels over the past weeks.

"We were looted. We lost equipment. It was a disaster," Dr Samuel Muhindo, in charge of a clinic in Goma, told the BBC.

Mpox - formerly known as monkeypox - can cause symptoms such as lesions, headaches and fever.

According to Africa CDC, since the start of this year almost 2,890 mpox cases and 180 deaths have been reported in the country, which has been at the epicentre of several recent outbreaks.

Dr Muhindo described how 128 patients had fled Goma's Mugunga health centre in the wake of the fighting at the end of January.

His health workers had not been able to trace them as paperwork at the clinic was destroyed, he said.

At Bisengimana, a hospital in Goma that also treats mpox, looters took medicines and personal protective equipment.

Fires were lit outside the centre and when the perpetrators departed, patients' medical records were left strewn on the floor.

The situation has been further complicated by the M23's decision to close a network of camps in Goma where tens of thousands of people who had sought refuge from fighting in recent years.

They were given 72 hours to leave last week, although the M23 later said it was encouraging "voluntary returns".

"Now we are afraid of an outbreak of the epidemic in the areas where the displaced people returned to," Dr Muhindo said.

His fears have been echoed by the Africa CDC.

"Once again, we are calling really for the ceasefire and also the agency to establish a humanitarian corridor to facilitate the continuation of mpox interventions," Dr Ngashi Ngongo, Africa CDC's mpox incident manager, said on Thursday.

Over the last week, the Africa CDC says the number of missing mpox patients has risen by 100 as fighting escalates and the rebels take more territory.

Dr Ngongo added that a new variant of mpox with "high potential for higher transmissibility" had also been detected in DR Congo.

The country's ability to respond to the disease has been hampered by the conflict, between the M23 and DR Congo's army, as well as a lack of funding.

The mpox facility at Mugunga, funded by the UN children's agency (Unicef) and UK Aid Direct, managed to reopen last week.

But it is already so overstretched that there are times when four or five patients have to share one bed.

"I first fled from Minova to Goma when the M23 rebels began to advance from there," Sadiki Bichichi Aristide, a 23-year-old being treated at Mugunga along with two of his children, told the BBC.

"I began to fall sick in a [camp for displaced people]. It started with my fingers, and then I had lesions, which began to rupture on my hands. My neighbours told me to go to Mugunga with my children. I left my wife behind."

He said he had seen "so many" people with mpox before he arrived at the clinic last week.

Dr Oummani Rouafi, Unicef's Goma health specialist, told the BBC that the only reason Mugunga hospital had reopened was because staff had managed to hide some equipment and medicine from the looters.

But this had not been the case at many other treatment centres that had been completely ransacked, he said.