The World Health Organisation is set to decide whether to declare monkeypox a global health emergency, stirring criticism from leading African scientists who say it has been a crisis in their region for years.

The deliberations and scrutiny of the WHO's response to the outbreak follows concerns over how the United Nations agency and governments worldwide handled COVID-19 in early 2020.

A "public health emergency of international concern" is WHO's highest level of alert.

The agency does not declare pandemics but it did start using the term to describe COVID-19 in March 2020.

For many governments, that - rather than WHO's earlier declaration of an emergency in January - was the moment they began to take real action to try to contain COVID-19, which proved to be too late to make a difference.

Monkeypox does not spread nearly as easily as COVID-19 and there are vaccines and treatments available, unlike for the coronavirus when it emerged.

But it has still raised alarm.

The case count from the current outbreak outside of Africa has topped 3000 in more than 40 countries, according to a Reuters tally - largely among men who have sex with men - since it was first reported in May.

There have been no reports of deaths.

The viral disease, which causes flu-like symptoms and skin lesions, is endemic in parts of central and west Africa.

The continent has registered about 1500 suspected cases since the start of 2022, of which 66 have been fatal, according to official data.

"When a disease affects developing countries, it is (apparently) not an emergency. It only becomes an emergency when developed countries are affected," said Professor Emmanuel Nakoune, acting director of the Institut Pasteur in Bangui, Central African Republic, who is running a trial of a monkeypox treatment.

Still, Nakoune said that if the WHO declares an emergency in the case of monkeypox, it would still be an important step.

"If there is the political will to share equitably the means of response between developed and developing countries..., each country will be able to benefit," he said.

At an online briefing with reporters on Thursday, the acting director of the Africa Centres for Disease Control and Prevention, Ahmed Ogwell Ouma, said monkeypox case and death numbers were already at "emergency levels" on the continent.

The WHO will convene a closed meeting of experts at 12pm in Geneva.

It remains unclear when the decision will be announced.

The emergency committee meeting on Thursday includes experts from the most affected regions, who have also consulted with scientists including Nakoune.

They will make a recommendation to WHO Director-General Tedros Adhanom Ghebreyesus, who makes the ultimate decision on whether to call the emergency.

The step mainly functions to sound the alarm and can prompt further guidance from the WHO, as well as focus attention among member countries.

The WHO has already provided detailed guidance on the outbreak and said it is working on a mechanism for sharing treatments and vaccines.