LONDON — As the World Health Organization's emergency committee convened Thursday to consider for the second time within weeks whether to declare monkeypox a global crisis, some scientists said the striking differences between the outbreaks in Africa and in developed countries will complicate any coordinated response.

African officials say they are already treating the continent's epidemic as an emergency. But experts elsewhere say the mild version of monkeypox in Europe, North America and beyond makes an emergency declaration unnecessary even if the virus can't be stopped. British officials recently downgraded their assessment of the disease, given its lack of severity.

“I remain concerned about the number of cases, in an increasing number of countries, that have been reported,” WHO Director-General Tedros Adhanom Ghebreyesus told the emergency committee as its meeting got underway.

He said it was “pleasing” to note falling numbers of monkeypox cases in some countries but that the virus is still increasing elsewhere and that six countries reported their first infections last week.

Monkeypox has been entrenched for decades in parts of central and western Africa, where diseased wild animals occasionally infect people in rural areas in relatively contained epidemics. The disease in Europe, North America and beyond has circulated since at least May among gay and bisexual men. The epidemic in rich countries was likely triggered by sex at two raves in Spain and Belgium. The disease can infect anyone in close, physical contact with a monkeypox patient.

Some experts worry these and other differences could possibly deepen existing medical inequities between poor and wealthy nations.

There are now more than 15,000 monkeypox cases worldwide. While the United States, Britain, Canada and other countries have bought millions of vaccines, none have gone to Africa, where a more severe version of monkeypox has already killed more than 70 people.

“What’s happening in Africa is almost entirely separate from the outbreak in Europe and North America,” said Dr. Paul Hunter, a professor of medicine at Britain’s University of East Anglia who previously advised WHO on infectious diseases.

Dr. Placide Mbala, a virologist who directs the global health department at Congo’s Institute of National Biomedical Research, said there are noticeable differences between patients in Africa and the West.

He said different approaches in different countries will likely be needed to stop the global outbreak, making it challenging to adopt a single response strategy worldwide, like those for Ebola and COVID-19.