Scientists studying the new strain of mpox, which has spread beyond the Democratic Republic of Congo, say the virus is mutating faster than expected, often in regions where experts lack the funding and equipment to effectively monitor it.

This means there are many unknown factors about the virus itself, the severity of the disease it causes, and how it spreads, complicating the response, six scientists from Africa, Europe, and the United States told Reuters.

Mpox, formerly known as monkeypox, has been a public health issue in parts of Africa since the 1970s, but it did not receive international attention until it emerged globally in 2022, prompting the World Health Organization (WHO) to declare a global health emergency, which was lifted 10 months later.

A new strain of the virus, known as clade 1b, is once again garnering global attention after the WHO declared a new health emergency.

The strain is a mutated version of clade 1, a form of mpox that is transmitted through contact with infected animals and has been endemic in Congo for decades. Mpox causes flu-like symptoms and skin rashes and can be fatal.

Congo reported over 18,000 suspected cases of mpox from clade 1 and clade 1b strains this year, with 615 deaths, according to the WHO. There were also 222 confirmed cases of the clade 1b strain last month in four African countries, along with one case each in Sweden and Thailand, involving individuals who had traveled to Africa.

“I worry that in Africa we are working in the dark,” said Dr. Dimie Ogoina, an infectious disease specialist at Niger Delta University Hospital in Nigeria, who chairs the WHO emergency committee for mpox. He was the first to raise the alarm in 2017 about the potential sexual transmission of mpox, which has now been confirmed.

“We do not fully understand the outbreak we are dealing with, and if we don’t understand it well, we will struggle to address the problem in terms of transmission dynamics, disease severity, and risk factors,” Ogoina said. “And I am concerned that the virus seems to be mutating and producing new strains,” he added.

He noted that the clade 2b strain in Nigeria took five years or more to evolve enough to spread among humans, leading to the 2022 outbreak. The clade 1b strain has done the same in less than a year.