Sex, a hex and a sick child offer clues to the mpox epidemic's birth

On Sept 30, 2023, an anxious father took his five-year-old son to the hospital in Kamituga, a muddy, bustling town carved out of the thick forest in eastern Congo.

The boy had a high fever and oozing sores on his torso and face. Nurses diagnosed chickenpox. They admitted him to the paediatric ward and tried to manage his fever.

Days passed and the child's health did not improve. His fever climbed higher and the lesions spread.

Perplexed, the paediatric staff called Dr Steeve Bilembo, who was managing urgent care. He and a trusted nurse colleague, Mr Fidele Kakemenge, examined the boy and quickly eliminated possibilities: not chickenpox, not measles, not rubella, not a bad case of dermatitis.

The spreading sores meant it was not malaria, typhoid or cholera.

"And then at one point, we said, 'Could it be mpox?'" Dr Bilembo recounted. "Although we have never seen it - only in books."

They looked it up and quickly confirmed that the child had all the symptoms of mpox. Yet, it made no sense.

Although mpox was first discovered in Congo in 1970 and has been endemic in the country ever since, the disease circulated in remote villages in the centre of the country - 2,000km away. It was unknown in the east.

How could a boy who had never left Kamituga have mpox?

It was the start of a medical mystery that would reveal swift and startling changes in a virus once considered a familiar foe, lead to the declaration of a global public health emergency and draw scientists from around the world on a days-long journey along a muddy, rutted track that is the only way to reach Kamituga.

Fifteen months later, the new strain of the virus has spread to six other countries through East and southern Africa, according to the Africa Centres for Disease Control and Prevention, and individual cases have turned up in Europe, Asia and North America as well.

The virus seems to have adapted to spread more easily and quickly between people. More than 62,000 cases of mpox have been reported in Africa in 2024, three-quarters of them in Congo.