A senior official of the World Health Organization (WHO), Rosamund Lewis, has said that the body is “very worried” about the spread of a variety of Mpox that has killed nearly 600 people in the Democratic Republic of Congo this year.

This year alone, Congo DR has reported 13,000 cases, which is more than twice as many as during the last peak in 2020, with the disease occurring in almost every province. The WHO is working with the authorities on the response and a risk assessment.

The dangerous clade mpox outbreak was the subject of a warning released by the U.S. Centre for Disease Control and Prevention (CDC) on Thursday.

“The virus variant is known to be more virulent. If it adapts better to human-to-human transmission, that presents a risk,” Lewis, WHO’s mpox lead, told journalists.

WHO in May announced that the disease was no longer a global health emergency after which its director-general, Tedros Adhanom Ghebreyesus, declared the end of the emergency status for the disease.

Most reported cases of the disease were identified through sexual health or other health services in primary or secondary healthcare facilities, and involved mainly, but not exclusively, men who have sex with men.

A less severe form known as clade II started to spread around the world last year, mostly through male-to-male sexual contact, prompting WHO to declare a public health emergency.

Lewis expressed concern over new evidence suggesting that clade I can also spread through sexual contact. According to her, mumps can also infect humans through contaminated animals or family members living together in a home. Children and those with weakened immune systems are particularly vulnerable; in up to 10% of cases of clade I, illness results in death.

“We have very little information of who is dying of mpox [in DRC] other than age,” said Lewis, adding more data was needed.

The viral infection known as mpox spreads by intimate contact and results in lesions filled with pus and flu-like symptoms. Although most cases are mild and can be fatal.