Mpox Clade I, one of two types of the virus formerly called monkeypox is spreading quickly in Africa. Mpox Clade I causes more severe illness and death than the other type – mpox Clade 2. More than 18,000 cases have been reported this year, many of them children. At least 600 deaths have been reported.
The World Health Organization declared a public health emergency of international concern last month, due to the rapid spread of mpox Clade 1.
Mpox Clade 1 is believed to be more infectious and more deadly than mpox Clade 2, which caused the global outbreak in 2022 and 2023.
We asked Dean Blumberg, chief of pediatric infectious diseases at UC Davis Children's Hospital, to answer questions about this latest outbreak.
What is a clade and what is the difference between Clade 1 and Clade 2 of mpox?
In biology, a clade is a group of organisms with a common ancestor. The World Health Organization has confirmed that there are two distinct clades of the mpox virus: Clade 1 and Clade 2.
Mpox Clade 2 is what caused the global outbreak of mpox in 2022 and 2023.
Mpox Clade 1 is what is circulating now in Africa — including African countries that haven't reported cases of mpox in the past. As of Sept. 3, 2024, cases have also been reported in Sweden, Thailand and Pakistan after travel to Africa.
What are the signs and symptoms of mpox?
Common symptoms are:
- Rash
- Fever
- Sore throat
- Headache
- Muscle aches
- Back pain
- Low energy
- Swollen lymph nodes
For some, the first symptoms will be similar to influenza or COVID. But the development of the rash is hard to miss. See photos of the mpox rash. The lesions can appear on the hands, feet, chest, face or genitals. It starts as macules, which are flat lesions. Then it forms a firm nodule. From there, it becomes a blister, then a pustule (a blister containing pus) and then it scabs over. It can be painful or itchy. Symptoms typically last two to four weeks, but may last longer in those with weakened immune systems.
How long does it take before symptoms appear?
According to the Centers for Disease Control and Prevention (CDC), the incubation period (the time from when one is infected to when symptoms appear) for mpox is 1-21 days after exposure. During this incubation period, people who are infected may feel fine and have no symptoms. People may be contagious one to four days before symptoms appear and can stay infectious until the skin rash scabs and heals over.
