Mpox, M is for “Maybe…”

By: Adhella Menur

2017-2018

The last reported human Mpox case in Nigeria was in 1978
In 2017, an 11-year-old boy from Bayelsa was hospitalized with lesions resembling chicken-pox, but also affected the soles and palms—areas not typically involved. His family members developed similar symptoms.
• The boy and his uncle had been in contact with a neighborhood monkey, and the uncle had other potential exposures, including visit-ed slaughterhouses for the restaurant, and had visited a sex worker a week before becoming ill.
Prof. Dimie Ogoina, an infectious disease specialist, suspected Mpox and alerted the Nige-ria-CDC.
80% of cases involved young men with genital lesions, and there were signs of new patterns of transmission.
Early on, Prof. Ogoina raised concerns about possible links to high-risk sexual behaviors, though these ideas initially faced skepticism. A thoughtful story on the Mpox outbreaks in Nigeria by Jon Cohen and Abdullahi Tsanni can be found in Science (doi: 10.1126/science.z3d5uwl).
Between 2018 and 2021, the United Kingdom, the U.S., Israel, and Singapore reported nine human Mpox cases, all involving travel history from Nigeria. Three of the cases were men who had genital lesions.
Mpox cases continue to be reported regularly in African countries.

2022-2023

The first Mpox cluster was identified in the UK, with the initial case detected in London on May 6, 2022, in a patient who had recently traveled from Nigeria.
Mpox cases also began appearing in Europe and US countries, predominantly among men who have sex with men (MSM) after festivals.
Subsequently, many countries reported Mpox cases, affecting diverse populations.
This marked the first time Mpox cases surged rapidly in non-endemic countries worldwide, with how the virus’s spread to some regions still not fully understood.

On July 23, 2022, the WHO declared the Mpox outbreak a Public Health Emergency of International Concern (PHEIC) – ended in May 2023. In November 2022, the WHO renamed Monkeypox to Mpox to avoid misperception, racist, and discriminatory connotations.

2023 – ongoing

It began in the fall of 2023 in Kamituga, DRC, that previously had been Mpox-free. The most affected group were sex workers.
There was also a drastic surge in Mpox cases, affecting many children.
Currently, over 24,000 confirmed or suspected Mpox cases, including more than 600 deaths, were reported across Africa.
This outbreak is complex → scientists hypothesize multiple outbreaks are occurring simultaneously: Clade Ia (older variant) and Clade Ib (novel variant) in the DRC and neighboring countries, and Clade II in South Africa, primarily in people living with HIV.
Outside of Africa, the novel Mpox strain (Clade Ib) cases have been reported in Sweden and Thailand, both linked to recent travel from African countries.

M for “Meet” the virus

Family Poxviridae, genus Orthopoxvirus.
Same group with variola (smallpox), cowpox, and vaccinia virus.
The MPXV genome is about 197,000 kb.
The mutation rate is lower than RNA viruses → 2 nucleotide substitutions/ genome/ year.
However, the virus from the 2022 pandemic showed a rapid evolution → resulting from continued interaction with the human immune system since 2016.
Most new mutations were characterized by activity of an anti-viral enzyme in the human immune system called APOBEC3 → sustained human-to-human transmission.

Ia -> classic form, 1970-present. Primarily animal-to-human (limited human-to-human transmission). High proportion in children <15 years. More clinically severe. CFR up to 11%.

Ib → novel, 2023-present. Differ from Ia; Ib linked to sexual contact (sex worker >>) – CFR <4%? – still under investigation. CFR up to 11%.

IIa → classic form, 1970-present. Responsible for 2003 US outbreak. Primarily animal -to-human (limited human-to-human transmission). Milder than clade I. CFR <2%.

IIb → (actually found in 1971?) 2017-present. Responsible for 2022 pandemic (lineage B.1). Primarily human-to-human transmission, high proportion in young adults (MSM >>). CFR <2%.

M for “Modes” of transmission and “Manifestations”