Less than 3 years ago Mpox was confined almost exclusively to central and west Africa - with only a handful of exported cases - and consisted of two clade (I & II).  Clade II, which was found primarily in the DRC, was the more severe of the two. 

But for years researchers have warned that the Monkeypox virus was becoming more transmissible, and it had the ability to mutate into a more dangerous variant.

A 2016 study (see EID Journal: Extended H-2-H Transmission during a Monkeypox Outbreak) looked at a large 2013 outbreak of Monkeypox in the DRC and suggested that the virus's epidemiological characteristics may be changing (possibly due to the waning smallpox vaccine derived immunity in the community).

The DRC had reported a 600% increase in cases over both 2011, and 2012.  The authors also cite a higher attack rate, longer chains of infection, and more pronounced community spread than have earlier reports.

Like all viruses, Monkeypox continues to evolve and diversify, as discussed in the 2014 EID Journal article Genomic Variability of Monkeypox Virus among Humans, Democratic Republic of the Congo, where the authors cautioned:

Small genetic changes could favor adaptation to a human host, and this potential is greatest for pathogens with moderate transmission rates (such as MPXV) (40). The ability to spread rapidly and efficiently from human to human could enhance spread by travelers to new regions.

And in the spring of 2022, a new clade IIb began spreading internationally, forcing the WHO to declare a PHEIC (Public Health Emergency of International Concern).  While that outbreak slowed over time, at least 100,000 cases were reported outside of Africa. 

In late 2023 another - more formidable - clade Ib clade emerged (see Preprint: Sustained Human Outbreak of a New MPXV Clade I Lineage in Eastern Democratic Republic of the Congo), that was reported to be more transmissible, and potentially more severe.

Today, there are 4 officially recognized clades of the Mpox virus (Ia, Ib, II, IIb), and more could emerge over time. A reminder of what can happen when an emerging virus is allowed to simmer for years without serious interventions.

Last month the WHO published a new, updated risk assessment, which puts the risk of national and international spread of clade Ib as HIGH and Ia, II, and IIb as MODERATE.  

So far, at least 11 non-African nations have reported imported clade IIb cases over the past 6 months. 

As our collective immunity from the smallpox vaccine - which was discontinued in the late 1970s - wanes, there will be increased opportunities for emerging pox viruses to make a comeback.  We ignore them at considerable risk to global public health.