Clades of Monkeypox and its place in the pox family
Monkeypox is a double-stranded DNA virus of the poxvirus family, with two clades—Clade I and Clade II. These clades were known to circulate in different regions in Central Africa and West Africa, respectively. Historical outbreak data suggests that Clade I is more transmissible and is more severe than Clade II. Genomes from the current outbreak belong to the subclade IIb.
For many decades now, monkeypox has been considered a potential biological threat, and vaccines and antivirals have been in development, led by initiatives in the United States. Monkeypox is related to the smallpox virus (variola virus) but is less transmissible and causes less severe disease than the latter. During the eradication efforts for smallpox in the 1970s, the smallpox vaccine was found to prevent the related illnesses of monkeypox (85 percent from observational studies) and cowpox. It is likely that people who were vaccinated against smallpox (before its eradication in 1980) will have some protection from monkeypox. However, the level of cross-protection it might provide remains unclear. Monkeypox is not related to the varicella-zoster virus (Human Alphavirus 3) that causes the disease varicella/chickenpox/shingles, even though the appearance of rashes and other symptoms can be similar. Both are DNA viruses but too distant from each other in the tree of life to offer cross-protection.