MICROBIOLOGY

• DNA virus and a member of the orthopoxvirus genus of the Poxviridae family, monkeypox is similar to smallpox (variola virus), smallpox vaccine (vaccinia virus), and cowpox virus.
  • In November 2022, the WHO renamed "monkeypox" to "mpox," allowing for a 1-year transition during which both names would be recognized. In 2025, the CDC reverted to monkeypox as its preferred designation.
    • The idea was to reduce the stigma and discrimination associated with the "monkeypox" name and ensure that the infection is not associated much with non-human primates.
  • WHO is using Roman numerals for MPXV variants.
    • The former Congo Basin (Central African) clade is now referred to as Clade I.
      • Has high reported human-to-human transmission rates and mortality (up to 10% historically).
      • It tends to affect children > adults, with higher mortality than Clade II.
        • Recent data suggest < 0.5% for Clade Ib to about 3% for Clade Ia.
    • The former West African clade is Clade II.
      • Clade IIa
        • It causes a mild illness with limited human-to-human transmission and low mortality (~1-3%).
      • Clade IIb refers to variants that circulated during the 2022 global outbreak.
• Although initially named monkeypox, the animal reservoir is believed to be African rodents; however, this has not been fully defined.