Monkeypox: Some Keys to Understand This Emerging Disease

Abstract

In 1958, several monkeys in a Copenhagen laboratory developed a skin rash from which an orthopoxvirus could be isolated, which was named monkeypox virus (MPXV). However, the natural animal reservoir for MPXV is thought to be a rodent. The first human case occurred in 1970, and the incidence has increased progressively throughout the years. Starting May 2022, the number of cases outside Africa has soared, especially in Western Europe. There are two clades of MPXV, Congo Basin, with higher virulence and mortality, and Western Africa (WA). MPXV from the present outbreak has been proposed to be classified as Clade 3, distinct from the WA clade by at least 50 substitutions, which may increase human-to-human transmissibility. Most cases correspond to men in their 30s who have sex with men, and the possibility of sexual transmission is under investigation. Though there is no evidence of human-to-animal transmission, pets of positive human cases may be classified as low risk, including dogs, cats, and birds, who can be quarantined at home, and high risk, such as pet rabbits or mice, who should be isolated in official laboratories for observation. The current epidemiological data do not support the risk of a pandemic.

Keywords: animals; diagnosis; epidemiology; genome; monkeypox; transmission; treatment.

Figure 1

Species that have been found to be positive, either by virus isolation or presence of antibodies, and area of origin. Rodents are written in pink boxes; non-human primates in orange boxes and the species that were affected at the Rotterdam Zoo in a blue box.

Figure 2

Open reading frames (ORF) identifiable in the monkeypox virus reference sequence (NC_063383; 197,209 bp) (above), and genomic sections in which they are organized (below). Adapted from GenBank and ViralZone.

Figure 3

Signs and symptoms among confirmed cases of monkeypox (showed in percentage of presentation). Globally, as of 8 July 2022 [73].