An Overview of Monkeypox Virus and Other Medically Important Poxviruses

Abstract

Since the earliest times of history, smallpox left deep traces in the memory of humanity with the great epidemics and destruction (deaths) it caused. Variola virus, which is the causative agent of smallpox, and some other viruses in the same family have been a part of many extraordinary changes in the field of science and medicine. Poxviruses have a privileged position in the scientific world due to the fact that the first examples of immunization (variolation) in ancient civilizations, the first safe vaccines developed for use in humans (cowpox virus, vaccinia virus), first infection model of viral pathogenesis (ectromelia virus), and the first human infection eradicated globally (smallpox). Smallpox virus (variola major) is classified as a biological warfare agent (category A), causing high-mortality infections and epidemics, and remains a worldwide concern. These viruses are also unique with their various biological features. Poxviruses, one of the largest viruses associated with human infections, are widely used as a convenient model in vaccine development and vector-based treatment studies, with large number of protein coding, ability to replicate primarily in the cell cytoplasm (unlike other DNA viruses), and their other advantageous features. More than 10 species of poxviruses cause infections in humans, and except for a few species that are only isolated from humans, these viruses are generally associated with zoonotic infections. Monkeypox virus (MPXV), one of these species, was regarded far from being a threat to humanity in the past due to possible cross-immunity caused by smallpox vaccine. However, local monkeypox cases reported in Central and West Africa in the early 1970s were replaced by small-scale outbreaks in the United States and Sudan in the 2000s, and in the following periods, this virus is considered to be the most important species of the Poxviridae family after the eradication of smallpox virus due to the increasing number of case reports in African countries, especially in the Democratic Republic of Congo and Nigeria. In addition to epidemiological changes that increase the risk of contact with animal reservoirs, the growing proportion of the unvaccinated population and the new and unexpected transmission pattern indicate that human monkeypox infections may continue to intensify. In recent days, while many countries and health authorities have been re-evaluating the existing and potential risks related to monkeypox virus and smallpox virus, some countries have started to take various measures against the possibility of epidemic and biosecurity risks. The main purpose of this article is to consider the general biological characteristics of poxvirus strains, to examine their host distribution, and to provide an overview of the risks attributed to poxvirus strains associated with human infections.