Abstract
The orthopoxviruses (OPV) comprise several emerging viruses with great importance to human and veterinary medicine, including vaccinia virus (VACV), which causes outbreaks of bovine vaccinia (BV) in South America. Historically, VACV is the most comprehensively studied virus, however, its origin and natural hosts remain unknown. VACV was the primary component of the smallpox vaccine, largely used during the smallpox eradication campaign. After smallpox was declared eradicated, the vaccination that conferred immunity to OPV was discontinued, favoring a new contingent of susceptible individuals to OPV. VACV infections occur naturally after direct contact with infected dairy cattle, in recently vaccinated individuals, or through alternative routes of exposure. In Brazil, VACV outbreaks are frequently reported in rural areas, affecting mainly farm animals and humans. Recent studies have shown the role of wildlife in the VACV transmission chain, exploring the role of wild rodents as reservoirs that facilitate VACV spread throughout rural areas. Furthermore, VACV circulation in urban environments and the significance of this with respect to public health, have also been explored. In this review, we discuss the history, epidemiological, ecological and clinical aspects of natural VACV infections in Brazil, also highlighting alternative routes of VACV transmission, the factors involved in susceptibility to infection, and the natural history of the disease in humans and animals, and the potential for dissemination to urban environments.
Highlights
The Poxviridae family is comprised of large DNA viruses, capable of infecting a variety of organisms
Data presented by Miranda and colleagues reinforce the findings proposed by Abrahão et al, who proposed an ecological model to explain how the rodents could act as a link for vaccinia virus (VACV) spread between wild and anthropic environments [56]
Since the isolation of the first presumably zoonotic VACV isolates in Brazil, two controversial hypotheses have arisen relating to bovine vaccinia (BV) outbreaks and the origin of VACV [15,17,75,78]
Summary
The Poxviridae family is comprised of large DNA viruses, capable of infecting a variety of organisms It is divided into two subfamilies: the Entomopoxvirinae, which are invertebrate viruses, and the Chordopoxvirinae, which are those that infect vertebrates. In May 1980, smallpox was declared eradicated due to a herculean effort promoted by the World Health Organization (WHO), which established the global smallpox eradication program. This conquest only became possible due to the worldwide distribution of a live vaccine composed of a related virus from the OPV genus, the vaccinia virus (VACV) [1,3,4,6,7,8]. Despite being an extremely well-studied virus, its origin and natural history remain poorly understood [4]
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