https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4379562/
[snip] Smallpox was a severe human disease caused by the variola virus (VARV), which was both highly lethal and highly contagious [1,2,3,4,5,6]. VARV is a member of the genus Orthopoxvirus [4,5,6]. A characteristic feature of this virus is its strict specificity for humans. This viral pathogen circulated in the human population for many centuries and caused repeated large-scale epidemics with great numbers of both recovered and dead victims [3,7]. In the 18th century, smallpox was the cause of death of more than four hundred thousand people in Europe each year [3]. Fortunately, this particular virus was completely eliminated from the human community by the end of the last century due to vaccination [3,4,8].
The closest relatives of VARV, which are also pathogenic to humans, are the Old World orthopoxviruses, including the vaccinia (VACV), cowpox (CPXV), and monkeypox (MPXV) [5,6]. The major natural reservoir of the last two viruses is rodents. For a long time, the introduction of laboratory strains made it impossible to detect wild VACV in nature [3,4,9,10,11]. It is currently believed that VACV originated from the horsepox virus (HPXV) [12]. However, all these viruses that are closely related to VARV have broad ranges of sensitive hosts; correspondingly, it is of paramount importance to clarify the factors that enhanced the evolutionary specialization of the VARV ancestor towards its single host, humans. [/snip]
Somewhere I read it was thought to come from Camelpox. But that was any number of years ago.
2006 Apr-May;190(4-5):1093-8.
[The Antonine plague]
[Article in French]
Charles Haas
PMID: 17195627
Abstract: During the reign of Marcus Aurelius, the Roman Empire was struck by a long and destructive epidemic. It began in Mesopotamia in late AD 165 or early AD 166 during Verus’ Parthian campaign, and quickly spread to Rome. It lasted at least until the death of Marcus Aurelius in AD 180 and likely into the early part of Commodus’ reign. Its victims were “innumerable”. Galen had first-hand knowledge of the disease. He was in Rome when the plague reached the city in AD 166. He was also present during an outbreak among troops stationed at Aquileia during the winter of AD 168-169. His references to the plague are scattered and brief but enough information is available to firmly identify the plague as smallpox. His description of the exanthema is fairly typical of the smallpox rash, particularly in the hemorrhagic phase of the disease.
https://pubmed.ncbi.nlm.nih.gov/17195627/
Infez Med. 2009 Dec;17(4):261-75.
The Antonine Plague and the decline of the Roman Empire
[Article in Italian]
S Sabbatani 1, S Fiorino
Affiliations expand
PMID: 20046111
Free article
Abstract: The Antonine Plague, which flared up during the reign of Marcus Aurelius from 165 AD and continued under the rule of his son Commodus, played such a major role that the pathocenosis in the Ancient World was changed. The spread of the epidemic was favoured by the occurrence of two military episodes in which Marcus Aurelius himself took part: the Parthian War in Mesopotamia and the wars against the Marcomanni in northeastern Italy, in Noricum and in Pannonia. Accounts of the clinical features of the epidemic are scant and disjointed, with the main source being Galen, who witnessed the plague. Unfortunately, the great physician provides us with only a brief presentation of the disease, his aim being to supply therapeutic approaches, thus passing over the accurate description of the disease symptoms. Although the reports of some clinical cases treated by Galen lead us to think that the Antonine plague was caused by smallpox, palaeopathological confirmation is lacking. Some archaeological evidence (such as terracotta finds) from Italy might reinforce this opinion. In these finds, some details can be observed, suggesting the artist’s purpose to represent the classic smallpox pustules, typical signs of the disease. The extent of the epidemic has been extensively debated: the majority of authors agree that the impact of the plague was severe, influencing military conscription, the agricultural and urban economy, and depleting the coffers of the State. The Antonine plague affected ancient Roman traditions, also leaving a mark on artistic expression; a renewal of spirituality and religiousness was recorded. These events created the conditions for the spread of monotheistic religions, such as Mithraism and Christianity. This period, characterized by health, social and economic crises, paved the way for the entry into the Empire of neighbouring barbarian tribes and the recruitment of barbarian troops into the Roman army; these events particularly favoured the cultural and political growth of these populations. The Antonine Plague may well have created the conditions for the decline of the Roman Empire and, afterwards, for its fall in the West in the fifth century AD.
https://pubmed.ncbi.nlm.nih.gov/20046111/
McGill University
Office for Science and Society
Measles: the plague that ruined Rome
Ada McVean B.Sc. | 27 Jun 2018
Rome wasn’t built in a day, but from 165-180 CE, up to 2,000 of its citizens were killed per day.
The Antonine Plague, also known as the Plague of Galen (after the doctor who described it), decimated the Roman Empire. It was brought to Rome by armies returning from western Asia, causing fevers, skin sores, diarrhea and sore throats.
This plague, and the Plague of Cyprian that occurred about 70 years later, are generally thought to be due to smallpox and measles. The Roman citizens at this time would not had been exposed to either virus and thus would have had no immunity, which could explain the mass casualties seen (the first plague had a mortality rate of 25%).
While smallpox has not been seen clinically since 1977, measles still kills upwards of 85,000 people every year, despite being vaccine preventable. While the measles virus is most famous for causing the red rash that begins at the hairline and slowly spreads over the entire body, it can also cause fevers, sore throats, nausea and diarrhea. Perhaps just as distinctive, if not as noticeable, are the tiny white Koplik spots that may appear inside a victim’s mouth. The good news is that the rash actually signals the end of the viral infection, and the skin usually flakes off as the rash goes away.
Most of our readers are safe from the Romans’ fate, as measles was officially eliminated from the Americas in 2016. However, this elimination is conditional on travellers not bringing the virus back from their vacations and causing an outbreak. That’s why the MMR vaccine, which provides immunity against measles, mumps, and rubella, is recommended for all, travellers and home bodies alike.
In 2014 a group of unvaccinated Amish missionaries brought measles back from the Philippines. It rapidly spread through their largely unvaccinated communities, resulting in 383 cases of measles across 9 countries. Luckily, thanks to modern medicine, no one died. We’ve come a long way from the plague that wiped out one third of the Roman Empire, and thanks to vaccines, we’ve got no plans for a measles plague of our own.
https://www.mcgill.ca/oss/article/did-you-know-history/measles-plague-ruined-rome