Paleovirology of monkeypox virus: Egyptian animal mummies should be in focus

We read with interest a recent Correspondence published in The Lancet Microbe,¹ which postulates the possible existence of monkeypox in ancient Egypt. Although the idea of the paper is valid and has been previously discussed,² some points mentioned might be confusing, and some related important issues were not mentioned.

Although the world has long been fascinated by human mummies, interest in animal mummies has only recently increased. Ancient Egyptian animal mummies are less well researched than human mummies, but once well studied, could open the door to understanding epidemic dynamics at the human–animal interface in ancient times and the subsequent impact on modern diseases.

The preservation of the body was paramount for the ancient Egyptians, and animals held such a prominent place in ancient Egyptian society that tens of millions were mummified. Pet animals, including dogs, cats, monkeys, and gazelles, were elaborately mummified and frequently given separate coffins.

Unlike monkeypox, the smallpox virus is an exclusively human pathogen and does not infect animals. Considering mummified animals in paleovirology, as previously suggested,2, 3 could give us a chance to track the history of zoonotic diseases.

African rope squirrels (Funisciurus sp) have been identified as a potential source of monkeypox virus transmission to people and other animals in monkeypox-endemic areas.⁴ In the same context, Tiee and colleagues⁵ successfully isolated Congo Basin monkeypox virus from skin samples (93 of 1038) of five species of African rope squirrel collected across central Africa dated 1899.

Besides ancient writings, infectious diseases among the ancient Egyptians are identified in mummies mostly by detecting pathogens or by the presence of specific or pathognomonic lesions (such as smallpox). However, the presence of pathogens does not definitely mean an active disease. To the best of our knowledge, no evidence exists of cholera, measles, or influenza in ancient Egypt; therefore, we need to know the evidence behind the authors' claim that these diseases were very common in ancient Egypt.

Based on paleogenetics, it is feasible to gather important information on monkeypox evolution by studying ancient animal mummies, using modern tools such as molecular clock techniques, Bayesian molecular-clock analysis, ancient DNA extraction, PCR amplification, and Sanger sequencing.

To our knowledge, there is no evidence that the variola virus is one of the most common organisms found in Egyptian mummies, as the authors mentioned. Additionally, in our opinion, the postulation that asymptomatic monkeypox infection could complicate linking monkeypox back to Egyptian history does not make sense, because Tiee and colleagues⁵ noted no obvious skin lesions during sample collection. Tiee and colleagues' findings, as well as findings from Hutson and colleagues,⁶ also prove that skin could be used as a reliable tissue for monkeypox virus DNA detection.

Analysis of historical specimens of Egyptian animal mummies could reveal information regarding previous viral changes as well as probable reservoirs and intermediate hosts of monkeypox virus, and can extend to encompass other zoonotic pathogens.

We declare no competing interests.