Monkeypox: Smallpox's Mild Little Brother
"Smallpox eradication, coordinated by the WHO and certified 40 years ago, led to the cessation of routine smallpox vaccination in most countries. It is estimated that over 70% of the world’s population is no longer protected against smallpox, and through cross-immunity, to closely related orthopox viruses such as monkeypox. Monkeypox is now a re-emerging disease." (Simpson et al., 2020, p. 5077)
Prairie dogs
2006 photo by Brocken Inaglory of "kissing" prairie dogs, which can be a carrier for monkeypox
Smallpox may have been eradicated in 1971, but many of its evolutionary relatives-- belonging to a genus of viruses called Orthopoxvirus-- continue to occur in the world. Cowpox, well-known for being the virus Edward Jenner used to develop the smallpox vaccine, can still be found in Europe. Of greater interest to epidemiologists, however, is a relatively new orthopoxvirus known as monkeypox. Danish scientists were the first to identify and isolate monkeypox when in 1958 they observed an outbreak of a smallpox-like disease among a colony of laboratory macaques (a genus of highly social Old World monkeys) imported from Singapore. Monkeypox was first seen in humans in the Democratic Republic of the Congo (DRC) in 1970, and while most future outbreaks have been concentrated in central and west Africa, the disease has occasionally spread further afield. In 2003, there was a monkeypox outbreak in the American Midwest resulting in 37 confirmed and 10 probable cases, believed to have been caused by a shipment of infected rodents from Ghana housed next to a group of prairie dogs later sold as pets. Fortunately, the disease remains fairly rare and has a lower mortality rate than smallpox, at about 5-6%. The mortality rate is even lower, below 2%, if one excludes immunocompromised people with AIDS from the calculations.
Following the eradication of smallpox, epidemiologists have worried that monkeypox could emerge to fill the ecological niche once occupied by smallpox. Concerns ran particularly high in 2007 when there was a twenty-fold spike in infections in the DRC; however, monkeypox has not become the monumental threat smallpox was. While monkeypox remains endemic in the DRC, with up to 1,000 cases each year, the disease has not taken root elsewhere. Besides the DRC, only Nigeria continues to regularly deal with monkeypox, and the disease is more controlled there, with only 176 cases recorded as of 2019. Beyond standard recommendations of good hygiene and quarantine (which can sometimes be difficult to enforce with monkeypox patients because they often feel fine and wish to return to their normal lives), monkeypox prevention has seen the return of smallpox vaccination. When a Nigerian visiting Singapore on a business trip developed skin lesions after his arrival, tens of close contacts were given a smallpox vaccine to halt the potential spread of monkeypox.
Although it was swiftly and effectively controlled, the Singaporean outbreak illustrates why epidemiologists worry about monkeypox. With global travel making the world more interconnected, there is potential for rare, localized diseases to spread widely. The emergence of other new orthopoxviruses--namely, the Akhmeta virus in the Georgian Caucasus and the Alaskapox virus in the United States-- has added extra urgency onto research into smallpox's genetic relatives.