The first thing you need to know about monkeypox is that it’s probably NOT spread by monkeys. I say probably because no one actually knows the animal reservoir, although rodents are highly suspect. The reason it is called Monkeypox is that the virus causing the disease was first isolated in laboratory monkeys in 1958. It was mostly of academic interest until the first human case was confirmed in 1970, in a 9-year-old boy from previous Zaire. Since then, most human cases were reported in only 10 countries located on the western and central African continent. It is considered a zoonotic disease (spread from an animal vector to humans) with the only inter-human transmissions documented having occurred from very close and prolonged contact. The largest human outbreak recorded has been less than 200 suspected cases. Remember in a previous blog posting (5 August 2020), I mentioned that the term spillover refers to the moment a zoonotic virus passes to a human that then passes the virus to another human. The term is important because today we are witnesses to a spillover event.
The monkeypox virus is an MPXV virus, a member of the genus Orthopoxvirus within the family poxviridae. Other orthopoxviruses that cause infections in humans include variola (smallpox), vaccinia (smallpox vaccine), and cowpox. Symptoms of monkeypox infection include fever, rash, respiratory symptoms, and lymphadenopathy.
When I was in medical school, MPXV was generally considered an exotic virus. As a pediatrician, I was intrigued by an American outbreak of monkeypox in 2003 because many of the cases were in children. But the numbers in that outbreak were very small (around 40 confirmed, ~80 suspected) and all cases were due to contact to MPXV infected prairie dogs bought as pets. (The prairie dogs were infected by being housed in close proximity to infected rodents imported from Ghana to Texas.) There were zero human-to-human transmissions and zero fatalities. In July and November 2021, two travelers independently carried the virus to the United States from Nigeria. Those have been the only reported cases in the US…. until the last few days.
In 2010, a report in the Proceedings of the National Academy of Sciences reported a major increase in human monkeypox incidence 30 years after smallpox vaccination campaigns ceased in the Congo. Why is that? Because smallpox vaccinations give almost 85% protection for monkeypox. But remember that WHO declared the world free of smallpox on May 8, 1980, and global efforts at vaccination ceased. I, personally, was revaccinated with the smallpox vaccine after 9/11, when the US government became more concerned about smallpox being utilized as biological warfare. Alabama wanted physicians vaccinated and ready to respond in the event of a terror event.
Today, we are witnessing a spillover event. This week, WHO reported over 80 cases of monkeypox in 11 different countries. In the UK alone, the first case was identified on May 7th and has since doubled. The US has reported a case in Massachusetts. What is especially notable about these cases is the absence of association with an animal vector. That leaves the very real possibility of inter-human transmission AND a change in the transmissibility pattern of an old virus. Does that sound familiar? It should. I remember my first reaction as Covid started spreading was, how can this be? It’s a coronavirus.
I don’t think people should be alarmed. For one thing, as awful as the photos of infected people may look, the pustular rash is actually a good thing. Unlike the 40% of infected Covid patients who had no symptoms but were communicable, it will be easy to contact trace because of the rash. Secondly, we have a vaccine effective against this virus. Thirdly, we do have antiviral meds that can ameliorate symptoms. Fourthly, the disease seems to be self-limited. Human cases in rural central and western Africa, where medical resources are limited, have a mortality of 1-10%.
At this moment, I am not alarmed about the possibility of a pandemic. But I am intrigued (intellectually speaking) by bearing witness to a spillover event. I think there is a very real possibility that we will see a large increase in cases in the near future.
Buckle up – let’s see if the world has learned anything at all about public health from the Covid pandemic. Pardon me if I am ambivalent about what we may have learned. My brain has still not been able to cope with the idea of 1 million American deaths, 700,000 of which occurred AFTER the development of a vaccine.
Judy Gattis says
We’ll done, Diana. I appreciate the info. We’ll get together after we return from D.C.
Charles Gattis says
Really good information. Thanks for posting.