I’ve never seen monkeypox in my 30-plus year career. That’s because it is a rare disease in the UK. When there have been cases in this country (there was a cluster in 2018) they were associated with travel to Nigeria, where the disease is endemic. So it is certainly noteworthy that we are seeing cases in several countries, including the UK, Portugal, Spain, Canada and the US.
What are the symptoms of monkeypox?
The disease is caused by an orthopoxvirus in the same family as smallpox and cowpox. It was first identified in monkeys in Africa in the late 1950s, and the first transmission to humans was recorded in the 1970s. There are two versions, or clades: the West African and the Congo Basin clades. The West African clade, which has been responsible for all UK cases to date, generally causes a self-limiting illness with a low mortality, comparable with Covid. Affected individuals will, after an incubation period of up to three weeks, develop a flu-like syndrome with fever, muscle aches and gland swelling. After a few days a rash evolves with tiny blisters called vesicles, typically starting on the head and spreading down the body. Just like chickenpox, these can leave scars once healed.
How is it transmitted?
Monkeypox has traditionally been regarded as having low transmissibility, thought to require very close personal contact to be passed on – however, that view might need revision. The smallpox vaccine protects against monkeypox as well, and up until the late 1970s most people globally were immunised as part of the successful eradication campaign that saw the smallpox virus eliminated in 1980. However, over the past five years or so, monkeypox has become more prevalent in Africa, thought to be because younger age groups no longer had protection (smallpox vaccination having long since ceased). Additionally, immunity in older people has probably waned over time. These factors might enable the current outbreak to be spread more readily here.
The fact that cases are arising in various, unconnected locations suggests that community transmission is occurring, and probably has been for some time. Being rare in the affected countries, and being generally mild, earlier cases may well have been misdiagnosed. A critical unknown at present is what transmissibility proves to be like: if it’s low, then outbreaks should be readily controlled, but if – either by virtue of waning smallpox immunity, or due to the virus having acquired enhanced infectivity – it’s higher than estimated, it may be harder to contain.
How serious is it?
If we do see widespread cases, should we be worried? Although an infection with a 1 per cent mortality is generally considered mild, if large numbers of people become affected, then the absolute numbers with serious disease could become significant. Added to this, the Covid pandemic revealed quite how many in our population are, by virtue of co-morbidities or medical treatment, immunocompromised and therefore more vulnerable to infection.
Covid has posed a particular challenge because of its capacity to cause serious respiratory disease and blood clotting problems. Early waves saw a significant percentage of patients require hospitalisation, which threatened to overwhelm the health service prior to widespread vaccination. Monkeypox does not have this capacity.
But coming hard on the heels of Covid, and with the recent outbreak of serious hepatitis in children of an as yet unknown causation, the appearance of monkeypox is bound to cause a degree of public consternation. The facts, as known currently, would suggest this latest viral outbreak should not pose us a significant problem. We should gain a fuller picture over the coming weeks, but a WHO advisory panel last week decided against labelling monkeypox a public health emergency of international concern.
Intriguingly, one of the theories regarding the outbreak of hepatitis in children is that Covid could be acting as a co-factor, rendering a usually benign adenovirus capable of causing much more significant disease in some individuals. Whether Covid proves to be a facilitator for monkeypox should be another area of active investigation.
This article was originally published on 20th May.
[See also: Monkeypox is not a gay virus. Haven’t we been here before?]