Why monkeypox is nothing like Covid-19

Smallpox vaccines are effective against monkeypox. AFP, Reuters

It has been 30 months since the first news stories of a pneumonia outbreak in a market in Wuhan, China grew into what would become the Covid-19 pandemic. Now, we are hearing of a new virus in the headlines, monkeypox. And again, we are seeing maps of the globe peppered with ominous red dots. Each day, the dots swell with increasing case numbers, and new dots appear in countries that were previously unblemished, almost as if the globe itself has contracted an ominous rash.

This time, the first reports came out of the UK, and already there are over 1,200 confirmed cases in nearly 30 countries around the world. Understandably, people are worried.

So what is monkeypox? Are we seeing the beginning of another new pandemic? And how dangerous is this virus? If it keeps spreading, how bad could it get? To start, it is worth deciphering some strange and misleading names, and providing a bit of history.

Monkeypox is a poxvirus – unlike, say, the chickenpox virus, which is not actually a poxvirus. But it does share one feature with chickenpox – neither usually circulates in the animals for which they are named. The natural hosts for monkeypox are rodents.

What is concerning is that monkeypox is related to another very deadly poxvirus: smallpox – also known as the variola virus. Smallpox was the very first virus ever to be eradicated by a vaccine, which in this case came in the form of a naturally occurring virus, vaccinia. The vaccinia virus is a cousin of smallpox whose natural hosts were likely some sort of ungulates (hoofed animals, such as horses and cows). Vaccinia wasn’t nearly as dangerous to humans as smallpox, and because of its relatedness to variola, when people were inoculated with vaccinia, the “lessons” their immune systems learned from being infected afforded lifelong immunity to smallpox.

In just the same way, we already know that vaccinia and related smallpox vaccines also provide cross-protection against monkeypox. Therefore, those who have been reading closely will already have noticed important distinctions from the Covid-19 situation, which should help to assuage any incipient panic.

First, we already have effective vaccines against monkeypox (smallpox vaccines). Secondly, unlike Covid-19, the immunity one gets from a smallpox vaccine will protect from monkeypox for life. Fortunately, even though smallpox has been extinct since 1977, governments around the world have long worried that it might be used as a bioweapon. So they have continued to manufacture and stockpile vaccines, and there has been continued investment in antiviral drugs. For example, tecovirimat, an antiviral drug against smallpox that was approved by the US Food and Drug Administration in 2018, is effective against monkeypox.

Moreover, we also almost certainly do not have to worry about monkeypox variants. Poxviruses are DNA viruses, with large genomes made up of double-stranded DNA, just like our own. DNA viruses mutate much more slowly than RNA viruses, so the risk that new monkeypox variants will rapidly emerge is virtually nil.

How does monkeypox spread? Although monkeypox can theoretically spread by air or by contact, the virus has thus far spread almost entirely among men through sexual contact, which strongly implies that close, physically intimate contact is the main route of transmission.

Monkeypox itself is endemic in west and central Africa, and there have long been sporadic human infections in countries such as Nigeria, the Democratic Republic of Congo and Cameroon. And it is important to remember this is not the first time that the virus has spread internationally. For instance, there was an outbreak in the US in 2003 in which 71 people caught the virus. Comfortingly, that outbreak was later fully contained.

As for the danger factor, although the Central African clade of monkeypox is lethal in about 10 per cent of cases, the so-called“West African clade”, which is the variety driving the current outbreak, is much less dangerous, causing death in about 1 per cent of cases. Fortunately, there have not been any recorded deaths in this outbreak so far.

Given that this outbreak started with just three cases announced by the UK in early May, and one month later there are already well over 1,000 cases globally, it might appear that the situation is spiralling out-of-control. But much of what looks like very “rapid” growth in case numbers reflects improved surveillance. Health professionals around the world are looking for cases and finding them. This outbreak has been going on at least since November 2021, when a case was identified in the US state of Maryland in a traveler returning from Nigeria.

Monkeypox takes much longer than a coronavirus to establish itself in a new host, and people infected with monkeypox cannot spread the infection until at least about 7 days after contracting the virus. This means that public health workers should be able to use a strategy called “ring vaccination” to vaccinate any close contacts of a confirmed case, thereby preventing uncontrolled spread of the virus.

The real concern here is that monkeypox will establish itself in rodent populations outside of its current “enzootic” (endemic) range in Africa. If this happens, then we would expect to continue to see sporadic outbreaks of monkeypox until everyone is vaccinated against smallpox. Because routine vaccination against smallpox was halted in most parts of the world in the 1970s after the disease was eradicated, many more of us are susceptible to monkeypox.

The key takeaway is that the world needs to continue to keep its eyes on this virus and do its best to avoid stigmatising those who come forward and test positive. Only by bringing the virus into the light can we recognise and control it.