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Aerial view of crowd connected by lines

Monkeypox: What We Know (and What We Don’t)

The longer and farther the virus spreads, the more likely it could become endemic in new areas, says UCLA epidemiologist Anne Rimoin.

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Andy Carstens

Andy Carstens is an intern at The Scientist. He has a bachelor's degree in chemical engineering from the Georgia Institute of Technology and a master's in science writing from Johns Hopkins University.

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Jun 24, 2022

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Update (July 25): The World Health Organization held a press conference on July 23 during which the organization’s director-general, Tedros Adhanom Ghebreyesus, declared that the monkeypox outbreak now constitutes a public health emergency of international concern. Despite the WHO’s advisory committee not reaching consensus on the matter when they met on July 21, Ghebreyesus says several of the criteria for declaring a global health emergency have been satisfied. Because there have now been 16,000 cases reported across 75 countries and territories, he says that the WHO’s assessment is that the risk of monkeypox is high in Europe but moderate elsewhere, adding that there is a “clear risk of further international spread.” Because the outbreak is currently localized in populations of men who have sex with men, especially those with multiple sexual partners, Ghebreyesus says there’s still a chance the outbreak can be stopped by working closely with the communities of men most affected and avoiding stigma and discrimination.

Update (June 27): The World Health Organization issued a statement Saturday (June 25) stating that the monkeypox outbreak does not yet constitute a “public health emergency of international concern.” While some on the advisory committee that made this recommendation held differing views, the group agreed by consensus not to assign monkeypox the global emergency label, which currently applies to the COVID-19 pandemic and polio eradication efforts, reports Reuters.

The current monkeypox outbreak started earlier this year with a few people in Europe and was unusual in that few cases involved travel to areas where the virus is endemic, such as in Western and Central Africa. Instead, most cases have been associated with sex between men. As cases continue to rise, evidence is emerging that monkeypox may have been spreading in the US for longer than health officials have known. Now, with thousands of confirmed cases in countries where the virus is not endemic, the World Health Organization is considering declaring monkeypox a global health emergency

To find out more about the monkeypox virus and the current outbreak, The Scientist spoke with Anne Rimoin, an epidemiologist at the University of California, Los Angeles. Rimoin has been studying monkeypox, a less-virulent relative of smallpox, in the Democratic Republic of the Congo (DRC) for two decades. In 2010, she coauthored a study showing that incidence rates there had been rising ever since smallpox vaccination campaigns had ceased.

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Anne Rimoin
Bader Howar

The Scientist: As of June 19, over 2,500 cases have been reported in more than 40 countries, with one death being reported. How seriously should the public be taking this monkeypox outbreak?

Anne Rimoin: I think that seeing this global distribution of cases of monkeypox suggests that it’s likely been spreading for a while undetected. And any time we see a virus spreading in populations that we don’t normally see it spread in or behaving differently than we anticipate it will behave, we should be taking it seriously.

TS: How does this outbreak compare to what typically occurs in areas of western and central Africa where the virus is endemic, in terms of parameters such as the number of cases and modes of transmission?

AR: We typically see [monkeypox] occurring—at least in DRC, which is where I work—in remote, rural settings, in people, the vast majority of [whom] have had contact with an animal that is likely the source of infection. That said, we’ve seen the number of human-human transmission events increase over time, and this is definitely something that that we should be keeping an eye on. But most of the work that’s being done in places like DRC [is] more about case identification than it is [about] case investigation and working through the epidemiology, just because of the limited resources that exist [there]. 

TS: Does the extent of the current outbreak suggest that monkeypox could become endemic in Europe and or the US?

AR: We’ve always known that as the population immunity to poxviruses wanes, we’re likely to see an increase in cases of monkeypox and other pox viruses. And that has already come to bear. We’ve seen more and more cases of pox viruses globally. One of the things that we’ve been traditionally concerned about has been whether monkeypox could indeed establish itself in human populations or in animal populations, and the longer that this virus continues to spread, the more likely that scenario is to occur.

TS: Does that mean that monkeypox spread would potentially look something more like COVID-19 in that it ends up circulating over a longer period of time, rather than an outbreak that ends?

AR: COVID is a very different kind of virus [in terms of spread] . . . [so] not at all in terms of the mechanisms. [Regarding this monkeypox outbreak], I don’t see any short-term end to this, [but] I don’t think anybody can predict that. This is, in large part, a choose your own adventure story, where we have to decide how seriously we’re going to take it, how badly we want to keep pox viruses out of circulation in human and animal populations outside of their endemic range, and if we’re willing to bear the consequences. So it depends.

This is, in large part, a choose your own adventure story, where we have to decide how seriously we’re going to take it.

TS: Are we doing the right things or, if not, what should we be doing?

AR: I don’t work for the department of health, I don’t work for the CDC, I don’t work for any of these organizations, so I can’t comment specifically on what we are doing.

What I would say is that the things that we need to do are pretty straightforward. We have to have case identification. We have to have case investigations. We need to have excellent contact tracing. We need to have good diagnostics in place. We need to be able to have materials out there so that clinicians know how to identify cases of monkeypox or suspected cases of monkeypox, how to collect samples, [and] exactly where they need to send the samples. [We need] a good system in place to handle those logistics. We need good materials out there for the public so that they can recognize if they may have been exposed to monkeypox . . . and exactly what to do if they think that they have a rash that fits the description. 

I think that we need to understand the epidemiology. We have to be very humble about what we know and what we don’t know—and remember that what we know about this virus is mostly from studies that were conducted in rural DRC, and then more recently . . . in Nigeria, but that’s only been since 2017. And all of this has been in under-resourced settings. We do know something about this virus; we have a base, but we have to understand the epidemiology in this new context and all the implications.

TS: The vast majority of cases in the current outbreak involve men who’ve recently had sex with other men, and the virus’s spread has been linked to social and sexual networks. Given that men having sex with other men is not new or uncommon, do scientists know why this outbreak is occurring now?

AR: So first of all, obviously, we don’t know exactly what happened. This is like we’re tuning into a TV series we’ve never seen before. We don’t know what episode we’re on. We know it’s not episode one. Is it two, is it five, is it ten? Are we in season two? We really don’t know where we are in all of this. And so there’s a lot of forensic epidemiology that we need to do to really understand it: looking more carefully at what’s happening [in endemic regions] is critical, [along with] places where we know it has been spreading . . . [and] using genetic sequencing data to have a better reconstruction of how long it’s been circulating. But it’s very possible that this has been going on for a while, we just haven’t been looking for it. 

This is like we’re tuning into a TV series we’ve never seen before. We don’t know what episode we’re on. We know it’s not episode one. Is it two, is it five, is it ten?

TS: Earlier you mentioned the actions that we need to take, but what main questions does the scientific community need to focus on answering to help control the spread of the current outbreak and to be better prepared for future outbreaks?

AR:  I think that the two key categories are characterizing the transmission mechanisms and [their] potential—so understanding routes for human-human transmission, assessing potential for presymptomatic and asymptomatic transmission, defining periods of infectivity, assessing the stability of virus on surfaces . . . and truly assessing the potential for reverse zoonosis and spillback events. And then the second category is characterizing clinical presentation and disease severity, [as well as] various risk groups. 

See “Predicting Future Zoonotic Disease Outbreaks

TS: Media outlets and public health agencies seem to be caught between not wanting to stigmatize gay and bisexual men by highlighting the fact that they’re most at risk in the current outbreak, while also needing to direct education toward that community. What advice would you give to media outlets covering monkeypox?

AR: I think we just have to make it clear that this virus is spread most efficiently—as we understand it—by close contact, and that includes sexual contact . . . in particular skin-to-skin contact [usually through contact with lesions, scabs, or respiratory secretions]. It also spreads through fomites. . . . Understanding that currently these are the sexual networks that it’s spreading in is important, but it’s [also] important for people to realize this has absolutely nothing to do with who is having sex with whom. It’s really important, across the board, that this should never be about stigmatizing a population. And I think that we need to double down on this point that this has nothing to do with who it’s infecting right now. It can affect anyone that is in close contact.

TS: What haven’t we discussed about the monkeypox virus or this outbreak that you think is important to mention?

AR: I think it’s really important to remind everybody that many of us who’ve been working in pox viruses have warned about the need to control [them] and really understand what’s happening on the ground. And if we want to be able to prevent global spread of pathogens, we have to work carefully to ensure that we have adequate disease surveillance, adequate mechanisms in place for countries where these kinds of viruses [are] circulating, [and the ability] to do the work that needs to be done. Otherwise, we’re constantly going to be playing catch up. But that’s going to require investment.

See “The Virus Hunter

Editor’s note: This interview has been edited for brevity.