The World Health Organization recently declared the spread of mpox in multiple African countries a public health emergency of international concern. On Aug. 15, the first case outside of Africa of the concerning mpox strain was reported involving a traveler from Sweden who had returned from Africa. And on Aug. 22, health officials confirmed a second case in Thailand.
Two versions of the mpox virus have been circulating globally.
- One is the strain called clade IIb, which caused the big international outbreak in 2022, and was almost exclusively sexually transmitted. The population affected was predominantly men who have sex with men. These cases have declined, but they’ve never gone down to zero. Some small clusters of cases are still seen in New York.
- The other is a newer version, known as clade Ib, that’s spread from person to person. This newer strain is causing an outbreak in the eastern part of the Democratic Republic of the Congo. It has also spread outside of Africa. This is the one that triggered the WHO’s declaration of a public health emergency.
We spoke with Dr. Eric A. Meyerowitz, an infectious disease expert at Montefiore Medical Group, to ask what else New Yorkers should know. The interview was condensed and lightly edited for clarity.
Epicenter NYC: What makes this clade I mpox outbreak more concerning than the clade II?
Dr. Meyerowitz: What seems to be different about clade I is that initially, there were reports of higher mortality rates. The mortality rate for clade II, fortunately, was extremely low, far less than 1%. For clade I, there were ranges of reports from 1% to 10%.
Now, the National Institutes of Health (NIH) co-sponsored a study of an antiviral called TPOXX used off-label for mpox during the global outbreak. The mortality rate in that trial was 1.7%, which is actually far lower than those maximum rates of about 10%.
So that’s one concern — potentially there’s a difference in the severity of cases based on mortality, although the results from this study suggest that it’s much less than 10% mortality overall.
The second major concern is the difference in who’s affected — possible different transmission routes, so this might be more transmissible. What was being seen and described in the Democratic Republic of Congo is some household transmission. It still appears to be predominantly sexual transmission and there’s definitely documented heterosexual transmission, more so, to date, with clade I than there had been with clade II.
But then also the sense that there is more household transmission. Fortunately, with our clade II cases, we saw essentially zero household transmission. Almost none of our patients — none that I can think of — had household contacts who developed infection. That’s one of the other concerns that people are worried about with this new clade.
And in the 2022 outbreak, we did not see infections in very many children. Now, most of the deaths that are happening with clade I infection have been in adolescents and young children.
Epicenter NYC: Could you talk about who is susceptible to mpox the way we’re currently seeing it in the U.S., and anything that the community should know about?
Dr. Meyerowitz: One of the primary risk factors for mpox, especially clade II, is being a man who has sex with men. Again, almost all of the transmission has been sexual transmission, predominantly in that population. A lot of that population also has HIV, and what’s been seen in other studies is that people with advanced or untreated HIV are more susceptible. So some people who have had HIV for years but weren’t aware of it or were not getting treated ended up having worse outcomes. It also suggests that this could be the case with the clade I virus as well.
Dr. Meyerowitz: Certainly. For clade II, there were some outbreaks in congregate settings, particularly jails and prisons, but that was more related to the sexual transmission among people who were having sex in those settings. One of the main fears around clade I is that if it does prove to be more transmissible in these other ways, then yes, it could affect those groups. That’s one of the other things that really needs to be assessed and tracked.
Epicenter NYC: Are there certain common misconceptions about mpox that you think New Yorkers should be aware of?
Dr. Eric Meyerowitz: One is that people can have rashes for many different reasons. Early in 2022, there were instances where people were taking pictures of others on trains and posting them to social media. That is really not helpful or appropriate because there are all sorts of different explanations for rashes.
The second thing is, even with what seems to be a more transmissible clade, we expect the transmissibility to be relatively similar. So, I think keeping things in perspective is really important and not jumping to conclusions or sending out alarmist messages before having more information.
The third thing is, it can be easy to think, “I need an mpox vaccine right now,” when your risk is actually extremely low or close to zero. An important point: healthcare workers are still, in general, not recommended to get the mpox vaccine. Those of us who’ve been taking care of hundreds of mpox patients have not received mpox vaccines because the risk of healthcare transmission is considered to be so low.
While we need to keep an eye on these things, the key to curbing this sort of outbreak is to get the vaccine to where it’s needed and focus on getting resources there, so that good transmission studies and other studies about possible treatments can be conducted.
Epicenter NYC: How treatable is this right now?
Dr. Eric Meyerowitz: There appears to be no effective antiviral at this time, but we can effectively manage the symptoms—mainly pain and discomfort. People should not be suffering if this is something they are experiencing.
Another thing is that it really is quite a spectrum of severity. Some people, fortunately, don’t have very severe symptoms. With all the immunity we have accumulated in this country from the vaccine program and the extensive natural infection from clade ll infection, that will hopefully provide extensive protection against this other clade as well if it does happen to spread further.
Epicenter NYC: So how concerned would you say New Yorkers should be about a potential outbreak of clade l in New York?
Dr. Eric Meyerowitz: Based on the extensive outbreak of clade ll infection in 2022, I don’t think we’re likely to have a significant outbreak of clade l infection. At the same time, it still is very early, so we need more information to see what happens.
The key is what will happen over the next few weeks in terms of how many more cases and how many more countries are affected. We will likely see some travel-imported cases of clade l, and the hope is that with testing and isolation available, those will remain isolated, and people will get the support and care they need, preventing significant outbreaks.
Epicenter NYC: Why don’t you think there would be a significant outbreak based on the 2022 outbreak?
Dr. Eric Meyerowitz: There is extensive baseline immunity in New York among these high-risk populations, both from prior infection and from the vaccine.
If you’re concerned about mpox and have had a potential exposure, Dr. Meyerowitz recommends you see your physician for a diagnosis or to check if you’re a possible candidate for the mpox vaccine.
Read more of Epicenter NYC’s health coverage, and award-winning engagement work around mpox, here.
