While the World Health Organization recently declared a global public health emergency for a more contagious type of mpox, formerly called monkeypox, the spread of another type that first emerged in North Carolina in 2022 has been relatively contained.
Since the outbreak in 2022, the state health department says there have been nearly 800 documented cases, but just 44 in the last six months, and only one in August.
WUNC's Will Michaels spoke with Dr. William Fischer, director of emerging pathogens at the Institute for Global Health and Infectious Diseases at UNC-Chapel Hill, about the differences between the two types of mpox and how to mitigate the spread of the one that’s already here.
This conversation has been edited for clarity and brevity.
There are two types of mpox circulating, Clade I and Clade II. The one that is the subject of the current global public health emergency has not been detected in the U.S., but what do we know about each one and how they spread?
The virus that causes mpox, as you mentioned, really falls into two major groups of viruses: one that has traditionally been found predominantly within countries in Central Africa, and that is what we refer to as Clade I, and then a second clade, which is traditionally found in countries in West Africa, which is now known as Clade II virus. And, now what we're seeing is really an unprecedented increase in the numbers of Clade I infections, both within countries of Central Africa, but we're also starting to see it spread beyond those countries where we traditionally see it.
Who is most at risk of infection?
In the global outbreak that we saw with Clade II virus in 2022 and which still continues today, we've seen that over 90% of infections have occurred in men, and largely men who have sex with men. Clade I virus, we have seen both sexual transmission and and nonsexual transmission as well.
I often get asked, "Am I at risk if I go to the gym or if I go to the grocery store, if I go clothes shopping?" And the reality is probably not. Transmission really requires very close contact. I think there are steps that we can take and behavioral changes that we can make to prevent ongoing transmission.
One of the most effective prevention strategies includes vaccination. And, in fact, we have a vaccine. Unfortunately, only about 23% of the people who are currently eligible for that vaccine have been vaccinated. And, I think this highlights a really important missed opportunity to prevent transmission of this virus. The CDC currently recommends this vaccine for gay, bisexual and other men who have sex with men and who are also vulnerable to mpox exposure.
TPOXX (tecovirimat) is a drug that has been stockpiled to treat smallpox should there be a reemergence. What do we know about its potential to treat mpox?
One randomized clinical trial was recently completed in the Democratic Republic of Congo and really led by a remarkable group. Now they've just recently released their top line results, and unfortunately, they found that tecovirimat did not accelerate time to lesion resolution in that patient population that was largely Clade I disease.
We did learn two things I think are really important. Number one is that with really good supportive care, we can reduce the mortality rate associated with Clade I disease. They dropped their mortality rate from about 3.6% to about 1.7% and that's something that we can do here right now, is really work to improve that good supportive care. Number two is that we learned that tecovirimat is safe.
I think it's going to be really important to complete these other clinical trials of tecovirimat, because it's slightly a different patient population. It's looking mostly at in Clade II disease. So I think it'll be important to try to identify whether it's effective in this disease or not.
