Mpox: How deadly is the virus and what treatments are available?

Mpox, formerly known as monkey poxis driving the ongoing outbreak in the Democratic Republic of Congo (DRC) and neighboring countries. The rise in cases is partly due to a new variant that is thought to be deadlier than the version of the virus that caused the global mpox outbreak in 2022. But there are treatments that can help.

How deadly is mpox?

Studies show that the death rate among people infected with the Impox strain that is driving the ongoing outbreak ranges from 1 to 11 percentThe differences in reported death rates are likely due to differences in the populations that become ill and problems with disease surveillance, says Lilith Whittles at Imperial College London.

For example, infants and children, whose immune systems are weaker, may be more likely to develop severe — and potentially fatal — infections than adults. And people with suppressed immune systems, such as those with HIV, are also more vulnerable, she says.

What’s more, in some regions, people have limited access to health care, and thus limited surveillance for mpox. As a result, only the most severe cases end up being detected in health clinics, while milder cases are missed, making death rates appear higher than they actually are. More frequent misdiagnosis of mpox symptoms as other diseases, such as measles or chickenpox, also leaves more cases undetected, Whittles says.

When people die from mpox, it's from complications like sepsis, when the infection gets into the bloodstream and causes organ failure, or from lung damage due to inflammation caused by the mpox virus, he says. Piero Olliaro at Oxford University.

What treatments for mpox do we have?

In the DRC and neighboring countries at the center of the current outbreak, treatments specifically for mpox are largely unavailable. Instead, doctors focus on treating symptoms, which typically last two to four weeks. This includes relieving fever and headaches with paracetamol (acetaminophen) or cleaning skin lesions to prevent bacterial infections, says Jean Claude Udahemuka at the University of Rwanda.

Elsewhere, in the UK and US, doctors can use the antiviral drug tecovirimat to treat people with severe forms of mpox. Originally developed to treat smallpox, its use against mpox is based on animal studies in which it improved survival rates compared with placebo. Tecovirimat works by binding to a protein found on the surface of both mpox and smallpox that the viruses use to free yourself from an infected cell and spread to other cells.

Doctors in the US and UK may also treat mpox with other antiviral drugs, such as cidofovir, which has been shown to protect mice from lethal doses mpox virus. This drug blocks the enzyme that the virus uses to replicate its genome.

And another treatment, known as VIGIV, involves injecting smallpox antibodies from people who have been vaccinated against smallpox into those infected with mpox. This boosts the immune response against the viruses.

How effective is MPox treatment in humans?

While animal studies suggest these treatments work against mpox, their effectiveness in humans is unknown. Initial results from a recent randomized controlled trial—the best type of medical evidence—in the DRC suggest that tecovirimat does not speed up healing of painful lesions in children and adults infected with the I mpox strain.

Even so, the researchers found that the mpox death rate among participants who received the antiviral drug was 1.7%, an improvement over the typical 3.6% death rate in the DRC. However, that could be partly explained by the fact that the participants included in the study were closely monitored in the hospital, Olliaro says.

Ultimately, more effective treatment and a better understanding of how deadly mpox can be will be critical to protecting people, particularly in the DRC, from the ongoing outbreak, he says. Lucille Bloomberg at the University of Pretoria in South Africa. “There’s a lot of work to do,” she says.