Mpox: What is the fatality rate of this virus and what treatment is there?

Mpox, formerly known as monkeypox, continues to cause an outbreak in the Democratic Republic of Congo (DRC) and neighboring countries, with the surge in cases being blamed in part on a new variant that is thought to be more deadly than the Mpox virus variant that caused a global outbreak in 2022. But there are treatments that may help.

How deadly is MPOX?

Studies have shown that the case-fatality rate for people infected with the MPOX lineage I variant that is driving the current epidemic ranges from about 1 to 11 percent. The variation in reported case-fatality rates is probably due to differences in affected populations and problems with disease surveillance, says Lilith Whittles of Imperial College London.

For example, infants and children with underdeveloped immune systems may be more likely than adults to develop serious, even fatal, infections, and people with suppressed immune systems, such as those with HIV, may also be more susceptible, she says.

Additionally, some areas have little access to health care and limited surveillance for MPOX. As a result, health care providers only catch the most severe cases and miss milder ones, making the death rate appear higher than it actually is. If MPOX symptoms are increasingly misdiagnosed as other illnesses, like measles or chickenpox, more cases will go undetected, Whittles says.

Piero Oriaro of the University of Oxford said that when people die from MPOX, it is because of complications such as sepsis, when infection enters the bloodstream and causes organ failure, or from lung damage caused by inflammation caused by the MPOX virus.

What are the MPOX treatment options?

In the Democratic Republic of Congo, where the outbreak is at its epicenter, and neighboring countries, few medications are available that specifically treat MPOX. Instead, doctors focus on treating symptoms, which usually last two to four weeks. That can include relieving fever and headaches with paracetamol (acetaminophen) and cleaning skin lesions to prevent bacterial infection, says Jean-Claude Udahemuka of the University of Rwanda.

In the UK and US, doctors can use the antiviral drug Tecovirimat to treat people with severe MPO. Originally developed to treat smallpox, the drug was used for MPO after animal studies showed improved survival rates compared to placebo. Tecovirimat works by binding to a protein on the surface of both MPO and smallpox. This protein is used by the virus to release itself from infected cells and spread to other cells.

Doctors in the US and UK can also treat MPOX with other antiviral drugs, such as cidofovir, which has been shown to protect mice from lethal doses of the MPOX virus. The drug blocks an enzyme the virus uses to replicate its genome.

Another treatment, known as VIGIV, involves injecting people with smallpox with antibodies against smallpox taken from people who have had the smallpox vaccine, thus strengthening their immune response to the virus.

How effective is mpox treatment in humans?

Animal studies suggest that these treatments may be effective against MPOX, but their effectiveness in humans is unknown. Early results from a recent randomized controlled trial in the Democratic Republic of Congo (the best medical evidence) show that tecovirimat does not speed up the healing of painful lesions in children and adults infected with the lineage I variant of MPOX.

Nonetheless, the researchers found that the MPOX mortality rate for participants who received the antiviral drug was 1.7 percent, an improvement over the 3.6 percent mortality rate typically seen in the Democratic Republic of Congo. But this can be partly explained by the fact that participants in the trial received close care in hospital, Oriaro says.

Ultimately, better treatments and a better understanding of MPOX’s lethality will be essential to protect people, particularly those in the Democratic Republic of Congo, from the ongoing epidemic, says Lucille Blumberg of the University of Pretoria in South Africa. “There’s a lot of work to be done,” she says.