The World Health Organization has labeled a surge in cases of mpox in a number of African countries a public health emergency — shining a spotlight on the disease, which previously attracted international attention during a global outbreak in 2022.
The virus was first detected in humans more than 50 years ago in the Democratic Republic of Congo and has been considered endemic there for decades. A new form of the virus, known as clade 1b, is now spreading rapidly in eastern parts of the country, as well as in neighboring countries that have not previously been affected.
Here’s what to know.
What is mpox?
Mpox is a zoonotic virus that causes flu-like symptoms and a rash with painful lesions. World health officials no longer use the term “monkeypox,” as it was previously known, because it is inaccurate (scientists now believe the virus originates in rodents) and is stigmatizing by associating a disease disproportionately affecting Black people with a slur used against them.
The WHO previously declared mpox an international health emergency in 2022 amid an outbreak that affected mostly gay and bisexual men across the globe, with nearly 100,000 cases and 208 deaths in 116 countries. Cases in that outbreak plunged after a campaign to deliver vaccines, but the virus has persisted in parts of Africa where the virus has been endemic and vaccines are not available.
This year, it was reported for the first time in some African countries including Kenya, Rwanda and Uganda — an “especially concerning” development that was “one of the main reasons” for the WHO’s Wednesday decision to again declare mpox a public health emergency of international concern.
What is the mortality rate for mpox?
According to the European Center for Disease Prevention and Control (ECDC), mortality rates of mpox vary across outbreaks. Children and people with vulnerable immune systems, including those with untreated HIV, are most at risk of severe disease and symptoms.
So far this year, more than 15,600 cases and 537 deaths have been reported in Congo – exceeding last year’s total, the WHO said.
Experts say the clade 1 virus, which has long been endemic in Congo, and its offshoot clade 1b, which emerged last year, typically cause more-severe illness than the clade 2 viruses that drove the 2022 global outbreak.
The death rate is about 5.5% in the Congo province where clade 1 predominates, according to the U.S. Centers for Disease Control and Prevention. The death rate for clade 1b outbreaks have been lower – fewer than 1 percent of infected people.
Experts caution against comparing fatality rates because the differences could be explained by who is becoming infected rather than the type of virus. The higher death rate for clade 1 could be explained by the outbreak disproportionately striking vulnerable children in an area with a weak health-care system.
Can mpox be cured?
Most mpox infections go away on their own without the need for specific treatment, with symptoms typically lasting two to four weeks, according to the Cleveland Clinic. Health experts recommend treating a patient’s symptoms to relieve pain and prevent any complications.
Some treatments developed to treat smallpox — a closely related virus — are thought to be effective at treating mpox infections. One such treatment, the antiviral tecovirimat, widely known as TPOXX, is available in some cases as a treatment to hasten recovery. Its efficacy is still being studied, with a clinical trial underway. The CDC discourages widespread distribution of TPOXX, instead calling for the prioritization of people considered at high risk, including those who are severely immunocompromised, pregnant or children.
Is there an mpox vaccine?
Public health authorities recommend that people who are at high risk — which, depending on the country, can include health workers, sex workers and men who have sex with men — get vaccinated to prevent mpox infection. In the United States, gay and bisexual men and transgender people are considered at risk if within the last six months they have had multiple sexual partners, a sexually transmitted infection, or sex in commercial venues.
Two doses of the vaccine, known as JYNNEOS and developed to prevent smallpox, “work to prevent mpox in most people” and may help protect people from “severe infection, hospitalization, and death,” according to the CDC. But it does not provide full protection, and experts are studying why some vaccinated people have gotten mpox and how long immunity against infection lasts. Officials say the vaccine still appears to provide protection against severe disease, similar to coronavirus vaccines.
Another vaccine, LC16m8, has been approved in Japan and limited research shows it generates antibody response to mpox without serious safety concerns.
The smallpox vaccine ACAM2000 has been used in the past for mpox, but officials generally avoid it, now that there are other options, because of side effects.
The vaccines are not widely available in African countries where the virus is endemic. For people at higher risk in Congo, officials are hoping to distribute vaccines later this year, pending regulatory approval.
What causes mpox?
The virus spreads through exposure to infected animals, contact with bodily fluids and skin-to-skin contact, but not casual or brief touch. Contact during sex emerged as the most effective way for the virus to spread swiftly during the 2022 outbreak, and officials are concerned that the version of the virus now appearing for the first time in some countries is being transmitted the same way, including among heterosexuals, with the potential to seed larger outbreaks.
While sexual transmission raises concerns about the virus crossing borders, mpox also appears to be spreading inside Congolese households and among children through other forms of contact, such as through shared bedding and clothing or parents holding children.
The virus could also transmit through respiratory droplets when people have close face-to-face contact. Public health officials stress that this form of transmission is uncommon and much more difficult than the airborne transmission of pathogens such as the coronavirus that can hang in the air and spread through currents.
Some people can spread mpox before they develop symptoms, and the risk continues until their rash heals and a fresh layer of skin has formed, according to the CDC.
What are the symptoms of mpox?
Once someone is infected, symptoms tend to appear six to 13 days later, although they can sometimes take up to 21 days to appear, according to the ECDC. Symptoms are similar to those of a flu and include fever, headache, back pain and muscle aches — but mpox infections can also cause a distinctive rash on various parts of the body.
“Within three days of experiencing the initial symptoms, the rash may spread quickly and eventually turns into small fluid-filled sacs known as vesicles. If the rash spreads throughout the body, it can also affect the palms of the hands and the soles of the feet,” the ECDC says.
In cases of sexual contact, lesions have appeared around the genitals and anus and have caused intense pain in going to the bathroom.
Is mpox a sexually transmitted infection?
While the sexual spread of mpox has prompted emergency declarations, public health officials have been hesitant to call it a sexually transmitted infection such as syphilis or HIV. This is because the virus spreads in other ways (including in Congolese children), but some critics say this approach is splitting hairs and detracts from effectively responding.
During the 2022 outbreak, Leandro Mena, director of the STD Prevention Division of the National Center for HIV, Viral Hepatitis, STD, and TB Prevention, and Jonathan Mermin, director of the center, said that “although transmission can, and has, occurred through nonsexual contact, many of the health communications, facilities, and programs” used in cases of sexually transmitted infections, including HIV, “are applicable for monkeypox prevention and treatment.”
There was some disagreement among experts in previous outbreaks about whether mpox should be labeled as an STD. In April 2023, six experts from institutions including the University of Southern California and Brigham and Women’s Hospital wrote in a position statement published in the journal Clinical Infectious Diseases that “labeling it as such will help focus public health interventions, such as vaccinations, testing, and treatment, as well as facilitate focused awareness and education programs toward behavioral modifications to reduce exposures.”
How do you avoid getting mpox?
Public health officials advise avoid coming into close contact with infected wild animals, people with mpox, and contaminated materials such as sheets that a person with mpox has slept in. Avoid touching those materials and wash your hands often.
During the height of the 2022 outbreak, the CDC advised sexually active Americans to limit their number of sexual partners until they could be vaccinated.
The CDC also recommends that people who are at risk for mpox get vaccinated, “avoid close, skin-to-skin contact with people who have a rash that looks like mpox and animals that carry the monkeypox virus,” and take steps “to lower your risk of mpox during sex or at a social gathering.”
In Congo, experts say crowded living conditions in displacement camps and the lack of personal protective equipment and disinfectants in health-care facilities have made it difficult to reduce the risk of exposure to mpox.