Mpox is spreading rapidly. Here are the questions researchers are racing to answer (2024)

Mpox is spreading rapidly. Here are the questions researchers are racing to answer (1)

When the World Health Organization (WHO) declared a public-health emergency over mpox earlier this month, it was because a concerning form of the virus that causes the disease had spread to multiple African countries where it had never been seen before. Since then, two people travelling to Africa — one from Sweden and one from Thailand — have become infected with that type of virus, called clade 1b, and brought it back to their countries.

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Although researchers have known about the current outbreak since late last year, the need for answers about it is now more pressing than ever. The Democratic Republic of the Congo (DRC) has spent decades grappling with monkeypox clade I virus — a lineage to which Ib belongs. But in the past, clade I infections usually arose when a person came into contact with wild animals, and outbreaks would fizzle.

Clade Ib seems different, and is spreading largely through contact between humans, including through sex. Around 18,000 suspected cases of mpox, many of them among children, and at least 600 deaths potentially attributable to the disease have been reported this year in the DRC alone.

How does this emergency compare with one declared in 2022, when mpox cases spread around the globe? How is this virus behaving compared with the version that triggered that outbreak, a type called clade II? And will Africa be able to rein this one in? Nature talks with researchers about information they are rushing to gather.

Is clade Ib more deadly than the other virus types?

It’s hard to determine, says Jason Kindrachuk, a virologist at the University of Manitoba in Winnipeg, Canada. He says that the DRC is experiencing two outbreaks simultaneously. The clade I virus, which has been endemic in forested regions of the DRC for decades, circulates in rural regions where people get it from animals. That clade was renamed Ia after the discovery of clade Ib. Studies in animals suggest that clade I is deadlier than clade II1 — but Kindrachuk says that it’s hard to speculate on what that means for humans at this point.

Even when not fatal, mpox can trigger fevers, aches and painful fluid-filled skin lesions.

Growing mpox outbreak prompts WHO to declare global health emergency

Although many reports state that 10% of clade I infections in humans are fatal, infectious-disease researcher Laurens Liesenborghs at the Institute of Tropical Medicine in Antwerp, Belgium, doubts that this figure is accurate. Even the WHO’s latest estimate of a 3.5% fatality rate for people with mpox in the DRC might be high.

There are many reasons that fatality estimates might be unreliable, Liesenborghs says. For one, surveillance data captures only the most severe cases; many people who are less ill might not seek care at hospitals or through physicians, so their infections go unreported.

Another factor that can confound fatality rates is a secondary health condition. For example, people living with HIV — who can represent a large proportion of the population in many African countries — die from mpox at twice the rate of the general population2, especially if their HIV is untreated. And the relatively high death rate among children under age 5 could be partly because of malnutrition, which is common among kids in rural parts of the DRC, Liesenborghs says.

Is clade Ib more transmissible than other types?

The clade 1b virus has garnered particular attention because epidemiological data suggest that it transmits more readily between people than previous strains did, including through sexual activity, whereas clade Ia mostly comes from animals. An analysis posted ahead of peer review on the preprint server medRxiv3 shows that clade Ib’s genome contains genetic mutations that seem to have been induced by the human immune system, suggesting that it has been in humans for some time. Clade Ia genomes have fewer of these mutations.

But Liesenborghs says that the mutations and clades might not be the most important factor in understanding how monkeypox virus spreads. Although distinguishing Ia from Ib is useful in tracking the disease, he says, the severity and transmissibility of the disease could be affected more by the region where the virus is circulating and the people there. Clade Ia, for instance, seems to be more common in sparsely populated rural regions where it is less likely to spread far. Clade Ib is cropping up in densely populated areas and spreading more readily.

Jean Nachega, an infectious-disease physician at the University of Pittsburgh in Pennsylvania, says that scientists don’t understand many aspects of mpox transmission — they haven’t even determined which animal serves as a reservoir for the virus in the wild, although rodents are able to carry it. “We have to be very humble,” Nachega says.

How effective are vaccines against the clade I virus?

Just as was the case during the COVID-19 pandemic, health experts are looking to vaccines to help curb this mpox outbreak. Although there are no vaccines designed specifically against the monkeypox virus, there are two vaccines proven to ward off a related poxvirus — the one that causes smallpox. Jynneos, made by biotechnology company Bavarian Nordic in Hellerup, Denmark, contains a type of poxvirus that can’t replicate but can trigger an immune response. LC16m8, made by pharmaceutical company KM Biologics in Kumamoto, Japan, contains a live — but weakened — version of a different poxvirus strain.

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Still, it’s unclear how effective these smallpox vaccines are against mpox generally. Dimie Ogoina, an infectious-disease specialist at Niger Delta University in Wilberforce Island, Nigeria, points out that vaccines have been tested only against clade II virus in European and US populations, because these shots were distributed by wealthy nations during the 2022 global outbreak. And those recipients were primarily young, healthy men who have sex with men, a population that was particularly susceptible during that outbreak. One study in the United States found that one dose of Jynneos was 80% effective at preventing the disease in at-risk people, whereas two doses were 82% effective4; the WHO recommends getting both jabs.

People in Africa infected with either the clade Ia or 1b virus — especially children and those with compromised immune systems — might respond differently. However, one study in the DRC found that the Jynneos vaccine generally raised antibodies against mpox in about 1,000 health-care workers who received it5.

But researchers are trying to fill in some data gaps. A team in the DRC is about to launch a clinical trial of Jynneos in people who have come into close contact with the monkeypox virus — but have not shown symptoms — to see whether it can prevent future infection, or improve outcomes if an infection arises.

Will the vaccines help to rein in the latest outbreak?

Mpox vaccines have been largely unavailable in Africa, but several wealthy countries have pledged to donate doses to the DRC and other affected African nations. The United States has offered 50,000 Jynneos doses from its national stockpile, and the European Union has ordered 175,000, with individual member countries pledging extra doses. Bavarian Nordic has also added another 40,000. Japan has offered 3.5 million doses of LC16m8 — for which only one jab is recommended instead of two.

Monkeypox in Africa: the science the world ignored

None of them have arrived yet, though, says Espoir Bwenge Malembaka, an epidemiologist at the Catholic University of Bukavu in the DRC. Low- and middle-income nations cannot receive vaccines until the WHO has deemed the jabs safe and effective. And the WHO has not given its thumbs up yet. It is evaluating data from vaccine manufacturers, delaying donors’ ability to send the vaccines.

Even when the vaccines arrive, Bwenge Malembaka says, “it’s really a drop in the bucket”. The African Centres for Disease Control and Prevention in Addis Ababa, Ethiopia, estimates that 10 million doses are needed to rein in the outbreak.

Bwenge Malembaka says that the uncertainty over vaccine arrival has made it difficult for the government to form a distribution plan. “I don’t know how one can go about this kind of challenge,” he says. Bwenge Malembaka suspects that children are likely to receive doses first, because they are highly vulnerable to clade I, but officials haven’t decided which regions to target. It’s also unclear how the government would prioritize other vulnerable populations such as sex workers, who have been affected by clade Ib. Their profession is criminalized in the DRC, so they might not be able to come forward for treatment.

Researchers lament that public-health organizations didn’t provide vaccines and other resources as soon as the clade I outbreak was identified, especially given lessons learnt from the 2022 global mpox outbreak. “The opportunity was there a couple months ago to cut this transmission chain, but resources weren’t available,” Liesenborghs says. “Now, it will be more challenging to tackle this outbreak, and the population at risk is much broader.”

Mpox is spreading rapidly. Here are the questions researchers are racing to answer (2024)

FAQs

What is mpox and how is it spread? ›

The mpox virus causes mpox. The virus spreads through close contact with an infected animal or person. Or it can spread when a person handles materials such as blankets that have been in contact with someone who has mpox.

Where is mpox spreading? ›

There are outbreaks of clade I mpox in the Democratic Republic of the Congo (DRC) that began in 2023. The outbreak on the eastern part of the country has spread into neighboring countries in 2024. Mpox is spread by mainly through skin-to-skin contact.

Is there a cure for mpox? ›

Overview. Currently there is no treatment approved specifically for monkeypox virus (MPXV) infections. For most patients with mpox who have intact immune systems and don't have a skin disease, supportive care and pain control will help them recover without medical treatment.

What is the mortality rate of mpox? ›

There are two strains of mpox, clade 1 and clade 2. Clade 1 is the more severe strain, with a fatality rate of 3.6%, that is currently spreading in Central and East Africa. Clade 2, with less severe illness and less than 0.2% fatality rate, was the strain responsible for the 2022 outbreak originating in West Africa.

What does mpox rash look like? ›

These bumps can look like a blister, pus-filled bump, or open sore. Even with a few bumps, the rash can be painful.

What are the symptoms of mpox in adults? ›

Common symptoms of mpox are a skin rash or mucosal lesions which can last 2–4 weeks accompanied by fever, headache, muscle aches, back pain, low energy and swollen lymph nodes. Mpox can be transmitted through close contact with someone who has mpox, with contaminated materials, or with infected animals.

What are the symptoms of mpox 2024? ›

People with mpox often get a rash and may have other symptoms like fever, chills, and swollen lymph nodes. Symptoms usually start within 21 days of exposure. Visit a healthcare provider if you have a new or unexplained rash, especially after contact with someone who has mpox.

How to avoid monkeypox? ›

Other ways to prevent mpox
  1. Avoiding contact with infected animals (especially sick or dead animals).
  2. Avoiding contact with bedding and other materials contaminated with the virus.
  3. Thoroughly cooking all foods that contain animal meat or parts.
  4. Washing your hands frequently with soap and water.

How many cases of mpox are there in the US? ›

Since 2022, the U.S. has had outbreaks of clade II mpox, mostly among men who have sex with men, but also in some nonbinary and transgender people, according to recent CDC data. Overall, more than 32,000 people in the U.S. have been infected and 58 have died of mpox.

Is mpox serious? ›

In most cases, the symptoms of mpox go away on their own within a few weeks with supportive care, such as medication for pain or fever. However, in some people, the illness can be severe or lead to complications and even death.

Does monkeypox go away on its own? ›

Most people recover without treatment after a few weeks. In rare cases, people can become very sick and die. People usually develop symptoms 7 to 10 days after being exposed to the monkeypox virus. However, the time it takes to develop symptoms can range from 3 to 21 days after being exposed.

Is monkeypox an STD? ›

STDs are those conditions in which intimate sexual contact is important to transmission, and sexual contact is the transmission center. However, monkeypox is one of those conditions when only intimate touch, not sexual activity, is involved.

How contagious is mpox? ›

Mpox can be passed on from person to person through: any close physical contact with mpox blisters or scabs (including during sexual contact, kissing, cuddling or holding hands) touching clothing, bedding or towels used by someone with mpox. the coughs or sneezes of a person with mpox when they're close to you.

Is there a mpox vaccine? ›

There are two FDA-approved vaccines for the prevention of smallpox and mpox disease: JYNNEOS and ACAM2000. These two vaccines are the only FDA-approved vaccines for the prevention of mpox disease.

What disease has the highest death toll? ›

The world's biggest killer is ischaemic heart disease, responsible for 13% of the world's total deaths. Since 2000, the largest increase in deaths has been for this disease, rising by 2.7 million to 9.1 million deaths in 2021.

Is mpox an STD? ›

While the monkeypox virus has been found in semen, it is currently not known whether mpox can be spread through semen or vaginal fluids. Wearing a condom won't fully protect you from mpox, but it may reduce your risk or extent of exposure and it will help protect you and others from HIV and a range of other STIs.

How to get rid of monkeypox? ›

Care and Treatment for Monkeypox

There is no specific treatment approved for monkeypox. However, an antiviral called tecovirimat (TPOXX), approved to treat smallpox, can be used for people who are at high risk for severe illness or have severe symptoms from monkeypox.

Where does monkeypox come from? ›

There are two known types (clades) of mpox virus — one that originated in Central Africa (Clade I) and one that originated in West Africa (Clade II). The current world outbreak (2022 to 2023) is caused by Clade IIb, a subtype of the less severe West African clade.

How is molluscum spreading all over the body? ›

If you have molluscum, you can spread it to other areas of your body. This can happen if you touch or scratch the sores, shave over them or have hair removal procedures on the area. You can also catch molluscum if you have sex with someone who has it. Many molluscum infections in adults occur this way.

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