Mpox: understand the outbreak with a more lethal variant

The World Health Organization (WHO) declared, this Wednesday (14), that the current outbreak of mpox in Africa is a global health emergency . The statement comes after the entity convened the emergency committee amid concerns that a more lethal strain of the virus could spread to non-endemic regions of the disease.

Fifteen African countries are reporting outbreaks of mpox with a total of 2,030 confirmed cases and 13 deaths this year, according to the WHO. The current concern is that the version of the virus spreading in Africa is not the same as the one in the 2022 global outbreak, which was milder. The current strain circulating in the region is more lethal and potentially more transmissible.

“Historically, there was a group of viruses that circulated in West Africa, which is called clade 2, and another large group of viruses that circulated in the Democratic Republic of Congo and adjacent countries, which was called clade 1,” explains Giliane Trindade, professor of Microbiology at the Institute of Biological Sciences at the Federal University of Minas Gerais (ICB – UFMG), CNN .

“This clade 1 is the one that is in open transmission in the Democratic Republic of Congo and it has greater virulence than clade 2, so it causes a more serious clinical picture”, he adds.

In September 2023, a subvariant of clade 1 – dubbed clade 1B – emerged in the Democratic Republic of the Congo and is also considered more lethal than clade 2. Cases of mpox caused by the new strain have also been reported in Rwanda, Uganda and Kenya. Analysis is currently underway in Burundi to determine whether recent cases are linked to the new variant.

What is mpox?

Mpox is a disease caused by the mpox virus, of the genus Orthopoxvirus and family Poxviridae. The virus is transmitted to humans through contact with infected people or materials contaminated with the virus. The disease can spread through close contact, such as touching, kissing or sex, as well as through contaminated materials such as sheets, clothing and needles, according to the WHO.

The main symptoms of the disease are skin lesions, which may be accompanied by fever, body aches, headache, chills and weakness. According to the Ministry of Health, the time interval between the first contact with the virus and the onset of signs and symptoms of mpox varies from 3 to 16 days, but can reach 21 days.

Skin lesions may be flat or slightly raised and are filled with a clear or yellowish liquid. As the disease progresses, crusts may form, which dry and fall off. Lesions may be concentrated on the face, palms of the hands and soles of the feet, but they can also appear on other parts of the body, including the mouth, eyes, genitals and anus.

What is a clade?

The mpox virus is divided into two genetic clades: 1 and 2. Clades are groups of viruses that, despite having genetic similarities, are not identical. “These two large groups contain viral isolates that have differences, for example, in relation to the genes that interact with the host’s immune system, which is what we call immunomodulation,” explains Trindade.

According to the Centers for Disease Control and Prevention (CDC), clade 1 causes more severe disease and is more lethal than clade 2. Clade 1 is endemic in the Democratic Republic of the Congo and is responsible for the current outbreak. Clade 2 was responsible for the global outbreak that began in 2022, according to the CDC. In Brazil, the current cases are linked to the circulation of clade 2.

In September 2023, a new variant of the disease was identified, named clade 1B. According to the WHO, the spread of the new variant in the Democratic Republic of the Congo is linked to transmission through sexual contact and high population movement.

“The WHO’s biggest fear is that clade 1 will leave the Democratic Republic of Congo and spread throughout the world, which is what happened with clade 2 in 2022,” explains infectious disease specialist Álvaro Costa, CNN . Mpox is the central theme of his doctoral research.

“At that time, all the cases of mpox were concentrated in Africa, and the cases in other regions were imported from people traveling there, and suddenly we had an outbreak. The pressure now is to prevent a global outbreak with this other variant,” adds the expert.

Why is the new variant more lethal?

According to the CDC, the current outbreak of mpox in the Democratic Republic of the Congo is more widespread than any previous outbreak in the region and has a higher fatality rate. This year alone, the Democratic Republic of the Congo has recorded 14,000 cases of mpox and 511 deaths. This is already higher than the 2022 outbreak, caused by clade 2: despite 85,000 cases recorded, there were only 120 deaths.

“Clade 1 has been known since the 1970s, but what we have now is the emergence of a new lineage within this clade, which is 1B. This lineage harbors some mutations that reflect high transmissibility in humans,” explains Trindade. “The symptoms are very similar, but the lethality is higher,” he adds.

Costa adds that the small genetic variations present in each clade are what can define the severity of the disease’s symptoms, but more studies that analyze the virus’ genetic sequence need to be carried out to understand these differences. “What we already know is that it is more lethal and is causing more deaths. But why the clinical picture is more severe still needs to be studied further,” he says.

Could a new variant reach Brazil?

In Trindade’s view, there is a chance that the new variant will spread to other regions of the world besides Africa. “We live in a globalized world, and what we are seeing in the Democratic Republic of Congo is that it is a highly transmissible variant. So, there is community transmission happening and this is not under control. So, it is always a risk when associated with the globalization factor,” says the professor.

Given this scenario, the Ministry of Health called a meeting last Tuesday (13) to discuss the disease. In a note, the ministry informed that the proposal is to update the recommendations and the contingency plan for the disease in the country.

Also according to the statement, the ministry “closely monitors” the situation of mpox in the world and monitors information with the World Health Organization (WHO) and institutions such as the United States Centers for Disease Control and Prevention (CDC).

How is mpox treated?

There is still no specific medication to treat MPOX. Therefore, treatment aims to alleviate symptoms, prevent and treat complications and sequelae and is therefore based on clinical support measures. Most treated patients recover within a month, but the disease can be fatal if left untreated.

Does vaccination work to prevent the new strain?

One of the main ways to prevent MPOX is through vaccination. In Trindade’s view, a vaccine that already protects against clade 2 can protect against clade 1. “From a genetic point of view, these viruses are very conserved, which is good in the case of vaccines,” he says.

According to the Ministry of Health, the vaccination strategy prioritizes the protection of people at greatest risk of developing more severe forms of the disease. Pre-exposure vaccination is recommended for people living with HIV and laboratory professionals who work directly with the virus in laboratories with biosafety level 2 (NB-2), aged 18 to 49.

The post-exposure vaccine is aimed at people who have had direct contact with bodily fluids and secretions from people suspected, probable or confirmed to have mpox, whose exposure is classified as high or medium risk, according to WHO recommendations.

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