Understanding the Mpox Strain: Key Information for 2024 and Beyond

The global health landscape has been significantly shaped by the recent spread of a new mpox strain. Formerly known as monkeypox, mpox is a viral disease that has garnered increased attention due to its evolving patterns and impact on public health. As of 2024, it is crucial to stay informed about the latest developments surrounding this virus, especially with the emergence of a more severe strain.

What is Mpox?

Mpox is a zoonotic disease, meaning it is transmitted from animals to humans. The virus is part of the Orthopoxvirus genus, which includes other viruses like smallpox. Mpox is characterized by its distinctive symptoms, which often include a painful rash that can progress to lesions, as well as fever, headaches, muscle aches, and swollen lymph nodes. While the disease shares similarities with smallpox, it is generally less severe and less contagious.

The Two Clades of Mpox

Mpox is classified into two main genes Clade I and Clade II. These clades represent different genetic lineages of the virus, each with distinct characteristics and implications for public health.

• Clade I: This clade has been associated with more severe symptoms and higher mortality rates compared to Clade II. Historically, Clade I has been confined primarily to Central Africa, particularly in the Democratic Republic of Congo (DRC). It is known for causing outbreaks with a mortality rate of up to 10% in some cases, though recent data suggests a somewhat lower fatality rate in current outbreaks.
• Clade II: Clade II was responsible for the widespread global outbreak in 2022, which garnered significant international attention. This clade is divided into two subgroups, Clade IIa, and Clade IIb, with Clade IIb being the primary cause of the 2022 outbreak. Clade II generally exhibits lower mortality rates, with around 1% in African outbreaks and even lower rates globally. The virus was predominantly spread through close, often intimate contact, which led to a significant number of cases among men who have sex with men (MSM).

The Emergence of a New Mpox Strain in 2023

In early 2023, a concerning development occurred with the emergence of a new variant of Clade I in the DRC. This variant, often referred to as Clade Ib, has shown a troubling ability to spread more efficiently from person to person, compared to earlier versions of the virus. Unlike the 2022 outbreak, which was largely contained through public health measures and vaccination campaigns, this new strain has demonstrated different transmission dynamics and a potentially higher level of virulence, raising concerns about its impact on both physical and mental health as communities grapple with the uncertainty and fear surrounding the outbreak.

The outbreak began in January 2023 and quickly spread beyond the borders of the DRC, affecting several other countries in Central and East Africa. By mid-2023, cases of Clade Ib had been reported in over a dozen countries in the region. In a significant development, Sweden confirmed the first case of Clade Ib outside Africa, marking the potential for a broader international spread. Although the patient was believed to have contracted the virus while in Africa, the case raised alarms about the global mobility of this more severe strain.

How Does the New Mpox Strain Spread?

The transmission of mpox has traditionally occurred through several routes:

• Direct contact with an infected person: This includes skin-to-skin contact with lesions, as well as contact with bodily fluids such as saliva or respiratory droplets.
• Contact with contaminated objects: Mpox can survive on surfaces like clothing, bedding, and other materials that have been in contact with an infected person.
• Animal-to-human transmission: This occurs through direct contact with infected animals, including rodents and primates, or the consumption of undercooked meat from these animals.

In the 2022 outbreak, Clade IIb primarily spread through close personal contact, especially during sexual activity. The current outbreak involving Clade Ib has shown similar transmission patterns but with a broader range of transmission routes being observed. For example, in the DRC, there have been reports of the virus spreading within households and through occupational exposure, such as among healthcare workers and those involved in animal handling.

Additionally, there are indications that sexual contact remains a significant route of transmission for Clade Ib. Unpublished research has linked outbreaks in certain areas to professional sex work, particularly in regions with limited public health infrastructure and surveillance capabilities.

Severity and Symptoms of the New Mpox Strain

The severity of mpox can vary significantly depending on several factors, including the viral strain, the route of transmission, and the individual’s immune status. Historically, Clade I has been associated with more severe disease outcomes, and this trend appears to be continuing with the new Clade Ib variant.

Recent outbreaks of Clade Ib in the DRC have reported a fatality rate of just over 5%, which is lower than previous Clade I outbreaks but still concerning. Out of approximately 22,000 reported cases, more than 1,200 deaths have been attributed to this strain. This suggests that while Clade Ib is less deadly than its predecessors, it remains a serious public health threat, particularly in areas with limited access to healthcare.

The symptoms of Clade Ib infection are generally similar to those of other mpox strains, but with some notable differences:

• Rash and Lesions: The disease often begins with a rash that evolves into pustules and eventually scabs over. In recent outbreaks, there has been an increased incidence of lesions occurring in the genital and perianal regions, which may be linked to sexual transmission.
• Systemic Symptoms: Fever, headache, muscle aches, and swollen lymph nodes are common. Severe cases can lead to complications such as pneumonia, encephalitis (swelling of the brain), and secondary bacterial infections.
• Atypical Presentations: Immunocompromised individuals may experience more severe and atypical symptoms, including larger, more widespread lesions and a higher risk of hospitalization.

It is also worth noting that while vaccines developed for Clade II are expected to offer some protection against Clade I, their effectiveness may vary. In the United States, where mpox vaccines are widely available, it is believed that individuals who have been vaccinated or who have recovered from a previous Clade II infection should have some degree of immunity against severe illness caused by Clade Ib. However, continued surveillance and research are needed to confirm the level of cross-protection provided by these vaccines.

Implications for Public Health and Preparedness

The emergence of the Clade Ib strain of mpox underscores the importance of ongoing vigilance and preparedness in global public health. The World Health Organization (WHO) and other health agencies have been closely monitoring the situation, issuing guidelines to help countries detect, respond to, and contain outbreaks.

For countries outside Africa, the risk posed by Clade Ib may be lower, but it is not negligible. The case in Sweden serves as a reminder that international travel and trade can facilitate the spread of infectious diseases across borders. Public health authorities in the United States and other regions are urged to maintain strong surveillance systems, ensure the availability of vaccines and treatments, and provide clear communication to the public about the risks and preventive measures associated with mpox.

Conclusion: Staying Informed and Protected

As we move further into 2024, it is clear that mpox remains a dynamic and evolving threat to global health. The new Clade Ib strain has introduced additional challenges, particularly in terms of its transmissibility and severity. However, by staying informed and following public health guidelines, individuals and communities can take steps to protect themselves and reduce the spread of the virus.

Key takeaways for those concerned about mpox include the importance of vaccination, particularly for those in high-risk groups, and the need for continued public health vigilance. Understanding the differences between the various strains of the virus and how they spread can help people make informed decisions about their health and safety.

By focusing on evidence-based information and adhering to best practices in public health, we can collectively manage the risks associated with mpox and work towards minimizing its impact in the years to come.