Monkeypox in Endemic vs Non-Endemic Regions Epidemiology

Introduction

Monkeypox is a zoonotic viral disease caused by the monkeypox virus, belonging to the Orthopoxvirus genus, which also includes the variola virus responsible for smallpox. Although monkeypox is generally less severe than smallpox, it remains a significant public health concern, particularly in regions where it is endemic. Recently, monkeypox has garnered global attention due to outbreaks in non-endemic regions, highlighting the importance of understanding the disease’s epidemiology across different settings. This article explores the epidemiology of monkeypox in endemic versus non-endemic regions, examining factors that influence the spread, impact, and control measures in each context.

Monkeypox in Endemic Regions

1. Geographic Distribution

Monkeypox is endemic to parts of Central and West Africa, with the Democratic Republic of the Congo (DRC), Nigeria, and other neighboring countries reporting the highest number of cases. The virus circulates primarily in tropical rainforest areas where humans and wildlife, particularly rodents and primates, come into close contact. The disease was first identified in humans in the DRC in 1970, and since then, sporadic outbreaks have occurred, predominantly in rural areas.

2. Epidemiological Characteristics

In endemic regions, monkeypox is often associated with direct contact with wildlife, particularly through hunting, handling, or consuming bushmeat. Rodents, such as squirrels and Gambian pouched rats, are believed to be the primary reservoirs of the virus. Human-to-human transmission is less common but can occur through respiratory droplets, contact with body fluids, or contaminated objects.

The disease predominantly affects children and young adults in these regions, with males often being more frequently infected due to their involvement in hunting and other outdoor activities. In endemic areas, the disease has a seasonal pattern, with cases typically peaking during the dry season when hunting and agricultural activities increase.

3. Clinical Features and Mortality

In endemic regions, monkeypox presents with a range of symptoms, including fever, headache, muscle aches, and a characteristic rash that progresses from macules to pustules and scabs. Lymphadenopathy, or swollen lymph nodes, is a distinguishing feature of monkeypox compared to other poxvirus infections.

The case fatality rate (CFR) in endemic areas varies depending on the clade of the virus. The Central African (Congo Basin) clade is associated with a higher CFR, ranging from 1% to 10%, while the West African clade typically has a lower CFR, around 1% to 3%. However, the impact of monkeypox on mortality and morbidity in endemic regions is exacerbated by limited access to healthcare, poor infrastructure, and the presence of other endemic diseases, such as malaria and HIV/AIDS.

4. Challenges in Disease Control

Controlling monkeypox in endemic regions is challenging due to several factors:

• Limited Surveillance and Reporting: In many endemic areas, health infrastructure is weak, leading to underreporting and delays in identifying outbreaks. Many cases go undetected, and there is a lack of comprehensive surveillance systems to monitor the disease.
• Cultural Practices: The hunting and consumption of bushmeat, a significant source of protein for many communities, pose a persistent risk for zoonotic transmission. Efforts to change these practices are often met with resistance due to cultural and economic factors.
• Vaccination Gaps: The discontinuation of routine smallpox vaccination after the eradication of smallpox has left younger populations susceptible to monkeypox, as the smallpox vaccine provides cross-protection against monkeypox.

Monkeypox in Non-Endemic Regions

1. Emergence and Spread

In recent years, monkeypox has emerged as a concern in non-endemic regions, particularly in Europe, North America, and Asia. These outbreaks are usually linked to international travel, trade of exotic pets, or contact with infected individuals from endemic regions. The first major outbreak in a non-endemic country occurred in the United States in 2003, linked to the importation of infected Gambian pouched rats from Africa.

The 2022 global outbreak of monkeypox, which spread to multiple countries outside Africa, was unprecedented in scale. The outbreak was driven by human-to-human transmission, particularly in social networks involving close physical contact. Unlike in endemic regions, the spread in non-endemic areas was facilitated by different factors, including international travel, high population density, and delayed detection and response.

2. Epidemiological Characteristics

In non-endemic regions, monkeypox outbreaks tend to involve different demographic groups compared to endemic regions. The 2022 outbreak, for example, predominantly affected men who have sex with men (MSM), a pattern that differed significantly from the more general population affected in endemic areas. This difference highlights the importance of understanding transmission dynamics in different contexts.

The disease’s spread in non-endemic areas has also been characterized by higher levels of person-to-person transmission, including through sexual contact, which was less emphasized in previous outbreaks. This has led to the consideration of monkeypox as a sexually transmitted infections (STI) in certain contexts, although it is not traditionally classified as such.

3. Clinical Features and Outcomes

In non-endemic regions, monkeypox generally presents with similar symptoms to those seen in endemic areas, including fever, rash, and lymphadenopathy. However, the disease has been less severe, with lower mortality rates reported outside of Africa. This may be due to better access to healthcare, early detection, and supportive care in more developed health systems.

4. Response and Control Measures

The response to monkeypox outbreaks in non-endemic regions has highlighted the importance of rapid public health interventions:

• Surveillance and Contact Tracing: Non-endemic countries have implemented robust surveillance and contact tracing efforts to identify and isolate cases quickly. These measures are critical in preventing the further spread of the virus.
• Vaccination Campaigns: In response to the 2022 outbreak, countries such as the United States and the United Kingdom deployed vaccines, including the JYNNEOS vaccine, which is effective against both smallpox and monkeypox. Targeted vaccination campaigns focused on high-risk populations, including healthcare workers and MSM.
• Public Health Messaging: Effective communication strategies have been employed to raise awareness about the symptoms of monkeypox, modes of transmission, and prevention measures. Public health messaging has been particularly important in reaching vulnerable populations and reducing stigma associated with the disease.

Global Implications and Conclusion

The global epidemiology of monkeypox reveals significant differences between endemic and non-endemic regions in terms of transmission dynamics, affected populations, and response strategies. In endemic regions, the challenge lies in addressing the root causes of zoonotic transmission, improving surveillance, and strengthening healthcare infrastructure. In non-endemic regions, rapid detection, contact tracing, and vaccination are crucial to containing outbreaks.

The recent global spread of monkeypox underscores the interconnectedness of our world and the need for a coordinated international response to emerging infectious diseases. As the world continues to face the threat of zoonotic diseases, the lessons learned from monkeypox can inform broader efforts to prevent and control future outbreaks, ensuring that both endemic and non-endemic regions are better prepared to respond to public health emergencies.