Introduction

Monkeypox and smallpox are both viral diseases caused by orthopoxviruses, sharing similarities in symptoms and modes of transmission. However, there are significant differences between the two in terms of severity, epidemiology, and public health impact. While smallpox has been eradicated, monkeypox continues to emerge as a public health concern, particularly in regions of Africa. This article provides a comparative analysis of monkeypox and smallpox, highlighting their similarities, differences, and implications for global health.

Similarities Between Monkeypox and Smallpox

Monkeypox and smallpox share several similarities due to their belonging to the same genus, Orthopoxvirus. Both diseases present with a similar clinical course, starting with non-specific symptoms such as fever, headache, and muscle aches, followed by a characteristic rash. The rash in both diseases progresses through similar stages—macules, papules, vesicles, pustules, and scabs. Additionally, the lesions typically appear in a centrifugal distribution, meaning they are most concentrated on the face and extremities.

In terms of transmission, both monkeypox and smallpox can spread through direct contact with infectious lesions, bodily fluids, or contaminated materials like bedding. Respiratory droplets also play a role in transmission, particularly in close-contact settings. Due to these similarities, monkeypox and smallpox are often compared, and the initial suspicion of monkeypox in a patient might arise due to its resemblance to smallpox.

Key Differences Between Monkeypox and Smallpox

1. Causative Agents

• Smallpox is caused by the variola virus, which is highly contagious and deadly.
• Monkeypox is caused by the monkeypox virus, which is less contagious and generally less severe.

2. Epidemiology and Reservoirs

• Smallpox was a human-only disease, with no known animal reservoirs. This characteristic was crucial in the successful global eradication of smallpox in 1980 through vaccination efforts.
• Monkeypox, on the other hand, is a zoonotic disease, meaning it can be transmitted from animals to humans. The primary animal reservoirs are thought to be rodents and other small mammals in African rainforests. This zoonotic nature makes the control and potential eradication of monkeypox more complex.

3. Severity and Mortality

• Smallpox had a high mortality rate, with the variola major strain killing about 30% of those infected. Survivors often had permanent scarring, and some were left blind.
• Monkeypox has a much lower mortality rate, ranging from 1% to 10%, depending on the clade (West African or Central African). However, the West African clade is generally less severe, with lower fatality rates.

4. Lymphadenopathy

• Lymphadenopathy (swollen lymph nodes) is a hallmark of monkeypox and helps differentiate it from smallpox. It typically occurs before the rash appears and is most noticeable in the neck, armpits, and groin.
• Smallpox does not usually cause lymphadenopathy, which is one of the distinguishing clinical features between the two diseases.

5. Global Impact and Current Status

• Smallpox was a significant global health threat until its eradication in 1980, following an aggressive worldwide vaccination campaign. The eradication of smallpox is considered one of the greatest achievements in public health.
• Monkeypox remains endemic in certain parts of Africa, particularly in the Democratic Republic of Congo and Nigeria. In recent years, there have been outbreaks outside of Africa, raising concerns about its potential to spread globally, particularly in regions with low immunity and high levels of interaction with wildlife.

Public Health Implications

1. Surveillance and Response

While smallpox has been eradicated, the emergence of monkeypox in non-endemic areas underscores the need for vigilant surveillance and rapid response capabilities. Public health systems must be prepared to identify and contain outbreaks of monkeypox, especially in areas where the disease is not well-known or where healthcare infrastructure is limited.

2. Vaccination Strategies

The smallpox vaccine, which provided cross-protection against monkeypox, was discontinued after the eradication of smallpox. However, the recent resurgence of monkeypox has led to renewed interest in vaccination. The JYNNEOS (Imvamune or Imvanex) vaccine, which is approved for both smallpox and monkeypox, is being used in outbreak responses. The strategic use of vaccines, especially among high-risk populations and healthcare workers, is crucial in controlling the spread of monkeypox.

3. Public Awareness and Education

Public education campaigns are vital in regions at risk of monkeypox outbreaks. Raising awareness about the modes of transmission, symptoms, and preventive measures can help reduce the spread of the virus. In areas where monkeypox is endemic, communities should be informed about the risks associated with wildlife and the importance of seeking medical attention if symptoms arise.

4. Research and Development

Continued research is needed to better understand monkeypox and its transmission dynamics, particularly in non-endemic regions. Developing effective antiviral treatments and improving vaccines are critical areas of focus. Additionally, studying the potential impact of climate change and deforestation on the emergence of zoonotic diseases like monkeypox is essential for long-term public health planning.

Conclusion

Monkeypox and smallpox, though related, have distinct differences that have significant implications for public health. The eradication of smallpox was a monumental achievement, but monkeypox continues to pose challenges due to its zoonotic nature and potential for outbreaks in non-endemic regions. Public health strategies must adapt to these challenges by enhancing surveillance, promoting vaccination, and increasing public awareness. By learning from the successes of smallpox eradication and applying those lessons to monkeypox, the global community can better prepare for and respond to this emerging threat.