Monkeypox vs. Smallpox: All about symptoms, treatment, and vaccination

Monkeypox and smallpox are both viral diseases caused by viruses from the same genus family, Poxviridae, but they have distinct differences in terms of symptoms, severity, and treatments. Smallpox, one of the most concerning and deadly diseases in human history, was caused by the variola virus. In 1980, it became the first disease to be eradicated through vaccination efforts by the World Health Organization (WHO).
Smallpox is an animal-borne infection that showed symptoms such as high fever, severe fatigue, and painful rashes that turned into pus-filled sores all over the body. Survivors were often left with permanent scars (pockmarks) and, in some cases, blindness.
A distinction of variabilities between these two diseases is critical for diagnosis, treatment, and prevention methods.
What are the symptoms of monkeypox?
Mpox is caused by the monkeypox virus (MPXV), an enveloped double-stranded DNA virus from the Orthopoxvirus genus, which includes variola, cowpox, and vaccinia viruses. While most individuals recover fully, some cases can be severe. The virus exists in two main clades: clade I (with subclades Ia and Ib) and clade II (with subclades IIa and IIb). A global outbreak of clade IIb began in 2022 and continues, with clade Ia and Ib also causing infections, particularly in Africa and, as of August 2024, beyond Africa.
The exact natural reservoir of MPXV remains unknown, but small mammals like squirrels and monkeys are susceptible. Mpox spreads mainly through close contact with infected people, contaminated objects, or needle injuries. It can also be transmitted from animals via bites or scratches. Transmission during pregnancy can be highly risky for the fetus or newborn.
Initially, this disease often manifests with some quite alarming symptoms. Such symptoms include fever, headache, muscle ache, backache, swollen lymph nodes, and the feeling of chills. Then, the symptoms are followed by a characteristic rash. Which begins as flat lesions that become raised bumps while progressing. These bumps grow into pustules before they crust over. The rash typically starts on the face and spreads to the rest of the body parts, such as the soles and palms. This entire process starting from the initial symptoms to the disappearance of the rash usually ranges from 2 to 4 weeks.
What distinguishes smallpox from monkeypox?
Although smallpox is due to a different strain of Orthopoxvirus, the symptoms and course are distinct. It starts with a sudden extremely high fever along with fatigue headache and back pain. The rash caused by smallpox starts as small reddened spots on the face and quickly develops on the rest of the body. Unlike monkeypox, in smallpox, lesions tend to come out roughly and evolve in an orderly sequence from macules to papules, to pustules, and then crusting. The duration is about 2 to 4 weeks for smallpox, as with monkeypox, peaking in the second week with the rash. However, smallpox has been eradicated all over the world due to a successful vaccination program that made this element of its management and symptoms a historical study rather than any concern in the present day.
How are monkeypox and smallpox treated?
The treatment for monkeypox mostly involves supportive care. That includes hydration, management of pain, and treating the secondary bacterial infections that could be developing. The antiviral drug for smallpox called tecovirimat could also be considered for monkeypox in certain situations, although they are not commonly approved for general use. Unlike this, smallpox relied mainly on immunization, through antiviral drugs like cidofovir and tecovirima. Supportive care also played an essential role in managing symptoms and preventing complications in smallpox cases.
Available options for vaccinations
Vaccination efforts against monkeypox are in development. Since the genetic variations between the viruses that cause smallpox and monkeypox are minor, the smallpox vaccine provides some level of cross-protection against the monkeypox virus. Specifically, modified vaccines like Jynneos have been engineered for use specifically to target monkeypox and now are in circulation to increase protection.
In summary, the comparison between monkeypox and smallpox highlights both the strides we've made in public health and the challenges that remain. While smallpox has been eradicated through a successful global vaccination campaign, monkeypox has emerged as a notable concern due to its recent spread beyond endemic regions. The evolving nature of monkeypox outbreaks emphasizes the importance of global vigilance, enhanced surveillance, and targeted vaccination strategies, such as the use of modified smallpox vaccines. This ongoing situation serves as a crucial reminder of the need for continued research and adaptability in our approach to infectious diseases. By learning from past successes and remaining proactive, we can better navigate current health challenges and prepare for future threats.
(Author: Dr. Ravi Kesari, MD - Physician, General Physician, Apollo Spectra Hospital, Bangalore)