Difference Between Smallpox And Chickenpox

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3.5 Minute

13-09-2024 Team Medicover general-medicine

Written by Medicover Team and Medically Reviewed by Dr Mopidevi Raghuvarma, General Medicine

Smallpox vs Chickenpox: Key Differences

Infectious diseases such as smallpox and chickenpox have significantly impacted human history. Despite their similar names and some overlapping symptoms these two diseases are caused by different viruses and have distinct characteristics.

Understanding the differences between smallpox and chickenpox is crucial for accurate diagnosis, effective treatment and appropriate public health responses.

What is Smallpox?

Smallpox is an acute, contagious disease caused by the variola virus. It has a high mortality rate and has historically caused widespread epidemics. The World Health Organization (WHO) declared smallpox eradicated in 1980 after a successful global vaccination campaign. However, the potential use of smallpox as a bioterrorism agent necessitates continued awareness and preparedness.

Characteristics of Smallpox

A high fever, malaise and a distinctive progressive skin rash characterize smallpox. The rash typically starts on the face and extremities before spreading to the trunk. The lesions evolve from macules to papules, vesicles, pustules and finally, scabs. One of the hallmark signs of smallpox is that all the lesions are at the same stage of development at any given time.

Smallpox Contagiousness

Smallpox is a highly contagious disease that spreads mainly through respiratory droplets when an infected person coughs or sneezes. It can also be transmitted by touching contaminated items like clothing or bedding. A person becomes contagious when the fever starts and remains so until the final scab has fallen off.

Smallpox Scars

Scarring is a common outcome for smallpox survivors. The pustules leave deep, pitted scars, often most prominently on the face, which can be disfiguring.

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What is Chickenpox?

Chickenpox on the other hand, is caused by the varicella-zoster virus, which is a member of the herpesvirus family. It is generally a less severe disease compared to smallpox and is most commonly seen in children, although adults can also contract it. Chickenpox is usually mild but it can lead to severe complications in specific populations, such as newborns, pregnant women and immunocompromised individuals.

Characteristics of Chickenpox

Chickenpox presents with a mild fever, malaise and an itchy rash that typically starts on the chest, back and face before spreading to other parts of the body. The rash progresses from red spots to fluid-filled blisters (vesicles) and finally scabs. Unlike smallpox, chickenpox lesions appear in waves, so new spots appear as older ones crust over.

Chickenpox Contagiousness

Chickenpox is highly contagious and can spread through direct contact with the rash or through respiratory droplets. The infectious period begins 1-2 days before the rash appears and lasts until all the lesions have crusted over.

Chickenpox Rash Characteristics

The rash of chickenpox is typically itchy and uncomfortable but generally does not leave scars unless the blisters are scratched and become infected. If scars occur, they are usually superficial and less disfiguring than those caused by smallpox.

Critical Differences Between Smallpox and Chickenpox

Although both diseases involve fever and a skin rash, they are fundamentally different in origin, severity, progression and public health impact. Understanding these differences is essential for accurate diagnosis, prevention and response strategies.

1. Virus Comparison

The variola virus causes smallpox, while the varicella-zoster virus causes chickenpox. Although both viruses are members of the poxvirus family they belong to different genera and have distinct biological behaviors.

2. Symptom Differences

The symptoms of smallpox and chickenpox can be initially similar, with both diseases presenting with fever and malaise. However, smallpox is generally more severe, with a higher fever and more intense malaise. The rash of smallpox is more uniform in appearance, whereas the rash of chickenpox appears in successive waves.

3. Rash Characteristics

The rash of smallpox usually begins on the face and extremities and spreads to the trunk, with all lesions at the same stage of development. In contrast, chickenpox lesions start on the chest, back and face, spreading to other areas in successive waves, resulting in lesions at different stages.

4. Contagiousness

Both smallpox and chickenpox are highly contagious, but the period of contagiousness and mode of transmission differ. Smallpox is contagious from the onset of fever until the last scab falls off, while chickenpox is contagious from 1-2 days before the rash appears until all lesions have crusted over.

5. Scarring

Smallpox often results in deep, pitted scars, particularly on the face, whereas chickenpox usually results in superficial scars, if any, primarily due to secondary infection from scratching the blisters.

6. Mortality and Complications

Smallpox has a significantly higher mortality rate than chickenpox. It can also lead to severe complications such as encephalitis, pneumonia and blindness. Chickenpox, while generally mild, can lead to complications such as bacterial infections of the skin, pneumonia and encephalitis, especially in high-risk groups.

Characteristics and Symptoms

Smallpox and chickenpox may both present with fever and rash, but their symptoms differ in severity, pattern and appearance. Understanding these differences is key to correct diagnosis.

Smallpox Symptoms

Smallpox, caused by the variola virus, is a severe and historically devastating disease. Its symptoms include:

High Fever and Malaise: Patients experience a high fever (101–104°F), severe fatigue, headaches and muscle aches 2–4 days before the rash appears.
Rash Stages: The rash progresses uniformly through distinct stages: flat red spots (macules), raised bumps (papules), fluid-filled vesicles, pus-filled pustules and finally scabs, over 2–3 weeks.
Uniform Rash Development: All lesions are at the same stage across the body, primarily affecting the face, trunk and extremities.

Chickenpox Symptoms

Chickenpox, caused by the varicella-zoster virus, is generally milder, especially in children. Its symptoms include:

Mild Fever and Malaise: A low-grade fever (100–102°F) and mild fatigue often accompany or precede the rash.
Itchy Rash: Red spots evolve into itchy, fluid-filled blisters (vesicles) that crust over, appearing in waves over 3–5 days, mainly on the trunk, face and scalp.
Rash in Waves: Lesions appear in crops, so you’ll see spots, blisters and scabs at different stages simultaneously.

Contagiousness and Spread

Both diseases are highly contagious but differ in how they spread and for how long an infected person remains infectious.

Smallpox

Transmission: Smallpox spreads primarily through respiratory droplets from close contact, but also via contaminated objects like bedding or clothing. It’s highly contagious.
Infectious Period: Patients are contagious from the onset of fever until all scabs fall off (about 3–4 weeks), with peak contagiousness during the first 7–10 days of the rash.

Chickenpox

Transmission: Chickenpox is also highly contagious, spreading through respiratory droplets, direct contact with blister fluid or airborne particles.
Infectious Period: It’s contagious from 1–2 days before the rash appears until all lesions crust over, typically 5–7 days after rash onset.

Rash and Scarring

The appearance and after-effects of the rash differ greatly between smallpox and chickenpox, especially in terms of depth and scarring.

Smallpox

Rash: The smallpox rash consists of deep, firm pustules that eventually scab, concentrated on the face, arms and legs.
Scarring: Due to the depth and severity of the lesions, smallpox often leaves deep, disfiguring scars, especially on the face.

Chickenpox

Rash: Chickenpox produces superficial, itchy blisters that crust over, scattered across the body.
Scarring: Scarring is usually mild or absent unless the blisters are scratched or become infected, which can lead to pitted scars.

Vaccineand Prevention

Both diseases can be prevented with vaccines, though smallpox vaccination is no longer routine due to eradication.

Smallpox Vaccine

Vaccine: Smallpox was eradicated globally by 1980, thanks to a highly effective vaccine using the vaccinia virus. Routine vaccination has ceased, but stockpiles of vaccines (e.g., ACAM2000, Imvamune) are maintained for emergencies, such as bioterrorism threats.
Current Preparedness: Limited vaccination is available for high-risk groups like military personnel or lab workers. Global surveillance and rapid response plans are in place to manage potential outbreaks.

Chickenpox Vaccine

Vaccine: The varicella vaccine, given in two doses (at 12–15 months and 4–6 years), is highly effective and part of routine childhood immunization programs.
Outbreak Prevention: Vaccination significantly reduces incidence. Post-exposure vaccination within 3–5 days or varicella-zoster immune globulin (VZIG) can prevent or lessen the severity of infection in high-risk individuals.

Treatment

While no cure exists for either disease, supportive care and antivirals can reduce severity and prevent complications, especially in vulnerable patients.

Supportive Care

Both diseases rely on supportive care to manage symptoms:

Smallpox and Chickenpox: Treatment includes fever management (e.g., acetaminophen), hydration, rest and strict isolation to prevent spread.

Antiviral Options

Smallpox: No widely used antiviral exists, but tecovirimat (TPOXX) is approved for smallpox in bioterrorism scenarios. Cidofovir is another potential option.
Chickenpox: Antivirals like acyclovir, valacyclovir or famciclovir can reduce severity in high-risk groups (e.g., adults, immunocompromised individuals) if started within 24–48 hours of rash onset.

Management of Complications

Smallpox: Complications include bacterial superinfections, pneumonia and encephalitis, treated with antibiotics for secondary infections and intensive care as needed.
Chickenpox: Common complications include bacterial skin infections and, in adults, pneumonia. Rare neurological issues may occur. Antibiotics address secondary infections and severe cases may require hospitalization.

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Conclusion

Understanding the critical differences between smallpox and chickenpox

is essential for accurate diagnosis, effective treatment and appropriate public health measures.

While smallpox has been eradicated, the possibility of its use as a bioterrorism agent necessitates ongoing vigilance. Chickenpox remains a common childhood illness that can be prevented through vaccination and managed effectively with appropriate care.

A deeper understanding of these diseases helps us protect public health more effectively and take the right steps to prevent and manage potential outbreaks.

Frequently Asked Questions

Smallpox is caused by the variola virus, while chickenpox is caused by the varicella-zoster virus. Both are viral infections, but they belong to different virus families.

Smallpox causes a more uniform rash, with all the sores developing at the same time and becoming deep and firm. Chickenpox, on the other hand, produces a rash with spots in various stages (blisters, scabs, etc.) that appear in waves.

Yes, smallpox is more severe and was often fatal before its eradication. Chickenpox is generally milder, though it can lead to complications in certain individuals, especially adults or those with weakened immune systems.

Both smallpox and chickenpox are highly contagious. However, smallpox was more deadly, while chickenpox usually causes a milder illness that resolves on its own in most cases.

Yes, smallpox was eradicated globally through a successful vaccination campaign. Chickenpox can be prevented with the varicella vaccine, which significantly reduces the risk of contracting the disease.