The key difference between smallpox and chickenpox and measles is their causative agents. The causative agent of smallpox is the variola virus, while the causative agents of chickenpox and measles are the varicella-zoster virus and measles virus, respectively.
Viral infections are illnesses caused by pathogenic viruses. These viral infections range from mild to deadly severe. Viral infections commonly cause respiratory and digestive illnesses and also affect the whole body. There are various viral infections, including respiratory infections, digestive system infections, viral hemorrhagic fevers, sexually transmitted infections, exanthematous infections, neurological infections, and congenital infections. Smallpox, chicken pox, and measles are exanthematous infections since they cause rashes in the skin. They give bumps or blisters on the skin surfaces and spread throughout the body.
1. Overview and Key Difference
2. What is Smallpox
3. What is Chickenpox
4. What is Measles
5. Similarities – Smallpox and Chickenpox and Measles
6. Smallpox vs Chickenpox vs Measles in Tabular Form
7. Summary – Smallpox vs Chickenpox vs Measles
What is Smallpox?
Smallpox is a serious viral infection caused by the variola virus. It is highly contagious. Initial symptoms of smallpox usually appear 12 to 14 days after exposure to the virus. The virus stays in the body from one to three weeks before causing the sickness. This period is called the incubation period. After the incubation period, several symptoms occur. Such symptoms include fever, headache, vomiting, muscle pains, severe fatigue, and severe back pains. After a few days, flat red spots appear on the skin, starting from the mouth and then spreading throughout the skin.
Smallpox affects the face, arms, and legs first. Within one or two days, the small spots turn into small blisters with clear fluid. These are called pustules. Scabs form after eight to nine days later and fall off, leaving permanent scars. Smallpox spreads directly from person to person, indirectly from an infected person, or through contaminated items. Most people affected by the smallpox virus survive; however, rare types of this virus are deadly. Such severe forms are common in children and pregnant women. Two vaccines are available against the smallpox virus. The ACAM2000 vaccine uses a live virus, and the Jynneos vaccine consists of a very weak strain of the virus.
What is Chickenpox?
Chickenpox is a viral infection caused by the varicella-zoster virus (VZV). It mainly affects children and is highly contagious to people who have not had the infection previously or have been vaccinated against it. Chickenpox causes an itchy rash with small blisters. These blisters appear 10 to 21 days after exposure to the virus and last about 10 days. Other symptoms include fever, headache, loss of appetite, tiredness, and malaise. Generally, the chickenpox rash goes through three phases. The first phase gives out raised pink or red papules, which break after several days. The second phase forms small fluid-filled blisters that break and leak. The third phase forms crusts and scabs covering the broken blisters. It takes a few days for the healing process.
Chickenpox virus spreads within 48 hours before the rash appears and remains contagious until the broken blisters are crusted. The infection is usually mild in children. The virus is spread through direct contact or chicken pox coughs and sneezes. Chickenpox is usually a mild disease; however, it leads to complications such as bacterial infections, pneumonia, dehydration, encephalitis, toxic shock syndrome, Reye’s syndrome, or even death. Newborns, infants, adults, pregnant women, immunocompromised patients, or patients taking steroid medications are at a higher risk. The chickenpox or Varicella vaccine is the best and most effective way for the prevention of infection.
What is Measles?
Measles is a contagious viral infection caused by the measles virus. It is mainly found in the nose and throat of an infected patient. Measles is also known as rubeola. It is an acute viral respiratory viral illness. Measles easily spreads due to the spraying of droplets into the air by measles coughs, sneezes, and speech. The droplets remain in the air for about an hour and also land on surfaces where they are able to live for several hours. Measles is highly contagious from about four days before to after the rash appears. Therefore, people without vaccination against measles are more prone to measles viral infection. International travelers and people with vitamin A deficiency are also under the risk category of measles. Symptoms of measles appear around 10 to 14 days after exposure to the virus.
Symptoms include fever, runny nose, dry cough, sore throat, skin rashes, Koplik’s spots, and conjunctivitis. The infection takes place in stages over two to three weeks. Complications of measles include vomiting, diarrhea, ear infections, bronchitis, laryngitis, pneumonia, encephalitis, and pregnancy problems in women. The best preventive measure for measles is the measles vaccine, which is a combination vaccine and it is called measles-mumps-rubella (MMR). MMR is usually given between 12 to 15 months of age and again between four to six years of age.
What are the Similarities Between Smallpox and Chickenpox and Measles?
- Smallpox, chicken pox, and measles are viral infections.
- They are highly contagious.
- All three infections give rashes.
- They have common symptoms, such as fever and headaches.
- Moreover, all affect the skin.
- All have an incubation period of about 10 to 14 days.
- All are prevented by vaccination.
- Easily spread through air droplets.
What is the Difference Between Smallpox and Chickenpox and Measles?
Smallpox is caused by the variola virus, chickenpox is caused by the varicella-zoster virus, and measles is caused by the measles virus. Thus, this is the key difference between smallpox and chickenpox and measles. Fever in smallpox usually occurs one to three days before the appearance of a rash, while in chickenpox, fever takes place one to two days. In measles, fever occurs three to five days before the rash. Moreover, lesions appear in one stage during smallpox, while they appear in multiple stages in chickenpox and measles.
The below infographic presents the differences between smallpox and chickenpox and measles in tabular form for side-by-side comparison.
Summary – Smallpox vs Chickenpox vs Measles
Smallpox, chickenpox, and measles are contagious viral infections. Smallpox is caused by the variola virus while chickenpox is caused by the varicella-zoster virus, and measles is caused by the measles virus. During smallpox, the rash develops on the skin, starting from the face and spreading slowly. Fever is usually caused one to three days before the rash. In chickenpox, the rash develops throughout the body and spreads rapidly. Fever usually occurs one to two days before the rash. During measles, the rash develops from the face and spreads rapidly. Fever takes place three to five days before the rash. So, this summarizes the difference between smallpox and chickenpox and measles.
1. “Chickenpox.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 8 May 2021.
2. “Measles.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 11 May 2022.
3. “Smallpox.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 5 Aug. 2022.
1. “Smallpox versus chickenpox english plain” By Smallpox (variola orthopox virus) Early Rash vs chickenpox.gif: (Public Domain) via Commons Wikimedia
2. “Chickenpox Adult back” By F malan – Own work (CC BY-SA 3.0) via Commons Wikimedia
3. “Measles” By Dave Haygarth (CC BY 2.0) via Flickr