Variola Virus: Symptoms, Causes, Types, Diagnosis, and Treatments
Variola virus is a historically significant virus responsible for causing smallpox, a devastating disease that once caused widespread mortality and suffering worldwide. Although smallpox was declared eradicated by the World Health Organization (WHO) in 1980, the study of Variola-virus remains important in virology, epidemiology, and biosecurity. This article explores everything you need to know about the Variola-virus, including its symptoms, causes, types, diagnosis, and available treatments.
What is the Variola Virus?
Variola virus is a member of the Orthopoxvirus genus within the Poxviridae family. It is a large, double-stranded DNA virus that exclusively infects humans. The virus causes smallpox, a contagious and often fatal disease characterized by fever and a distinctive progressive skin rash.
Historical Background
Smallpox has affected humanity for thousands of years, with evidence dating back to ancient Egypt and India. It was responsible for millions of deaths until widespread vaccination efforts led to its eradication. The Variola-virus is the only virus to have been completely eradicated from nature by human effort.
Causes of Variola Virus Infection
The Variola virus spreads primarily through direct and prolonged face-to-face contact with infected individuals. It is transmitted via respiratory droplets when an infected person coughs or sneezes. It can also spread through contact with contaminated objects such as bedding or clothing.
Transmission Modes
- Respiratory Droplets: The main route, especially in close quarters.
- Fomites: Contact with objects contaminated with the virus.
- Rarely, via aerosolized particles in confined spaces.
Because Variola-virus is highly contagious and stable in the environment, outbreaks historically spread quickly, especially in densely populated areas.
Types of Variola Virus
There are two main types of Variola virus that caused distinct forms of smallpox:
1. Variola Major
- This is the more severe form of the virus.
- It accounts for approximately 90% of smallpox cases historically.
- The case fatality rate ranged between 20% to 40%, depending on the strain and population affected.
- Symptoms are more intense with extensive rash and severe systemic illness.
2. Variola Minor
- A less severe form causing milder disease.
- Also called alastrim.
- Fatality rate was less than 1%.
- Often associated with a milder rash and faster recovery.
Symptoms of Variola Virus Infection
The clinical presentation of smallpox due to Variola virus infection develops in stages. The incubation period ranges from 7 to 17 days, during which the infected person shows no symptoms.
Early Symptoms (Prodromal Phase)
- High fever (up to 40°C/104°F)
- Severe fatigue and malaise
- Headache
- Backache and muscle pain
- Vomiting
- Severe abdominal pain (in some cases)
- Sore throat and cough
Rash Development
After 2 to 4 days of initial symptoms, a characteristic rash appears, usually starting on the face, hands, and forearms before spreading to the trunk.
- Macules: Flat, red spots.
- Papules: Raised bumps.
- Vesicles: Fluid-filled blisters.
- Pustules: Pus-filled, round, firm lesions that become crusted.
- The rash progresses synchronously, meaning all lesions evolve at the same rate.
Other Signs
- Lesions are often painful.
- Scabs eventually form and fall off, leaving scars.
- In severe cases, complications such as pneumonia, encephalitis, and sepsis may occur.
Diagnosis of Variola Virus Infection
Since smallpox has been eradicated, clinical diagnosis today is primarily theoretical or for laboratory preparedness. However, diagnosis traditionally included:
Clinical Examination
- Identification of the characteristic rash pattern.
- Patient history, including exposure risk and symptom timeline.
Laboratory Tests
- Polymerase Chain Reaction (PCR): Detects Variola-virus DNA with high specificity.
- Electron microscopy: Visualizes the virus particles.
- Virus isolation: Grown in cell cultures for confirmation (restricted to high-containment labs).
- Serological tests: Detect antibodies against Orthopoxviruses.
Differential Diagnosis
Because smallpox rash can resemble other diseases, it’s important to distinguish it from:
- Chickenpox (Varicella-Zoster Virus)
- Monkeypox
- Herpes simplex virus infections
- Syphilis
- Measles
Treatment of Variola Virus Infection
There is no proven antiviral cure for smallpox caused by Variola virus. Treatment was primarily supportive and symptomatic to reduce mortality and complications.
Supportive Care
- Hydration and nutrition management.
- Fever and pain control.
- Treatment of secondary bacterial infections with antibiotics.
- Isolation of infected patients to prevent spread.
Antiviral Agents
Though no antiviral was specifically developed for Variola-virus, several drugs show promise:
- Tecovirimat (TPOXX): Approved for treatment of Orthopoxvirus infections. It inhibits the viral envelope protein, blocking virus spread.
- Cidofovir and Brincidofovir: Broad-spectrum antivirals effective in vitro against poxviruses.
- These drugs are stockpiled as part of biodefense measures.
Vaccination
- Smallpox vaccine (based on Vaccinia virus) is the primary prevention method.
- Vaccination can also be used post-exposure, within 3-4 days, to reduce severity.
- Routine vaccination ended after eradication, but some countries maintain stockpiles.
Prevention and Control Measures
Because Variola virus is eradicated, prevention mainly focuses on biosecurity:
- Strict laboratory containment of Variola-virus stocks.
- Monitoring and rapid response plans for possible bioterrorism events.
- Research into improved vaccines and antivirals.
Variola Virus in Modern Times
Though smallpox no longer occurs naturally, Variola virus is retained in two WHO-designated repositories in high-security laboratories in the U.S. and Russia. There is ongoing debate about whether to destroy these stocks, balancing research benefits against security risks.
Summary
Variola-virus is a highly contagious and deadly virus historically responsible for smallpox. Despite eradication, its study remains crucial for understanding viral diseases, vaccine development, and biosecurity. Recognizing the symptoms, knowing the types, accurate diagnosis, and potential treatments ensures preparedness against any future threats related to this virus.
Frequently Asked Questions (FAQs) About Variola Virus
What is the Variola virus?
The Variola virus is a member of the Orthopoxvirus family and is the virus responsible for causing smallpox, a highly contagious and sometimes fatal disease.
How is the Variola virus transmitted?
It spreads mainly through respiratory droplets during close, face-to-face contact, as well as through contact with contaminated objects like bedding or clothing.
What are the main symptoms of a Variola virus infection?
Symptoms begin with fever, fatigue, and headache, followed by a characteristic rash that progresses from macules to pustules and crusts.
How many types of Variola virus exist?
There are two main types: Variola major, which causes severe smallpox, and Variola minor, which results in a milder form of the disease.
Is the Variola virus still a threat today?
Smallpox was declared eradicated in 1980, so naturally occurring infections no longer exist. However, Variola virus is studied for biosecurity reasons and preparedness against potential bioterrorism.
How is smallpox diagnosed?
Diagnosis involves clinical examination of the rash, patient history, and laboratory tests like PCR to detect viral DNA.
Can the Variola virus infect animals?
No, Variola virus exclusively infects humans and has no known animal reservoirs.
What treatments are available for Variola virus infections?
There is no specific cure, but antiviral drugs like Tecovirimat show promise. Supportive care and vaccination are key to managing and preventing the disease.
How effective is the smallpox vaccine against Variola virus?
The vaccine is highly effective, providing immunity that can prevent or reduce the severity of infection if given before or shortly after exposure.
How long does the incubation period last for Variola virus?
Symptoms typically appear 7 to 17 days after exposure, during which the infected person is not contagious.
What makes Variola major more dangerous than Variola minor?
Variola major causes more severe illness and has a higher fatality rate (20-40%) compared to Variola minor’s milder symptoms and less than 1% fatality rate.
Why was smallpox eradication considered a major achievement?
Smallpox was the first and only human disease eradicated globally through coordinated vaccination efforts, saving millions of lives.
Can smallpox re-emerge in the future?
Since natural reservoirs no longer exist and vaccination stopped, re-emergence is highly unlikely unless through accidental or intentional release from laboratory stocks.
What safety measures exist for handling Variola virus samples today?
Samples are kept under strict biosecurity in two WHO-approved labs with high-containment protocols to prevent accidental release.
How does Variola virus differ from other poxviruses like monkeypox?
While both cause similar symptoms, Variola virus causes smallpox exclusively in humans and is eradicated, whereas monkeypox can infect animals and still causes sporadic human cases.
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