Variola major

Overview

Variola major is a highly contagious and deadly virus that is responsible for causing smallpox. It is part of the Orthopoxvirus genus, which also includes viruses like cowpox and monkeypox. Variola major is a DNA virus with a complex structure and life cycle. It has been responsible for several pandemics throughout history, leading to millions of deaths worldwide.

Close-up view of Variola major virus under a microscope.

History

The history of Variola major is intertwined with the history of smallpox, as it is the primary causative agent of the disease. Smallpox has been a known disease for thousands of years, with evidence of the disease found on Egyptian mummies dating back to the 3rd century BCE. The disease was widespread and deadly, with outbreaks occurring regularly throughout history.

Structure and Life Cycle

Variola major is a large, brick-shaped virus with a complex structure. It is a DNA virus, meaning its genetic material is made up of deoxyribonucleic acid. The virus enters the host cell and uses the cell's machinery to replicate itself. The newly formed viruses then leave the host cell, often killing it in the process, and go on to infect other cells.

Transmission

Variola major is highly contagious and is primarily transmitted from person to person through respiratory droplets. When an infected person coughs or sneezes, they release droplets containing the virus into the air. These droplets can then be inhaled by a nearby person, leading to infection.

Symptoms and Complications

The symptoms of Variola major infection typically begin with a high fever, severe headache, and backache. This is followed by the development of a characteristic rash, which progresses to raised bumps and then to pus-filled blisters. The blisters eventually scab over and fall off, often leaving deep, pitted scars.

Treatment and Vaccination

There is no specific treatment for Variola major infection. Management of the disease primarily involves supportive care, including hydration and pain management. Vaccination with the smallpox vaccine can prevent infection if given within a few days of exposure to the virus.

Eradication

The World Health Organization launched an intensive global smallpox eradication campaign in 1967. By 1980, the disease was declared eradicated, making it the first disease to be eradicated by human effort. Today, the only known samples of Variola major are stored in two laboratories – one in the United States and one in Russia.