Variola virus of smallpox

Poxviruses that cause disease in humans belong to four different genera of the vertebra poxvirus subfamily. The majority these viruses belong to the genus Orthopoxvirus.

Poxviruses were first visualized by electron microscopy in 1938. The genus Orthopoxviruses comprises many related viruses and includes, in addition to variola major, vaccinia, virus, cowpox, monkeypox, ectromelia, camelpox, taterapox, Uasin Gishu disease and racoonpox.

The orthopoxvirus Variola virus is the only member species of the Orthopoxvirus genus which is a solely human pathogen.

Variola virus, like all orthopoxviruses, replicates solely in the cytoplasm of infected cells. At least two types of Variola virus have been clearly described that have distinct biological and genetic properties and different human clinical and epidemiological manifestation.

These have been described as variola major and Variola minor. Another variant has been suggested, intermedius.

The virion of Variola virus has the same size and shape as that of all other orthopoxviruses.

The most important property of variola virus, in relations its effects on the human host, is its virulence. Some epidemics of smallpox were associated with high mortality and other with a low mortality.

The genetic difference between the variola strains most likely reflects differences in their replication and host-cell assembly leading to a greater or lesser virulence.
Variola virus of smallpox

Infectious disease of smallpox

One of the most devastating diseases to ever strike civilization is smallpox. It is an infection that is highly contagious or easily spread from person to person.

The scientific name of the virus is Variola. Smallpox virus is shaped like a brick and covered with little spiky bits. In smallpox virus, there are a hundred different proteins protecting a strand of DNA combating 187 genes.

The smallpox virus comes in two types: the deadly Variola major and a less dangerous virus called Variola minor. About 30 percent of those who contracted Variola major died.

Smallpox spreads from human to human through the air via breathing, sneezing or coughing. People who got small pox had tiny little bumps all over their bodies.

The virus can also be spread though contact with an infected personal bodily fluids or by touching items that person has contaminated.

The virus disseminates through the body via the lymph and blood, At this point in the infections process, few symptoms of disease are apparent and patients generally fell well.

People with smallpox were moist infectious from the onset of their papulor rash through the first 7 to 10 days of the rash.

Approximately 30 percent of susceptible in contacts come down with the disease. As scabs formed, respiratory infectivity waned, but patients were considered infectious until all scabs separated.
Infectious disease of smallpox