Variola

Definition

Variola Minor is also known as Variola alastrim and is another virus that causes smallpox. The English physician Edward Jenner (1749-1823) exploited the fact that cowpox created immunity to smallpox and successfully developed an attenuated (weakened) virus vaccine for smallpox.

There are two types of smallpox:

• variola major and
• variola minor.

Variola major is the more severe form and has a 30-50% fatality rate among those who are unvaccinated (3% in vaccinated persons). Variola minor has a 1-2% fatality rate in unvaccinated individuals.

Causes

Smallpox (variola) is caused by variola virus, a member of the Poxviridae family. Poxviruses are all large, ovoid, dsDNA viruses, just barely visible in the light microscope. Poxviruses are capable of causing skin lesions in a variety of animals including humans. Vaccinia is a laboratory strain of the virus used for vaccination against smallpox.

The virus usually entered the body through the respiratory (breathing) tract. It then passed through an incubation period of twelve to fourteen days. An incubation period is the time that passes after a person is infected before symptoms appear. During this time, the virus was multiplying within the body and moving through the bloodstream.

Symptoms

The initial symptoms of smallpox, 7 to 17 days after exposure, include the acute onset of fever, chills, headache, nausea, vomiting and severe muscle aches. During this time, the infected person feels fine and is not contagious. The symptoms of smallpox begin with high fever, head and body aches, and sometimes vomiting. A rash follows that spreads and progresses to raised bumps that crust, scab, and fall off after about three weeks, leaving a pitted scar. This stage generally lasts for two to four days and can be accompanied by flushing of the skin. By the fourth day of illness, the fever drops and the characteristic smallpox rash appears.

Treatment

There is no specific treatment for smallpox other than supportive care. Antiviral drugs are being developed and tested for use against smallpox. The best that could be done was to keep a patient comfortable and wait for the disease to die off on its own.

One of the best ways to prevent smallpox is through vaccination. If given to a person before exposure to smallpox, the vaccine can completely protect them. Vaccination within 3 days after exposure will prevent or greatly lessen the severity of smallpox in most people. Vaccination 4 to 7 days after exposure likely offers some protection from disease or may decrease the severity of disease. Vaccination will not protect smallpox patients who already have a rash.