Smallpox, also known as variola, is a very serious infectious disease caused by variola virus. It is believed that this disease has killed more people than all other infectious diseases together. Smallpox is incurable disease and only can be prevented with the help of vaccine. The last case of smallpox in the United Sates was in 1949 and in the world the last case was in 1977. However, many people are still concerned about smallpox because the virus is kept in laboratories and can be used as biological weapon.
Smallpox is caused by two variants of the virus, variola major and variola minor. Variola major produces a more serious disease and has an overall mortality rate of 30-35%. Variola minor causes a milder form of disease which kills approximately 1% of its victims.
Smallpox is contagious and can be spread from person to person during close face-to-face contact.
Symptoms of Smallpox
The incubation period of the disease is around 12 days. During the incubation period, infected person doesn’t experience any symptoms and feels healthy. During this time, infected person is not contagious. The initial symptoms are similar to influenza or common cold.
Smallpox symptoms include: Fever (at least 101 ºF) Malaise Headache Severe back pain Muscle pain Prostration Nausea VomitingAfter couple of days, the first visible lesions, small red spots, appear on mucous membranes of the mouth, tongue and throat. Day or two after, these lesions transform into small blisters filled with fluid (vesicles) and later with pus (pustules). A rash develops on the skin firstly on the forehead, than rapidly spreads to the whole face, hands, forearms, feet and finally to the trunk. Rash develops on the palms and soles. Then, the blisters start to break open and spread large amount of the virus into the mouth and throat. When the pustules open, the skin detaches from underlying layers which causes severe pain. The pustules begin to form a crust and then scab.
Difference Between Smallpox and ChickenpoxChickenpox (varicella) is the disease most frequently confused with smallpox. Still, key differences between the two diseases are: Chickenpox lesions tend to appear on the trunk and then progress to the face and extremities. Rash is rarely found on palms and soles. Chickenpox rash is superficial unlike deeply embedded rash of smallpox. Chickenpox lesions appear one after another and progress at varying rates while smallpox lesions develop and progress at the same rate. Person infected by chickenpox is contagious before the symptoms appear.