Smallpox

. The first known cases of smallpox go back to 1350 BC and the disease has been known for a very long time. Dr. Campbell identified how smallpox is spread. Edward Jenner is credited with developing the smallpox vaccine in 1796.

There are two clinical forms of smallpox. Variola major is the severe and most common form of smallpox, with a more extensive rash and higher fever. There are four types of variola major smallpox: ordinary (the most frequent type, accounting for 90% or more of cases); modified (mild and occurring in previously vaccinated persons); flat; and hemorrhagic (both rare and very severe). Historically, variola major has an overall fatality rate of about 30%; however, flat and hemorrhagic smallpox usually are fatal. Variola minor is a less common presentation of smallpox, and a much less severe disease, with death rates historically of 1% or less.



Rash distribution:[[agent/smallpox/images/smpxman1.gif|
 * ~ Smallpox Disease ||
 * Incubation Period**
 * (Duration: 7 to 17 days)**
 * //Not contagious//** || **Exposure to the virus** is followed by an incubation period during which people do not have any symptoms and may feel fine. This incubation period averages about 12 to 14 days but can range from 7 to 17 days. During this time, people are not contagious. ||
 * Initial Symptoms //(Prodrome)//**
 * (Duration: 2 to 4 days)**
 * //Sometimes contagious*//** || The **first symptoms** of smallpox include fever, malaise, head and body aches, and sometimes vomiting. The fever is usually high, in the range of 101 to 104 degrees Fahrenheit. At this time, people are usually too sick to carry on their normal activities. This is called the //prodrome// phase and may last for 2 to 4 days. ||
 * Early Rash**
 * (Duration: about 4 days)**
 * //Most contagious//**
 * Early Rash**
 * (Duration: about 4 days)**
 * //Most contagious//**

View enlarged image]]. || A **rash emerges** first as small red spots on the tongue and in the mouth. These spots develop into sores that break open and spread large amounts of the virus into the mouth and throat. At this time, the person becomes **most contagious**. Around the time the sores in the mouth break down, a rash appears on the skin, starting on the face and spreading to the arms and legs and then to the hands and feet. Usually the rash spreads to all parts of the body within 24 hours. As the rash appears, the fever usually falls and the person may start to feel better. By the third day of the rash, the rash becomes raised bumps. By the fourth day, the bumps fill with a thick, opaque fluid and often have a depression in the center that looks like a bellybutton. (This is a major distinguishing characteristic of smallpox.) Fever often will rise again at this time and remain high until scabs form over the bumps. || The bumps become **pustules**—sharply raised, usually round and firm to the touch as if there’s a small round object under the skin. People often say the bumps feel like BB pellets embedded in the skin. || The pustules begin to form a crust and then **scab**. By the end of the second week after the rash appears, most of the sores have scabbed over. || The scabs begin to fall off, leaving marks on the skin that eventually become pitted **scars**. Most scabs will have fallen off three weeks after the rash appears. The person is contagious to others until all of the scabs have fallen off. || //**Not contagious**// || Scabs have fallen off. Person is no longer contagious. ||
 * **Pustular Rash**
 * (Duration: about 5 days)**
 * //Contagious//** ||
 * **Pustules and Scabs**
 * (Duration: about 5 days)**
 * //Contagious//** ||
 * **Resolving Scabs**
 * (Duration: about 6 days)**
 * //Contagious//** ||
 * **Scabs resolved**
 * Smallpox may be contagious during the //prodrome// phase, but is most infectious during the first 7 to 10 days following rash onset. ||
 * Smallpox may be contagious during the //prodrome// phase, but is most infectious during the first 7 to 10 days following rash onset. ||