Smallpox (also known by the Latin names Variola or Variola vera) is a highly contagious disease unique to humans. It is caused by two virus variants called Variola major and Variola minor. V. major is the more deadly form, with a typical mortality of 20-40 percent of those infected. The other type, V. minor, only kills 1% of its victims. Many survivors are left blind in one or both eyes from corneal ulcerations, and persistent skin scarring - pockmarks - is nearly universal. Smallpox was responsible for an estimated 300-500 million deaths in the 20th century. As recently as 1967, The World Health Organization (WHO) estimated that 15 million people contracted the disease and that two million died in that year.
After successful vaccination campaigns, the WHO in 1979 declared the eradication of smallpox, though cultures of the virus are kept by the Centers for Disease Control and Prevention (CDC) in the United States and at the Institute of Virus Preparations in Siberia, Russia. Smallpox vaccination was discontinued in most countries in the 1970s as the risks of vaccination include death (~1 per million), among other serious side effects. Nonetheless, after the 2001 anthrax attacks took place in the United States, concerns about smallpox have resurfaced as a possible agent for bioterrorism. As a result, there has been increased concern about the availability of vaccine stocks. Moreover, President George W. Bush has ordered all American military personnel to be vaccinated against smallpox and has implemented a voluntary program for vaccinating emergency medical personnel.
Smallpox virus preferentially attacks skin cells and by days 14-15, smallpox infection becomes obvious. The attack on skin cells causes the characteristic pimples associated with the disease. The pimples tend to erupt first in the mouth, then the arms and the hands, and later the rest of the body. At that point the pimples, called macules, should still be fairly small. This is the stage at which the victim is most contagious.
By days 15-16 the condition worsens and the pimples grow into papules. These then fill up with pus, turning them into pustules. After the appearance of the pustules, the course of the disease can take two vastly different courses. In route A -- if the victim is going to survive the outbreak -- the pustule will deflate in time (the duration is variable), and will start to dry up, usually beginning on day 28. Eventually the pustules will completely dry and start to flake off. Once all of the pustules flake off, the patient is considered cured. If the patient is going to die, route B, an entirely different set of symptoms starts to develop. First, bleeding will occur under the skin, making the skin look charred and black (this is known as black pox). Soon afterwards, bleeding begins in the organs. Death may occur from bleeding, or from loss of fluid. The entry of other infectious organisms, since the skin and intestine are no longer a barrier, can also lead to multi-organ failure.
Infection by Smallpox
Transmission is by droplets, and infection in the natural disease will be via the lungs. The incubation period to obvious disease is around 12 days. In the initial growth phase the virus seems to move from cell to cell, but around the 12th day, lysis of many infected cells occurs and the virus will be found in the bloodstream in large numbers. The initial or prodromal symptoms are essentially similar to other viral diseases such as influenza and the common cold - fevers, muscle pain and stomach aches etc. The digestive tract is commonly involved, leading to vomiting. Most cases will be prostrated.
Posted by Staff at May 17, 2005 3:34 AMblog comments powered by Disqus