Smallpox is a viral disease that causes pus-filled boils on the dermis. It looks similar to chickenpox, but has certain characteristic differences. Unlike chickenpox, smallpox is lethal in 30% of the cases and leaves the victim with disfiguring scars and/or blindness. Smallpox has now been eradicated through aggressive vaccination. The last case was reported in Somalia in the late 1970’s. After 2 years of worldwide surveillance, the World Health Organization (WHO) confirmed that the disease had been eradicated.
2. Causative agent
Smallpox is caused by the Variola virus, which belongs to the Orthopoxvirus genus. The members of this genus share similar genetic makeup and characteristics. Viruses belonging to this family are large and measure nearly 220-450 nm x 150-260 nm in size. DNA is the genetic material that encodes for 200 proteins, approximately, using its 200,000 base pairs. The DNA is encapsulated inside a capsid, which in turn is enveloped by membrane proteins. Two forms of the virus cause smallpox. Variola major is the most common causative agent. Variola minor induced smallpox is rare and is not severe even for pregnant women and the fetus (Jahrling, 216).
3. History of smallpox
Smallpox is thought to have made its appearance sometime around 10,000 BC in Africa and is thought to have spread to India via Egyptian merchants. Smallpox killed nearly 30% and blinded 1/3rd of the infected population. Throughout the history, it became apparent that those who survived the disease acquired lifelong immunity. As the fear of the disease grew, people resorted to the practice of variolation, which was the act of subcutaneous inoculation of the contents of a smallpox pustule into a non-infected person. However, variolation posed the risk of acquiring tuberculosis, syphilis and other blood borne diseases. It was only later when Edward Jenner developed the smallpox vaccine using the cowpox virus that eliminated the risk of infection through such blood borne diseases (Riedel, 21-24).4. Disease transmission
Smallpox is transmitted via face-to-face contact and /or exchange of infected bodily fluids with the affected individual. The disease is transmitted to a lesser extent via infected clothing and bedding. Humans are the only natural host for the virus. Therefore, there is no reservoir and the virus is not transmittable through animals or insects. The incubation period of the virus is nearly 2 weeks (7 to 17 days) during which the person is asymptomatic and non-contagious (Fenner et al., 129).5. Symptoms and diagnosis
After the incubation period, the person experiences symptoms such as fever (101 to 104°F), body ache, headache, malaise, vomiting and stomachache. At this point, the person becomes too sick to walk around and do their daily chores. This phase is called as prodrome that may last 2 to 4 days. The patient starts to feel normal after this prodrome phase only to experience the appearance of rashes in the form of red spots on the mucous lining of the mouth and on the tongue, 24 hours later. These spots rupture and release the virus into the throat. It is during this time that the rash starts appearing on the dermis of the face, arms and legs. Usually, the midsection of the body has less concentration of these spots when compared to the face and the extremities. This is the first distinguishing feature between smallpox and chickenpox. The spots transform into firm pus-filled bumps with a depression in the middle. This is the second and the most characteristic distinguishing feature of smallpox. By this time, the patient is highly contagious and experiences bouts of high fever. The rash to pustule phase lasts for about 10 days. Two weeks after the appearance of the rash, scabs start to form over the pustules. The disease is said to be abating when the scabs start to fall off, leaving a deeply pitted scar. The person is said to be non-contagious after the last of the scab falls off (Fenner et al., 129).
Earlier, laboratory test for diagnosing smallpox were limited to blood work by using tests such as a DIC panel (disseminated intravascular coagulation), platelet counts and white blood cell count. Microscopic examination of the pustules can also help identifying the virus. The collected virus could be grown in the chorioallantoic membrane of the chicken eggs for detection. Here, the virus forms the bumps typical to smallpox. In this age, many advanced techniques, such as large fragment PCR-RFLP and ELISA could be used for detection (Jahrling, 226).
In the past, the disease was said to cause blindness or death. Most of the survivors were left with disfiguring scars on the face and extremities. However, the survivors attained lifelong immunity.7. Treatment
Smallpox is treated symptomatically as there are no treatment options available once the rash start to appear. Some antiviral drugs such as cidifovir have been used against orthopox viruses with good results. Variola specific antibodies could be administered as an attempt to bring down the severity (Jahrling, 227).8. Prevention
The human race could beat smallpox and variola virus through vaccination. Since humans are the only natural reservoir, the aggressive mass vaccination worked and helped banishing the disease forever. However, vaccination has its limitation in its use in certain groups, such as pregnant women and people whose immune systems have been compromised due to preexisting illnesses (Jahrling, 229).
9. Possible use in Biowarfare
People born between the years 1980s and now are not immune against the virus. Thus, if a terrorist group were to wage a bio war using smallpox, the human race would be in grave danger. The virus, though, has been eliminated, it is still kept in 2 storages in the world. One in the United States of America and the other in Russia. If these vials were to be stolen, one could expect a very difficult battle. Some countries such as Switzerland have stored numerous vials of the smallpox vaccine to immunize if such a circumstance were to arrive (Henderson, 165).
Fenner, F., et al. "Smallpox and its eradication." Geneva: WHO (1987).
Henderson, D. A. "Smallpox virus destruction and the implications of a new vaccine." Biosecurity and bioterrorism: biodefense strategy, practice, and science 9.2 (2011): 163-168.
Jahrling, Peter B., et al. "Smallpox and related orthopoxviruses." Medical aspects of biological warfare. TMM Publications, Office of The Surgeon General, Washington, DC (2007): 215-240.
Riedel, Stefan. "Edward Jenner and the history of smallpox and vaccination." Proceedings (Baylor University. Medical Center) 18.1 (2005): 21.