Smallpox

Smallpox is an infection caused by the virus called variola, a member of the poxvirus family. Throughout all of history, smallpox has been a greatly feared disease, responsible for huge epidemics worldwide, and the cause of great suffering and massive numbers of deaths. In 1980, the World Health Organization (WHO) announced that an extensive program of vaccination against the disease had resulted in the complete eradication of the virus, with the exception of samples of stored virus in two laboratories.

Description

Smallpox was strictly an infection of human beings. Animals and insects could neither be infected by smallpox, nor carry the virus in any form. Most infections were caused by contact with a person who had already developed the characteristic skin lesions (pox) of the disease, although a person who had a less severe infection (not symptomatic or diagnosable in the usual way) could unwittingly spreading the virus.

Causes and symptoms

Smallpox was a relatively contagious disease, which accounts for its ability to cause massive epidemics. The variola virus was acquired from direct contact with individuals sick with the disease, from contaminated air droplets, and even from objects used by another smallpox victim (books, blankets, utensils, etc.). The respiratory tract was the usual entry point for the variola virus into a human being.

After the virus entered the body, there was a 12–14 day incubation period during which the virus multiplied, although no symptoms were recognizable. After the incubation period, symptoms appeared abruptly and included fever and chills, muscle aches, and a flat, reddish purple rash on the chest, abdomen, and back. These symptoms lasted about three days, after which the rash faded and the fever dropped. A day or two later, fever would return, along with a bumpy rash starting on the feet, hands, and face. The rash would progress, ultimately reaching the chest, abdomen, and back. The individual bumps (papules) would fill with clear fluid, and eventually become pus-filled over the course of 10–12 days. These pox would eventually scab over, each leaving a permanently scarred pock or pit when the scab dropped off.

Death from smallpox usually followed complications such as bacterial infection of the open skin lesions, pneumonia, or bone infections. A very severe and quickly fatal form of smallpox was called "sledgehammer smallpox," and resulted in massive, uncontrollable bleeding (hemorrhage) from the skin lesions, as well as from the mouth, nose, and other areas of the body.

Fear of smallpox came from both the epidemic nature of the disease, as well as from the fact that no therapies were ever discovered to either treat the symptoms of smallpox, or shorten the course of the disease.

Diagnosis

In modern times, prior to the eradication of the variola virus, a diagnosis of smallpox could be made using an electron microscope to identify virus in fluid from the papules, urine, or in the patient's blood prior to the appearance of the papular rash.

Treatment

Treatment for smallpox was only supportive, meaning that the only treatment available was aimed at keeping a patient as comfortable as possible. No treatments were ever found that would halt the progression of the disease.

Prognosis

Death from smallpox ranged up to about 35%, with the more severe, hemorrhagic form nearly 100% fatal. Patients who survived smallpox infection nearly always had multiple areas of scarring where each pock had been.

Prevention

From about the tenth century in China, India, and the Americas, it was noted that individuals who had had even a mild case of smallpox could not be infected again. Fascinating accounts appear in writings from all over the world of ways in which people tried to vaccinate themselves against smallpox. Material from people ill with smallpox (fluid or pus from the papules, scabs over the pox) was scratched into the skin of people who had never had the illness, in an attempt to produce a mild reaction and its accompanying protective effect. These efforts often resulted in full-fledged smallpox, and probably served only to help effectively spread the infection throughout a community. In fact, such crude smallpox vaccinations were against the law in Colonial America.

In 1798, Edward Jenner published a paper in which he discussed his important observation that milkmaids who contracted a mild infection of the hands (called cowpox, and caused by a relative of the variola virus) appeared to be immune to smallpox. Jenner created an immunization against smallpox that used the pus found in the lesions of cowpox infection. Jenner's paper led to much work in the area of vaccinations, and ultimately resulted in the creation of a very effective vaccination against smallpox which utilized the vaccinia virus, another close relative of variola.

In 1967, WHO began its attempt to eradicate the smallpox virus worldwide. The methods used in the program were simple:

• Careful surveillance for all smallpox infections worldwide, to allow for quick diagnosis and immediate quarantine of patients.
• Immediate vaccination of all contacts diagnosed with infection, in order to interrupt the virus' usual pattern of infection.

The WHO's program was extremely successful, and the virus was declared to have been eradicated worldwide in May of 1980. Today, two laboratories (in Atlanta,

Smallpox pustules on the arm of an Asian Indian man. (Photograph by C. James Webb, Phototake NYC. Reproduced by permission.)

Georgia, and in Moscow, Russia) retain samples of the smallpox virus. These samples, as well as stockpiles of the smallpox vaccine, are stored because some level of concern exists that another poxvirus could undergo genetic changes (mutate) and cause human infection. Other areas of concern include the possibility of smallpox virus being utilized in biological warfare, or the remote chance that smallpox virus could somehow escape from the laboratories where it is stored. For these reasons, surveillance continues of various animal groups that continue to be infected with viruses related to the variola virus, and large quantities of vaccine are stored in different countries around the world, so that response to any future threat by the smallpox virus could be prompt.