Smallpox

ALSO KNOWN AS: Variola

ANATOMY OR SYSTEM AFFECTED: Gastrointestinal system, muscles, skin

DEFINITION: An acute, systemic, highly contagious disease caused by a viral infection; there are two forms, the more deadly and feared “classic” smallpox and a milder variety known as alastrim.

CAUSES: Infection with variola virus

SYMPTOMS: Rash (progressing from lesions to fluid-filled vesicles to pustules to scabs); flulike symptoms (headache, muscle aches, sometimes vomiting); complications may include blindness and sterility

DURATION: About one week

TREATMENTS: Prevention through vaccination, antiviral drugs

Causes and Symptoms

The variola virus that causes smallpox is spread through physical contact with infected victims, sometimes through droplets from nasal or oral secretions and sometimes through contact with scabs carried on bedding, towels, clothing, or other fabrics. After exposure to the variola virus, the ranges from seven to seventeen days. Early symptoms resemble influenza and include headache, muscle ache, and sometimes vomiting. When the characteristic rash appears, the infected person is already seriously ill. In unvaccinated persons not treated with antiviral medications, between 20 and 40 percent of persons infected with classic smallpox (variola major) would be expected to die. Death most often occurs between the fifth and seventh day of illness.

The initial deep-seated characteristic of smallpox develops into lesions, which then follow a progressive sequence of fluid-filled vesicles, then pustules, and finally scabs. Lesions often appear first on the face. In contrast to chickenpox, in which “crops” of lesions appear, all smallpox lesions are at the same phase in development. Smallpox cases become contagious when the first lesions appear and remain so until the last scab separates from the skin. After the scabs are completely shed, the recovered smallpox victim is left with characteristic pitted scars over large portions of the body. Some victims are rendered permanently blind as a result of contracting smallpox; men may be left sterile. Survival is generally accompanied by lifetime immunity to further infections.

Treatment and Therapy

Smallpox may be prevented through vaccination. Live virus is introduced into the skin tissue of healthy people in an effort to provide immunity against smallpox. The vaccinia virus is very similar to the variola virus that causes smallpox. Live vaccinia virus has been used for smallpox vaccinations since the time of Edward Jenner, the Englishman who pioneered in the late eighteenth century.

There is no treatment known to cure smallpox, although vaccination may be effective in lessening disease severity when administered within four days of exposure. In the 1970s, methisazone (N-methylisatin beta-thiosemicarbazone), trade name Marboran, was believed to afford some protection when administered early in the incubation period. Isolation of victims, burning all contaminated discharges, concurrent disinfection of the isolation environment, and of bedclothes and fabrics, combined with quarantine and vaccination of all persons susceptible to smallpox, has been used to contain epidemics in the historical past.

One of the last outbreaks of smallpox in the United States occurred in New York in 1947. To prevent a nationwide outbreak that year, the New York City Board of Health vaccinated about six million people (80 percent of the city’s population) within a four-week period.

The final smallpox outbreak in the United States occurred in the Rio Grande Valley of Texas in 1949. The last case reported in the Western Hemisphere was in Brazil in 1971. Prior to the official “last case” of smallpox observed in human populations in October 1977, international travelers were responsible for introducing the disease into areas where people had not received vaccinations to prevent smallpox. A laboratory accident in England in 1978 caused several cases of smallpox. In 1980, the officially declared that smallpox had been eradicated. Major world powers, including the United States and the Soviet Union, maintained stocks of viable smallpox virus for further study in labs at the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, and Novosibirsk, Russia.

Because the agreement stipulated that these two facilities would be the only ones to house samples, the public and health authorities were concerned in 2014 to learn that a government scientist had discovered a box containing six vials of smallpox virus at a lab housed in a National Institutes of Health building in Bethesda, Maryland, which had been overseen by the US Food and Drug Administration (FDA). It was reported that this cold-storage room also included vials containing viruses such as dengue and influenza as well as the rickettsia bacteria. As the most dangerous of the diseases, the fact that the smallpox virus had been left abandoned and forgotten in the lab for so many years was the most disconcerting for health officials. The vials were immediately and carefully transported to the CDC compound in Georgia as the FDA commissioner ordered a full investigation of all of the cold-storage rooms under its supervision to make sure no other samples had been overlooked; the vials had essentially been discovered because workers were clearing out the FDA lab to move to a different location. Only weeks later, the director of the CDC announced that at least two of the vials contained live smallpox virus. A label on the vial indicated that the sample had been gathered in 1954, before the eradication of the virus.

Perspective and Prospects

There are no natural carriers of smallpox virus; prior to its eradication, it was an endemic urban disease found only in humans, spread as healthy people came into contact with smallpox cases or with fabrics containing scabs shed by smallpox patients.

Following the terrorist attacks on the United States on September 11, 2001, a series of letters containing anthrax spores were sent through the US mail. These letters caused inhalation anthrax, resulting in severe illnesses and several fatalities. Governments became concerned that terrorists would attempt to cause smallpox epidemics. Within the United States, a program was initiated in 2002 to vaccinate “first responder” health professionals in the event of a bioterrorist attack using smallpox. Few people volunteered for vaccination, but among the outwardly healthy people who were vaccinated, two died unexpectedly from disease. News reports of these deaths made people who were offered vaccination less willing to participate, although subsequent study seemed to indicate that these deaths were not directly attributable to receiving the vaccine.

Few Americans, even those now involved in research on the smallpox virus, have ever seen an active case. If a bioterrorist attack using the smallpox virus were to occur, then medical personnel might have some initial difficulty identifying the disease. The general public would need to be informed about the disease in a manner that would avoid widespread panic and ensure that those exposed were immediately vaccinated and quarantined.

Prior to the mid-2010s, no medication had been approved to treat smallpox. Various antiviral agents had been investigated; the drug cidofovir (Vistide), at that time approved only to treat cytomegalovirus retinitis, was identified by several authorities as a potential agent to treat smallpox. Supportive measures that may be used include fever reducers, pain control medication, intravenous rehydration, and antibiotics to control secondary infections.

In 2014, health officials in Canada and the European Union approved the use of two vaccines to treat smallpox. Those vaccines were listed under the trade names Imvamune and Imvanex. A year later, doses of the vaccine were stored in the US Strategic National Stockpile. The US Food and Drug Administration officially approved the use of the vaccines in 2019 under the name Jynneos. A third drug called Aventis Pasteur Smallpox Vaccine (APSV) is also being stored at the Strategic National Stockpile for potential use on an emergency basis only.

The resurgence of interest in smallpox at the start of the twenty-first century brought forth many new ideas about all aspects of the disease and its prevention. In 2003, several researchers noted that the increase in numbers of people infected by human immunodeficiency virus (HIV) corresponded with the decline in smallpox vaccinations worldwide. Laboratory research has since determined that prior infection with the vaccinia virus (through vaccination) may confer some immunity to HIV.

Bibliography

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