Smallpox is caused by the Variola virus, belonging to the family Poxviridae, genus Orthopoxvirus. Chicken pox is NOT a member of this family of poxes. There are many poxviruses in nature, affecting species that gather in swarms and herds. There are two principal kinds of poxviruses: those of vertebrates and those of insects. To date, pox-hunters have discovered mousepox, monkeypox, skunkpox, pigpox, goatpox, camelpox, cowpox, pseudo-cowpox, buffalopox, gerbilpox, several deerpoxes, chamoispox, a couple of sealpoxes, turkeypox, canarypox, pigeonpox, starlingpox, peacockpox, sparrowpox, juncopox, mynahpox, quailpox, parrotpox, toadpox, Mongolian horsepox, Yaba money tumor pox, spectacled caiman pox, crocpox, dolphinpox, penguinpox, two kangaroopoxes, raccoonpox, and a pox called “orf.” There is also a quokkapox. (The quokka is an Australian wallaby.) At least two midgepoxes are known and grasshoppers suffer from at least six different poxes. Snakes also have the pox virus and so do fish, but nobody has done much looking for those.
Insects are also tortured with poxviruses. There are three groups of insect poxviruses: beetlepox, butterflypox (which includes mothpoxes), and flypox (including those of mosquitoes). Since insects do not have skins (they have exoskeletons), they do not develop pustules. Instead, the insect poxvirus drives them mad. For instance, a caterpillar will become nervous and stagger around in circles on a leaf. It eventually loses its balance. Its development is interrupted and it keeps growing bigger and bigger. Eventually, the insect is transformed and destroyed, leaving a swollen “bag of soup,” technically known as a “virus melt.” Also included in this soup are crystalline nuggets called “Wiffle balls.” Each opening of each wiffle ball contains a particle of insect pox which protrudes like little knobs. These wiffle balls can persist for years in the environment.
The smallpox virus consists of 186,000 base pairs of DNA that contain the information for about 187 genes. This alone makes smallpox one of the most complicated and potentially dangerous diseases known. Although smallpox was a severe and highly contagious disease, it possessed features that permitted its successful eradication.
- The disease was easily recognized and few, if any, subclinical cases occurred. This factor was a help in detection and diagnosis.
- The virus did not remain in the body as a latent infection after the patient recovered from the clinical disease.
- No regular nonhuman host could act as a reservoir of the virus.
- An effective, easily administered vaccine was available.
- The virus did not readily mutate.
The smallpox virus is a robust one that is very easily transmitted, surviving in the air for a long time. It can also survive explosive blast dissemination, making it an ideal biological warfare weapon. This concept is not new, and was used in the past by the Spanish and the Europeans to control populations in the new world. History maintains the innocence of this manoever, but there were times when it was used intentionally. The first admitted use of biological weaponry in the New World was in 1763 when blankets, contaminated with the smallpox virus, were used by the English at Fort Pitt and given to Indians loyal to the French. By the time of the First World War, biological weaponry was a skilled science, and continues unchecked today in virtually every country in the world with most refusing to admit to such a scheme.
Smallpox is known to have killed at least a third of its victims; and those who survived were left with disfiguring scars. Approximately 500 million people died of smallpox during the 1900s. This figure becomes even more startling when you consider that only 320 million died during the same period as a result of all military and civilian casualties of war, the 1918 flu pandemic, and all the AIDS deaths worldwide.
Smallpox has claimed hundreds of millions of lives between its first recorded outbreak in Ancient Egypt to its irradication in 1977. The mummy of Ramseses V shows the signs of having had the disease. A fifteen-year epidemic in the Roman Empire that began in AD165 robbed some areas of a third of its population. Crusaders brought it back from the “Holy Land.” It all but destroyed the Aztec and Inca empires after the coming of the Spaniards to the New World. It was used as a bioweapon in the new American colonies, allowing Europeans to eradicate troublesome Indians. The infamous Pocahontas died of the disease in 1617 after visiting London. It spared no class of people, causing the deaths of Queen Mary II of England in 1694, Emporer Joseph I of Austria in 1711, King Louis XV of France in 1774, Emperor Gokwomyo in 1654 and Emperor Komei in 1867. George Washington survived the disease after visiting Barbados in 1751, but remained severely scarred. The Boston Tea Party might well have been a massacre if the crew of a British ship had not been quarantined beforehand. More than 1/3 of the population of Iceland succumbed to it in 1707.
Smallpox symptoms appear about twelve days after exposure with fever, headache, and malaise. Then, a red rash will appear in the mouth and throat, as well as on the face, then later, on the arms, legs, and torso. At this stage, it can easily be confused with chickenpox. The next stage is the formation of pustules. By this time, the person is in agony, feeling as if his/her skin were on fire. The intensity of the infectiousness grows from exposure to about a week following the formation of the pustules.
The successful use of the smallpox vaccine was credited with the eradication of the disease. The vaccine was a living virus called the vaccinia virus, that caused a mild infection in the form of a single pock at the site of the inoculation. In some, especially those who had compromised immune systems, the vaccina virus spread beyond a single pock to cause moderate to severe infections. Before smallpox vaccination was discontinued in the US in 1971, about 500 children per year developed a serious vaccine-associated disease, causing some deaths.
The vaccine was developed from an old process involving scratching the skin of calves with the cowpox virus and harvesting the subsequent infection. For safety reasons, a live cowpox vaccine is no longer used. Since vaccinations ceased in the 1970s, most people are no longer immune to the disease; and those who were vaccinated more than thirty years ago have drastically reduced immunities, or none at all. Most of the world’s severely limited supply of smallpox vaccine is now more than twenty-five years old. Early in the year 2000, the US federal government finally initiated development and production of a new vaccine from cell cultures. It will be years before there is sufficient vaccine available to meet the needs should a smallpox pandemic occur.
WHO is concerned and keeping a watchful eye on any new case of smallpox since the infection might come from animals via a mutated Orthopoxvirus. The military is still being vaccinated against smallpox, even though some come down with the disease from the vaccination and then infect others who come in contact with them. The US has in store only about seventeen million doses of the vaccine.
While the vaccina virus is no longer used as a vaccine against smallpox, it is finding a possible new use in current recombinant DNA technology. Because of the nature of the poxvirus DNA, it is possible to add multiple foreign genes to this DNA, using genetic engineering methods. Thus it is possible to engineer a vaccinia virus that is able to carry antigens from a variety of different microorganisms. It is also attenuated so it cannot cause any direct illness, other than a mild single pock. Such an engineered vaccinia virus can be made stable by freeze-drying, is easier to administer, is relatively inexpensive to produce, and could be used as a vaccine against a variety of diseases that are still prevalent.