Statistics Of Smallpox

[Egisto Chancellor]

Thousandsof years ago, variola virus (smallpox virus) emerged and began causing illness and deaths in human populations, with smallpox outbreaks occurring from time to time. Thanks to the success of vaccination, the last natural outbreak of smallpox in the United States occurred in 1949. In 1980, the World Health Assembly declared smallpox eradicated (eliminated), and no cases of naturally occurring smallpox have happened since.

Smallpox research in the United States continues and focuses on the development of vaccines, drugs, and diagnostic tests to protect people against smallpox in the event that it is used as an agent of bioterrorism.

Smallpox is an acute contagious disease caused by variola virus, a member of the Orthopoxvirus family. Smallpox, which is believed to have originated over 3,000 years ago in India or Egypt, was one of the most devastating diseases known to humanity. Smallpox is transmitted from person to person by infected aerosols and air droplets spread in face-to-face contact with an infected person. The disease can also be transmitted by contaminated clothes and bedding, though the risk of infection from this source is much lower.

In 1967, WHO launched an intensified plan to eradicate smallpox. Following a successful campaign to achieve high levels of immunization globally, the last case of endemically circulating smallpox occurred in 1977. In 1979, WHO recommended that vaccination against smallpox be stopped in all countries, the only exception being special groups, such as researchers working with smallpox and related viruses.

The global eradication of smallpox was certified in December 1979 and endorsed by the World Health Assembly in 1980, marking one of the most successful collaborative public health initiatives in history. Following eradication, smallpox, vaccine production was halted. A large stock of the smallpox vaccine was retained around the world although the storage conditions and potency of these stocks are not known. Two sites in the USA and Russia hold stocks of variola virus. In the interest of global security, these stocks were to be destroyed by the end of the twentieth century. However, due to continued interest in research and development involving variola virus, the destruction of the remaining stocks of smallpox virus has been postponed by the World Health Assembly.

Edward Jenner demonstrated, in 1798, that inoculation of humans with live vaccinia virus (cowpox) could protect against smallpox. This brought the first hope that the disease could be controlled. Vaccinia vaccine has been used continuously since then. Most existing vaccine stocks and the vaccine utilized by the WHO eradication campaign consisted of pulp scraped from vaccinia-infected animal skin, mainly calf or sheep, with phenol added to a concentration sufficient to kill bacteria, but not so high as to inactivate the vaccinia virus. The live vaccine was then freeze-dried and sealed in ampoules for later re-suspension in sterile buffer and subsequent intradermal inoculation by multiple puncture with a bifurcated needle. The vaccinia virus is remarkably stable when lyophilized, and vaccines stored under appropriate conditions for as long as 18 years have not lost their potency.

WHO recommendations for the production and quality control of smallpox vaccines were first adopted in 1959 and revised in 1965. They were updated in 2003 in case new supplies of vaccine were required. This update includes production on cell substrates and introduces modern requirements for adventitious agent testing.

Smallpox is an acute contagious disease caused by the variola virus, a member of the orthopoxvirus family. It was one of the most devastating diseases known to humanity and caused millions of deaths before it was eradicated. It is believed to have existed for at least 3000 years.

The smallpox vaccine, created by Edward Jenner in 1796, was the first successful vaccine to be developed. He observed that milkmaids who previously had caught cowpox did not catch smallpox and showed that a similar inoculation could be used to prevent smallpox in other people.

Early symptoms of smallpox include high fever, fatigue and severe back pain, and less often, abdominal pain and vomiting. Two to 3 days later the virus produces a characteristic rash with bumps full of a clear liquid, which later fill with pus and finally develop a crust that dries and falls off. The rash begins on the face and hands, then spreads to the rest of the body. Lesions develop in the mucous membranes of the nose and mouth and ulcerate soon after formation.

The WHO Smallpox Secretariat based in WHO Headquarters coordinates all smallpox eradication-related and post-eradication activities. These include overseeing permitted research with live variola virus for the development of countermeasures such as vaccine and antivirals. Since the eradication era, safer vaccines and specific treatments have been developed for smallpox and related diseases such as monkeypox. The Secretariat is also responsible for emergency preparedness and manages a smallpox vaccine emergency stockpile in the unlikely event that the disease re-emerges. The Secretariat manages the biosafety and biosecurity inspections of the authorized variola virus repositories as mandated by the World Health Assembly, and ensures annual reporting to WHO Governing Bodies. The Smallpox Secretariat supports WHO Archives in preserving the global history of smallpox and documenting the lessons learned from successful eradication of smallpox.

Characterized by fever and a distinctive type of rash, smallpox was once one of the leading health threats facing the human species. Caused by a virus, smallpox used to kill up to a third of the people who developed the illness.

However, by 1980, smallpox was effectively eliminated as a public health concern, thanks to a major campaign conducted by the World Health Organization. The last known case - anywhere in the world - was reported in the late 1970s. Since no animals other than humans are known to carry or transmit smallpox, the risk of getting the illness had effectively been reduced to zero.

Unfortunately, smallpox may not be completely behind us. A few samples of the smallpox virus were kept for laboratory use after the illness was eradicated - and there is now reason to believe that the virus may have been adapted for use as a weapon. The possibility of a smallpox outbreak, caused by a deliberate release of the virus, is now regarded as a real possibility. The likelihood of a terrorist attack using smallpox is thought to be very low. However, the consequences of such an attack - if it did occur - would be very serious.

The symptoms of smallpox begin with a high fever, head and body aches and, in some cases, vomiting. After two to four days, a rash appears. The rash spreads, and develops into raised bumps that crust and scab over. After about three weeks, the scabs fall off, leaving pitted scars.

The first symptoms of smallpox usually show up about 12-14 days after a person has been exposed to the illness, although symptoms can take as little as seven days or as long as 17 days to appear. Once the first symptoms appear, the patient is usually too ill to travel or engage in most forms of activity. The patient doesn't become infectious - capable to transmitting the disease to others - until the rash appears.

Smallpox is contagious, but it's spread less easily than illnesses like influenza or measles. Generally, it takes prolonged, face-to-face contact - of the kind that takes place in a household setting - to spread the disease from one person to another. It can also be spread through direct contact with body fluids, or objects like bedding and clothing. It can also be spread through the air in buildings or other enclosed spaces, although that happens less commonly.

However, the vaccine can cause serious, potentially fatal reactions in some people, so the benefits of vaccination need to be balanced against the risks. At a minimum, it's been estimated that roughly one out of every million people who receive the vaccine will die - and 15 will become very seriously ill. And unless someone does use the disease as a weapon, the risk of becoming ill with smallpox is zero.

Institute of Medicine (US) Board on Health Promotion and Disease Prevention. Scientific and Policy Considerations in Developing Smallpox Vaccination Options: A Workshop Report. Washington (DC): National Academies Press (US); 2002.

The last case of naturally occurring smallpox occurred almost 25 years ago, and 24 years ago the last episode occurred in Birmingham, England, with the laboratory escape of variola virus. As a result of its eradication, virtually all clinicians, particularly in northern countries, are unfamiliar with this disease and research on human smallpox has practically stopped. Eradication was relatively easy to achieve because humans are the only reservoirs and vectors, the disease is clinically manifest, and there is no carrier or latent state. Moreover, one episode gives lifelong protection, transmission occurs when the disease is manifest, there is a stable vaccine, and it is relatively straightforward to trace chains of transmission.

Conditions that resemble the maculopapular eruptions of smallpox include drug eruptions, measles, secondary syphilis, and vaccine reactions. Chickenpox, monkeypox, and generalized vaccinia can resemble the papulovesicular eruptions of smallpox. With newer molecular approaches to diagnosis, however, more rapid and precise screening, if not confirmation, of variola and chicken pox can help in diagnosis. However, cell culture is the only reliable diagnostic tool for the orthopoxes when the clinical symptoms are indistinguishable.

Smallpox is transmitted person-to-person by large airborne droplets, that is, face-to-face contact of 2 to 2.5 meters. Thus homes and hospitals are major transmission sites. However, carriers are symptomatic so investigations done with due diligence can prevent further spread. In general, it has been believed that smallpox can not be carried by the wind and travel great distances, although outbreaks in hospitals might have been due to movement of the virus through air ducts.

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