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Smallpox - ancient scourge or modern threat?

Liz Rosies
RGN MSc(TravelMed)
Travel Health Advisor
Author of

Before its eradication in 1979, smallpox had been around for many thousands of years. The earliest evidence of the disease was found on the mummified body of an Egyptian pharaoh who died in 1157 BC. From Egypt the disease is believed to have been carried by traders to India and across the globe. With the help of the crusaders in the 11th and 12th centuries, smallpox arrived in Europe.(1)
It was in 1796 that Edward Jenner had a major breakthrough in his effort to fight the virus, when he discovered the smallpox vaccine. From the early 1800s the smallpox vaccine was used in a random manner, but it was finally adopted by the WHO for a global eradication programme in 1956.(2)
The last known case of smallpox was recorded in 1977 in Somalia, with global eradication announced in 1980. Following the WHO's official certified eradication, efforts were made to minimise the number of laboratories holding the variola virus, which causes smallpox. Existing supplies of the virus were sent to one of two secure laboratories, one in Russia, one in the USA. However, due to the increased risk of global terrorism some governments believe that stocks of the variola virus, which could be used to cause deliberate harm, still exist elsewhere around the globe.(3) While it is not possible to verify such claims, this has led to the need for governments to adopt contingency plans should such a threat exist.
What is smallpox?
Smallpox is a viral disease caused by the variola virus, of which humans are the only known host. The word smallpox comes from a Latin word meaning "spotted", which describes the main feature of the disease - raised bumps or spots on the face and body.(4)
Smallpox is an airborne disease, transmitted by direct face-to-face contact with an infected person.(5) Transmission does not occur among animals. In the event of a terrorist attack it is speculated that transmission could occur by breathing in the virus.
Following infection the incubation period usually lasts 7-14 days. During this period a person is not ­contagious. The first signs of the disease include general flu-like symptoms, such as a high fever, aches and vomiting. This phase of the disease is referred to as the prodromal phase and can last up to four days.(6)
After one to four days a rash appears. The rash initially appears as small red spots on both the mouth and tongue, which develop into sores. From this time until the final smallpox scab falls off, that person is contagious. Within 24 hours the rash spreads over the entire body, forming raised bumps that characteristically look like the middle of a belly button. From about day five onwards the raised bumps fill with a fluid and eventually become hard, and these are known as pustules. The pustules will crust and scab by approximately day 14. As already stated, the person remains contagious until the final scab has fallen off - which occurs at approximately day 15.(7) When smallpox occurs in an unvaccinated, nonimmune population the fatality rate is approximately 30%.(8)
Smallpox vaccination
While the use of new antiviral drugs, developed during the last century, might have some use against smallpox, the only proven way to afford protection is through pre-exposure vaccination. The vaccine used is made from a virus called vaccinia and is believed to provide immunity against smallpox for up to 10 years, with possible protection lasting up to 20 years following revaccination. Vaccination has an efficacy rate of around 95% and has even been shown to provide protection, or lesser infection, when given within four days immediately after exposure to the disease.
As with any vaccination policy, there are contraindications to the vaccine. The vaccine cannot be given to pregnant women, or to those with eczema or an impaired immune system. However, if a person has been exposed to the smallpox virus, risk of infection should be considered alongside contraindications.(9) It must also be remembered that at the time the vaccine was last used methods of testing were not as advanced as those in practice today, and much still needs to be learnt regarding the length of protection attained.
The smallpox vaccine is a live vaccine and is administered with a small two-pronged needle called a bifurcated needle into the upper arm or thigh. The needle is dipped into the vaccine and is then used to "poke" the skin. Following a normal reaction a papule will appear after three to four days. At day seven a pustule develops, which proceeds to crust over and appear as a brown scab at the vaccination site. The scab finally falls off after the third week, leaving a scar.(10)
Smallpox as a biochemical weapon
The use of smallpox as a biochemical weapon is not a new concept - historians believe it was first used by the British in North America around 1754. Infected blankets from smallpox patients were given to the Indians and were believed to account for a 50% death rate in some tribes.
With the discovery of a vaccine and eventual eradication of the disease the thought of re-emergence was not considered. It was during the 1980s that reports came from Russia claiming that the virus was being successfully used in the development of bombs and missiles.(11) The collapse of the Russian economy caused concern as some believed that the virus could have fallen into the wrong hands and potentially be used in an unlawful manner.
This fear has escalated since 11 September 2001 and the subsequent unrest in the Middle East. While experts continue to stress that the possibility of a bioterrorist attack using smallpox is very low, the Public Health Laboratory Service (PHLS) has put together interim guidelines providing advice to UK health professionals and managers in an effort to remain ahead of any possible attack.(12)
Ring vaccination and containment strategy
The UK has, at this time, chosen not to offer smallpox vaccination to the whole population on mass. The plan of action within the UK is that of ring vaccination and containment. This involves confining the infection and vaccinating those who fall within this ring. This differs from the American approach, which addresses the concern that ring vaccination would not work in big cities where contamination is most likely to occur. Instead, Americans are discussing mass vaccination of the entire population, beginning with health workers. According to the UK guidelines, vaccination would be offered only to key healthcare workers in the area of contamination, along with those involved with care of the infected and their families.(13)
It is recognised that a potential case will not be identified until it is confirmed by laboratory tests, after which the priority will be to identify the source and contain infection. The Department of Health, working alongside the PHLS, has advised all Primary Care Trusts (PCTs) to ensure that they have in place documentation outlining their reaction to such an emergency and response should such a major incident occur.(14) The aim of such ­guidelines reiterates how important it is for health workers to remain vigilant to the potential risk and have contingency plans in place. Early recognition of the disease is essential for containing and providing vaccination cover for those at risk.
While many have questioned the policy of ring vaccination, previous research highlights the dangers associated with a mass emergency vaccination. Due to the low risk of variola contamination through bioterrorist infection, mass vaccination of the whole population has not been recommended. The reasoning against mass pre-exposure vaccination is mainly due to the serious complications and even death that can potentially occur following vaccination if strict contraindications are not observed. Some sources have suggested that at least 15% of recipients could experience serious side-effects due to pre-existing contraindications.(15) Another concern with the smallpox vaccine is that of "contact vaccinia", a less serious form of smallpox. Experts suggest that those with existing skin disorders, such as eczema, could infect others who have not been vaccinated, with children under the age of four being at greater risk.(16)

Practice pointers
Much of the literature related to the potential release of the variola virus states that the risk is low; however, it is essential that health professionals are aware that a potential risk does exist. As well as having an understanding of smallpox, nurses should ensure that they are aware of any emergency and major incident policies within their PCT and know the role they would be expected to play in such a situation. With the growing use of the internet to disseminate information, educational material related to smallpox is essential viewing, with the best information coming from the Centers for Disease Control (CDC), which has produced free health professional training modules with graphics online.(10) One UK author in a smallpox briefing ­summarises the situation:(16)
"... if public confidence is maintained, there is good reason to believe that a terrorist release would indeed prove to have 'more bark than bite'. The real dangers come from official ­procrastination and irrational fear."


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  2. WHO. The history of vaccination. Available from URL: http://www.who. int/vaccines-diseases/history/history. shtml
  3. WHO. Frequently asked questions and answers on smallpox. Available from URL: diseases/smallpox/faqsmallpox.html
  4. CDC. Smallpox overview. Available from URL: smallpox/overview/disease-facts.asp
  5. TRAVAX. Information for health professionals. Available from URL:
  6. CDC. Smallpox information. Available from URL: smallpox/index.asp
  7. Breman J, Henderson DA. Diagnosis and management of smallpox. N Engl J Med 2002;346(17):1300-8.
  8. Public Health Laboratory Service. Smallpox: general information. Available from URL: topics_az/smallpox/gen_info.htm
  9. CDC. Smallpox vaccine contraindications. Available from URL: http://www.
  10. CDC. Online training material for health professionals - smallpox ­vaccination and adverse effects training module. Available from URL: http://
  11. Henderson DA, Inglesby TV, Bartlett JG, et al. Smallpox as a ­biological weapon: medical and public health management. Working Group on Civilian Biodefense. JAMA 1999;281(22):2127-37.
  12. PHLS. Smallpox - public health guidelines for action in the event of a deliberate release. Version 4. London:PHLS; 2002. Available from URL:
  13. Mayor S. Chief Medical Officer confirms key health workers will be vaccinated against smallpox [News]. BMJ2002;325:855.
  14. Department of Health. Emergency planning unit. Available from URL:
  15. ProMed. Posting correspondence October 2002. Available from URL:
  16. Neff JM, Lane JM, Fulginiti VA, Henderson DA. Contact vaccinia - transmission of vaccinia from smallpox vaccination. JAMA 2002;288(15):1901-5.
  17. Mortimer PP. The spectre of smallpox [Editorial]. Commun Dis Public Health 2002;5(2):92-3.

Further reading
Fenner F. Smallpox and its eradication. WHO Online Publication. Available from URL: