Smallpox

Smallpox is caused by the variola virus, an orthopoxvirus. Smallpox was once a feared and highly contagious viral disease that was found in all countries around the world. The main characteristic of the disease was a rash of blisters or pustules on the skin, which eventually dried up and left permanent scars.

Smallpox can be deadly if the virus attacks the circulatory system, bone marrow or respiratory system. As recently as the 1960s, around 12 million people caught this highly contagious disease and approximately two million people died every year.

The World Health Organization (WHO) mounted an aggressive worldwide campaign of immunisation and by 1977, the last naturally occurring case was detected in Somalia. Eradication was certified by a commission of scientists in 1979 and endorsed by the World Health Assembly the following year. Small stocks of smallpox virus remain in two designated international laboratories.

Vaccination against smallpox is not recommended in Australia and is not on the National Immunisation Program Schedule.

Symptoms of smallpox

The smallpox virus incubates inside the body for between seven and 17 days, usually for 12 days.

Symptoms include:

• Fever
• Headache
• Muscular aches and pain, particularly in the back
• A non-specific red rash on the face, body and limbs
• Feeling unwell and likely to be confined to bed
• The rash develops into small blisters or pustules. The pustules split, dry and scab, then the scabs fall off, leaving scars.

Death can result if the virus attacks the circulatory system, bone marrow or respiratory system.

Smallpox and vaccination

Smallpox has played an important role in the development of vaccination.

Since ancient times, it was common knowledge that an infection with smallpox conferred lifelong immunity. An 18^th century doctor, Edward Jenner, first discovered the key to immunising people against smallpox. He noticed that milkmaids hardly ever fell victim to the disease, and hypothesised that their prior infection with the relatively harmless disease known as ‘cowpox’ may have protected them.

Jenner tested his theory by deliberately infecting a boy with cowpox, harvested from the pus of a milkmaid’s skin pustule. Jenner then exposed the boy repeatedly to the smallpox virus, but the boy didn’t catch the disease.

The word ‘vaccination’ recognises Jenner’s discovery, since ‘vacca’ is Latin for cow. However, Jenner and his contemporaries still didn’t understand the underlying mechanisms of vaccination, as bacteria and viruses hadn’t yet been discovered.

Using a similar technique to that used by Jenner, researchers devised an effective smallpox vaccine based on a similar virus, called the vaccinia virus. Different formulations of this vaccine were used until the 1970s.

In 1967, the World Health Organisation mounted a major campaign to eradicate smallpox. Within 12 years, smallpox disease was eradicated.

Stores of smallpox and future vaccination

The only remaining smallpox viruses are contained in two WHO collaborating centres: the Centers for Disease Control, Atlanta, USA, and the Laboratory for Applied Microbiology at Koltsovo in the Novosibirsk region of the Russian Federation.

Smallpox has recently been assessed as a possible biological weapon that could be used in non-conventional warfare or in a terrorist attack. Although this is believed to be unlikely, planning for such an eventuality has commenced worldwide. In Australia, a small amount of smallpox vaccine is available for essential medical personnel and contacts in the case of an outbreak.

Immunisation programs

Immunisation has saved more lives this century than any other medical discovery, including antibiotics. Many infectious diseases have been contained by immunisation programs. For instance, cases of invasive haemophilus influenzae b (Hib disease) in Victoria have declined by more than 90 per cent since vaccination was introduced in 1993. Immunisation programs are one of the cheapest and most effective preventative measures against many infectious diseases.

Where to get help

• Your doctor

Things to remember

• Smallpox was once a feared viral disease, common in all countries around the world.
• An aggressive immunisation campaign eradicated smallpox by 1977.
• There is a small risk that smallpox could be released intentionally as a bioweapon and health departments around the world, including in Victoria, are planning for this possibility.

You might also be interested in:

• Infections - bacterial and viral.
  

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Last reviewed: September 2011

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<a href="http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Smallpox?open">Smallpox - Better Health Channel</a><br/>
Smallpox is caused by the variola virus, an orthopoxvirus. Smallpox was once a feared viral disease. An aggressive immunisation campaign eradicated smallpox by 1977, but small stocks of the virus remain in laboratories. Smallpox has recently been assessed as a possible biological weapon that could be used in non-conventional warfare or in a terrorist attack.

Content on this website is provided for education and information purposes only. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your qualified health professional. Content has been prepared for Victorian residence and wider Australian audiences, and was accurate at the time of publication. Readers should note that over time currency and completeness of the information may change. All users are urged to always seek advice from a qualified health care professional for diagnosis and answers to their medical questions.

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