Smallpox

Smallpox is caused by the variola virus, an orthopoxvirus. It was once a feared and highly contagious disease found in every country around the world. The main feature of the illness was a rash of blisters or pustules on the skin, which eventually dried up and left permanent scars. Smallpox could be deadly if the virus attacked the circulatory system, bone marrow or respiratory system.

As recently as the 1960s, around 12 million people caught this disease each year and approximately two million died. The World Health Organization (WHO) mounted an aggressive worldwide immunization campaign, 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. Today only small stocks of the virus remain, in two designated laboratories.

Because smallpox has been eradicated, routine vaccination against it is no longer recommended and is not part of standard immunization schedules.

Symptoms of smallpox#

The smallpox virus incubated inside the body for between seven and 17 days, usually around 12 days. Symptoms included:

• Fever
• Headache
• Muscle aches and pain, particularly in the back
• A non-specific red rash on the face, body and limbs
• Feeling unwell, often severely enough to be confined to bed

The rash then developed into small blisters or pustules. The pustules split open, the scabs fell off, and scars were left behind. Death could result if the virus attacked the circulatory system, bone marrow or respiratory system.

Smallpox and the development of vaccination#

Smallpox played an important role in the history of vaccination. Since ancient times it was understood that surviving a smallpox infection gave lifelong immunity.

An 18th-century doctor, Edward Jenner, first discovered how to immunize people against smallpox. He noticed that milkmaids hardly ever caught the disease, and suspected that their earlier infection with the much milder disease known as cowpox had protected them. Jenner tested his theory by deliberately infecting a boy with cowpox taken from a milkmaid’s skin pustule. He then exposed the boy repeatedly to the smallpox virus, but the boy did not catch the disease. The word “vaccination” comes from this discovery, since “vacca” is Latin for cow.

Jenner and his contemporaries did not yet understand how vaccination worked, because bacteria and viruses had not been discovered. Using a similar technique, later researchers developed an effective smallpox vaccine based on a related virus called the vaccinia virus. Different formulations were used until the 1970s.

In 1967 the WHO launched a major campaign to eradicate smallpox, and within 12 years the disease was gone. The only remaining smallpox virus is held in two high-security WHO collaborating laboratories under strict international controls.

Smallpox has at times been assessed as a possible biological weapon that could be used in warfare or a terrorist attack. Although this is considered unlikely, planning for such an event has taken place, and limited supplies of smallpox vaccine are kept for essential medical personnel and contacts in case of an outbreak.

Immunization and HALO#

Immunization has saved more lives over the past century than almost any other medical advance, including antibiotics, and many infectious diseases have been brought under control by immunization programs. For example, cases of invasive Haemophilus influenzae type b (Hib) disease have declined by more than 90 per cent in many countries since the Hib vaccine was introduced. Immunization is one of the cheapest and most effective ways to prevent many infectious diseases.

The immunizations you may need depend on your health, age, lifestyle and occupation. Together these are referred to as HALO:

• Health: some health conditions can make you more vulnerable to vaccine-preventable diseases. For example, premature birth, asthma, diabetes, heart, lung, spleen or kidney conditions, Down syndrome and HIV may mean you benefit from additional or more frequent immunizations.
• Age: at different ages you need protection from different vaccine-preventable diseases. National immunization schedules set out recommended vaccines for babies, children, older people and others at increased risk. Many recommended vaccines are provided at no cost to particular groups, including some populations at higher risk.
• Lifestyle: lifestyle factors can affect your immunization needs. Traveling to certain destinations, planning a family, sexual activity, smoking, and playing contact sports that may expose you to someone else’s blood can all mean you benefit from additional or more frequent immunizations.
• Occupation: workers in aged care, childcare, healthcare, emergency services or sewerage repair and maintenance should discuss their immunization needs with their doctor. Some employers help with the cost of relevant vaccinations for their employees.

Key points#

• Smallpox is caused by the variola virus, an orthopoxvirus.
• Smallpox was eradicated by 1977, and only small stocks of the virus remain in two designated laboratories.
• Symptoms began with fever, headache and aches, followed by a rash that developed into blisters or pustules.
• Smallpox played an important role in the development of vaccination.
• Since ancient times it was understood that surviving smallpox conferred lifelong immunity.

Where to get help#