What is smallpox?

Smallpox is a serious and highly contagious disease caused by the variola virus. It was once a common virus, but has now been entirely removed from the world through vaccination. It killed millions of people worldwide before the World Health Organization (WHO) began an international immunisation campaign.

In 1980, the WHO announced that smallpox had been eradicated (removed) from the world. The last case in Australia happened in 1938. The last reported natural case worldwide was in Somalia in 1977.

After the disease was eradicated, all remaining stocks of the virus worldwide were destroyed. Two small amounts are still held in secure laboratories in the United States and Russia.

There is no risk of catching smallpox in Australia today. The only risk would be if the smallpox virus was used in an act of bioterrorism.

What are the symptoms of smallpox?

Symptoms of smallpox can develop 7 to 19 days of exposure to smallpox. In the first few days, symptoms include:

• fever over 40°C
• back and headaches
• chills
• body aches
• nausea and vomiting
• sore throat

About 3 days later a rash of fluid-filled blisters develops in the mouth and spreads over the body. These blisters crust over and form scabs. After about 3 weeks, the scabs fall off and leave scars.

What causes smallpox?

Smallpox is caused by the variola virus. This virus only infects humans and not animals. There are 2 types of variola:

• variola major — the more common and severe form of smallpox
• variola minor — a milder form of the virus with a lower death rate

Smallpox spreads from person to person through close contact. It can be transmitted by:

• inhaling droplets from a sick person that talks, coughs or sneezes
• touching surfaces contaminated by body fluids
• direct contact with fluids from smallpox blisters

There is also a risk that smallpox could be intentionally released into the environment as a bioterrorism agent.

How is smallpox diagnosed?

The chance of you getting smallpox is low. Your doctor will only suggest testing for the virus if your symptoms are the same as that of smallpox and you have been associated with:

• a specific threat
• suspected bioterrorism
• exposure to smallpox virus in a lab

If testing is needed, you will be referred to a specific high-security laboratory. There, samples will be taken of your:

• blister fluid
• smallpox scabs
• blood

Smallpox is a notifiable disease. The affected person and their contacts would be placed in isolation.

How is smallpox treated?

There is no cure for smallpox. In the past, it caused death in about 3 out of every 10 people who caught it.

If someone were to catch smallpox today, they would need fluids and pain-relieving medicines to manage symptoms. Antibiotics may be given if the blisters become infected with bacteria.

What are the complications of smallpox?

Smallpox can lead to severe complications. It may lead to death.

Complications of smallpox may include:

• scarring of the skin
• blindness
• pneumonia
• arthritis and joint deformities
• bone infections
• encephalitis

The smallpox vaccine can have side effects including:

• skin rash
• encephalitis
• death

Can smallpox be prevented?

The disease was removed from the world through vaccination. Since there is currently no risk of smallpox infection, the possible side effects from the vaccine outweigh the benefits of routinely vaccinating the general population.

If you receive the smallpox vaccine within 3 days of exposure to the virus, it can prevent you from getting sick.

Today's smallpox vaccine is made from the vaccinia virus. This is a related virus that cannot cause smallpox. Vaccinia virus replaced cowpox for vaccination because it has less severe side effects.

If there were ever an outbreak, how would it be managed?

The Australian Government Department of Health, Disability and Ageing has a smallpox emergency management plan. Australia has a supply of the smallpox vaccine to use in case of an outbreak.

The disease would be controlled by vaccinating and isolating anyone who came into contact with an infected person. This would include healthcare workers.

Is mpox the same as smallpox?

Mpox (monkeypox) is a viral illness that is related to smallpox. They are not the same virus. Mpox has similar symptoms to smallpox, but it is usually less severe and most people get better. It can potentially be a serious illness. It generally spreads through direct contact with blisters on an infected person.

Resources and support

• Department of Health, Disability and Ageing offers a smallpox emergency management plan.
• NSW Government offers a smallpox factsheet.
• WA Health offers information and resources about smallpox.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.

Other languages

You can read the guide for translating foreign immunisation terms to understand what you have been vaccinated against.