Communicable disease factsheets

Smallpox

Smallpox is a serious infectious disease, which was once frequent, particularly in socially disadvantaged countries. Smallpox infection was eradicated from Australia many years ago, and WHO announced worldwide eradication in 1979.

• Smallpox is a serious infectious disease, which was once frequent, particularly in socially disadvantaged countries.
• Smallpox infection was eradicated from Australia many years ago, and WHO announced worldwide eradication in 1979. The last case of endemic (naturally transmitted) smallpox occurred in Somalia in 1977.
• The smallpox virus is kept only at two high security laboratories overseas in the USA and Russia. It is very unlikely it has been removed from these laboratories.
• Smallpox vaccine is no longer made or registered for use in Australia. Commercial production of smallpox vaccine in the world ceased more than 20 years ago. However, Australian health officials have had discussions with international organisations to secure access to adequate quantities of vaccine in the unlikely event of a smallpox incident.
• Vaccination against smallpox is not recommended to prevent the disease in the general public and, therefore, is not available in Australia and in most countries of the world. This is because:
  • The disease was wiped out globally in the late 1970s
  • The risk of any incident leading to exposure to smallpox is low
  • The smallpox vaccine is not without complications and it should not be given if the risk from the vaccine is greater than the risk of exposure.
  • No one is at risk of contracting naturally occurring smallpox in Australia. The risk of a terrorist incident is low.
• In the unlikely event of people in Australia becoming exposed to smallpox, the vaccine can lessen the severity of or even prevent illness if given within four days of exposure.
• Smallpox is caused by variola virus. The incubation period is about 12 days (range: 7 to 17 days) following exposure. Initial symptoms include high fever, fatigue, and head and back aches. A characteristic rash, most prominent on the face, arms, and legs, follows in 2-3 days. The rash starts with flat red lesions that evolve at the same rate. Lesions become pus-filled and begin to crust early in the second week. Scabs develop and then separate and fall off after about 3-4 weeks. The majority of patients with smallpox recover, but death occurs in up to 30% of cases.
• Smallpox is spread from one person to another by infected saliva droplets that expose a susceptible person having face-to-face contact with the ill person. Persons with smallpox are not infectious during the incubation period but are most infectious during the first week of severe illness, because that is when the largest amount of virus is present in saliva. However, smallpox is not as contagious as measles or chicken-pox; people with symptoms would be confined to bed, and would not easily be able to infect others during the most infectious period. However, some risk of transmission lasts until all scabs have fallen off.
• Routine vaccination against smallpox was introduced in Australia around 1917 because of an epidemic in NSW. However, by the 1950s, in most parts of the country, vaccination was only mandatory for those travelling overseas or for medical students and nurses and others at potentially greater risk of exposure. Vaccination was no longer required for any Australians following global eradication of smallpox in the 1970s.
• The level of protection for persons vaccinated in the past is uncertain. Such persons are assumed to be susceptible. However, if they are subsequently exposed to smallpox, there is reason to believe that any illness will be short-lived and that they will be less likely to spread the infection to others.
• In the unlikely event that smallpox were introduced into Australia, it would be rapidly controlled because:
  • Australia has good surveillance for communicable diseases;
  • smallpox would not be expected to spread rapidly in a country like Australia, where living conditions are good;
  • people becoming ill would be treated in specialist facilities to prevent them spreading the infection to others;
  • there has been research on new treatments for smallpox over the last 20 years which could be available in the unlikely event of a smallpox incident; and
  • contacts would be vaccinated and kept under enhanced surveillance.