Smallpox risk factors

Ways of contracting smallpox

Possible ways to become infected with smallpox include:

• Prolonged face-to-face contact with someone who has smallpox (usually someone who already has a smallpox rash).
  • This was how most people became infected with smallpox in the past. However, a person can be exposed to someone who has smallpox and not become infected.

• Direct contact with infected bodily fluids or an object such as bedding or clothing that has the virus on it.

• Exposure to an aerosol release of smallpox (the virus is put in the air).
  • On rare occasions in the past, smallpox was spread by virus carried in the air in enclosed places such as buildings, buses, and trains. The smallpox virus is not strong and is killed by sunlight and heat. In lab experiments, 90% of aerosolized smallpox virus dies within 24 hours; in the presence of sunlight, this percentage would be even greater.

Smallpox is not known to be spread by insects or animals.