What to know
- A person with smallpox goes through several stages as the disease progresses. Each stage has its own signs and symptoms.
- It can take 7 to 19 days after being infected before a person shows symptoms of smallpox.
- People with smallpox will develop a rash, which progresses to pustules and then scabs.
- A person with smallpox is no longer contagious after all scabs have fallen off.
Incubation period
This stage can last anywhere from 7 to 19 days (although the average length is 10 to 14 days).
Contagious? No
The incubation period is the length of time the virus is in a person's body before they look or feel sick. During this period, a person usually has no symptoms and may feel fine.
Initial symptoms
This stage lasts anywhere from 2 to 4 days.
Contagious? Sometimes. Smallpox may be contagious during this phase but is most contagious during the next 2 stages (early rash and pustular rash and scabs).
The first symptoms include:
- High fever
- Head and body aches
- Sometimes vomiting
At this time, people are usually too sick to carry on their normal activities
Early rash
This stage lasts about 4 days.
Contagious? Yes. At this time, the person is most contagious.
A rash starts as small red spots on the tongue and in the mouth. These spots change into sores that break open and spread large amounts of the virus into the mouth and throat. The person continues to have a fever.
Once the sores in the mouth start breaking down, a rash appears on the skin, starting on the face and spreading to the arms and legs, and then to the hands and feet. Usually, it spreads to all parts of the body within 24 hours. As this rash appears, the fever begins to decline, and the person may start to feel better.
By the fourth day, the skin sores fill with a thick, opaque fluid and often have a dent in the center.
Once the skin sores fill with fluid, the fever may rise again and remain high until scabs form over the bumps.
Pustular rash and scabs
This stage lasts about 10 days.
Contagious? Yes
The sores become pustules (sharply raised, usually round and firm to the touch, like peas under the skin).
After about 5 days, the pustules begin to form a crust and then scab.
By the end of the second week after the rash appears, most of the sores have scabbed over.