Smallpox
Topic Overview
What is smallpox?
Smallpox is a contagious infection caused by the variola virus. Smallpox can be deadly, so if an outbreak happens, it is vital to stay away from infected people. Get vaccinated if you have been around someone who has smallpox. And if you develop symptoms, seek medical care.
The telltale signs of smallpox are severe illness with a high fever, then a body rash. Symptoms appear about 12 days after the person is infected.
Before there was a vaccine, smallpox used to cause death all around the world. Thanks to widespread use of the vaccine, the last natural case of smallpox occurred in 1977. And in 1980 the World Health Organization (WHO) declared that the spread of smallpox was stopped and that the disease had been wiped out.
Because there is a slight risk of serious reactions and even death from the smallpox vaccine, routine smallpox immunization ended in Canada in 1972.
Smallpox virus is known to exist in labs at the Centers for Disease Control and Prevention (CDC) in the U.S. and at the Institute of Virus Preparations in Siberia, Russia. But it may also be in other labs. Some people worry that terrorists could release the virus and spread smallpox to many people.
What are the symptoms?
The first symptoms of smallpox include a high fever, fatigue, a headache, and a backache. It takes about 12 days for these symptoms to show. Then after 2 to 3 days of illness, a flat, red rash appears. It usually starts on the face and upper arms, and then it spreads all over your body. Over the next 2 to 3 weeks, the flat, red spots become firm and dome-shaped and fill with pus. Then they scab over. Scabs fall off 3 to 4 weeks after the rash first appears, and they leave pitted scars.
You may mistake a severe chicken pox rash for a smallpox rash at first. But different viruses cause these illnesses.
How is smallpox spread?
Smallpox is contagious. It can be passed from one person to another through coughing, sneezing, or breathing, or by contact with the scabs or the fluid from blisters. It can even spread from an infected person's personal items and bedding. Smallpox is easiest to spread during the first week of the rash. As scabs form, the person is less contagious. But a person can spread the virus from the time the rash first appears until all scabs have fallen off.
If a terrorist were to release a small amount of the virus into the air, it is possible that it could spread among a large number of people. The virus could survive and infect people for 6 to 24 hours, depending on the weather.1
People who get this disease must stay away from others to help prevent it from spreading. If there has been a smallpox outbreak and you think you might have been exposed, call your local health unit or 911. Do not go directly to a health facility, because you could pass the disease to other people.
How is smallpox diagnosed?
If a doctor suspected a case of smallpox, it would be considered a worldwide health emergency. Provincial and federal health officials would quickly take action. They would keep anyone who might have been exposed away from others. Then they would send lab samples to the National Microbiology Laboratory in Winnipeg. Experts there would test to see if the smallpox virus is present.
If a smallpox outbreak had been confirmed, a doctor could diagnose smallpox without a lab test. The doctor would look at the rash and ask about symptoms and possible exposure to the disease.
How is it treated?
There is no known cure for smallpox. Treatment includes drinking plenty of fluids and taking medicines to control pain and fever.
To prevent the spread of the virus, an infected person must be kept away from other people until he or she is no longer contagious.
Can smallpox infection be prevented?
People who have survived smallpox cannot get it again.
Also, there is a smallpox vaccine. It has vaccinia virus in it, which is like the smallpox virus but safer. If you get the shot before you've been exposed to smallpox, it will likely protect you for at least 3 to 5 years. And having a second shot later can protect you for at least 10 to 20 more years.2
The shot works even if you don't get it in advance. Most people who get the smallpox shot within 3 days after they've been exposed to the virus will have no symptoms or will have symptoms that aren't as severe. Getting a shot 4 to 7 days after exposure may also help.3
In the past, when a smallpox infection was diagnosed, infected people were kept away from others to prevent the spread of infection. Everyone who might have been exposed to the virus was then vaccinated. This practise, called ring vaccination, played a key role in wiping out smallpox. Many experts think it would be better to carry out ring vaccination before mass vaccination if there were a case today.
Because there are risks of a serious reaction from the vaccine, routine smallpox immunization doesn't occur. All children and most adults in Canada today have the chance of getting infected if they were exposed to the smallpox virus.
Since the September 2001 terrorist attacks on the U.S., more vaccine has been made. The Government of Canada has a stock of over 360,000 doses of the smallpox vaccine to help contain an outbreak. The government is also adding 10 million doses to its stock.4
 Go to top of page |  Go to next section | |
| Author: | Debby Golonka, MPH Carrie Henley | Last Updated: May 1, 2007 |
| Medical Review: | William M. Green, MD - Emergency Medicine Anne C. Poinier, MD - Internal Medicine W. David Colby IV, MSc, MD, FRCPC - Infectious Disease Christine Hahn, MD - Epidemiology | |
 | ||
