Smallpox is an acute infectious disease caused by the variola virus, which causes varying degrees of health threat to humans. The fatality rate is up to 30%. Deaths often occur within one or two weeks after symptom onset. So far, there is no effective treatment. The disease was first discovered in China and India in the 4th century, and more than 3.5 million people were killed in the world in the 16th century. By 1970, more than 15 million people were infected each year, with at least 2 million deaths worldwide. Therefore, the World Health Organization (WHO) planned to eradicate smallpox, and in 1980 officially announced that the smallpox virus eradicated completely on earth, which will not happen naturally, and recommended that all countries to stop vaccinia vaccination. Three attributes that lead to the success of the variola virus eradication program: construction of strategic disease surveillance system, rigorous isolation of possible cases and vaccination of all contacts. The variola virus has also become the first eradicated virus that causes human disease in nature. 

Smallpox Epidemiology in Taiwan

Since 1955, there has been no confirmed case reported in Taiwan. 

Smallpox Surveillance in Taiwan

  1. Taiwan National Infectious Disease Statistics System-Smallpox
  2. Fever screening at international airports and seaports.
  3. Self–reporting through the toll–free 1922 hotline or local public health authority.


A person may become infected by direct contact with smallpox patients or through inhaling the variola virus. The infected patient’s saliva, blood, tissue fluid, blister, scab, excrement and used contaminants are all infectious. 


Initial symptoms include fever, severe back pain and fatigue, followed by rash, headache, abdominal pain, and vomit. A rash starts as dots(days 2-3), which gradually form blisters (days 3-5), pustules (days 6-7), and then scabs (days 7-10). The rash develops on the face, arms and legs 2-3 days after symptom onset. It takes 3 weeks (21 - 28 days) to crust. Depressed, depigmented scars are left behind after scabs fall off.

Comparing to chickenpox, the rash in patients with smallpox is mainly distributed on the face and distal extremities, while the rash distribution in patients with chickenpox is centripetal, and the evolution is very regular. Centrifugal distribution of rash is the most important feature of smallpox. 


  1. Health Education: Educate citizens about smallpox transmission, vaccination, isolation and quarantine measures etc. Avoid contact with the oral or nasal secretions of patients and their contacts. Maintain good personal and environmental hygiene. Seek medical attention immediately when symptoms such as fever, rash, blisters or pustules develop.
  2. Case reporting and epidemiological investigation: Smallpox is classified as a Category I Notifiable Infectious Disease. Patients who meet the case definition of smallpox should be reported to the local health authority within 24 hours of identification.
  3. Vaccination: Vaccinia vaccination had been considered as the most effective way to prevent smallpox in the eradication program. At the end of the eradication program, the second and the third generation vaccines were developed. However, taking into consideration the limited vaccine stockpiles, the side effects and that the vaccine can still effectively ward off infection within 3 days following the exposure to smallpox virus, a universal vaccination program before the occurrence of an epidemic is not recommended. Currently, the vaccines are only reserved for certain groups, e.g., first responders and laboratory workers with a risk of exposure to smallpox. 


  1. What is smallpox?
    • Smallpox is a very serious illness caused by the variola virus.
  2. How is smallpox transmitted?
    • Smallpox is contagious. A person may be infected by direct contact with smallpox patients, or by inhalation of the variola virus. The infected patient’s saliva, blood, tissue fluid, blister, scab, excrement and used contaminants are infectious.
  3. What is the treatment for smallpox?
    • There is no proven treatment for smallpox, but some antiviral drugs may help treat it or prevent it from getting worse.
  4. What is the smallpox vaccine?
    • The first generation smallpox vaccines that were used for the eradication program is made from the vaccinia virus, which is another pox-type virus related to smallpox. The vaccine helps the body develop immunity to smallpox. The second generation smallpox vaccine is produced by cell culture with improved manufacturing process, maintaining consistency and minimizing the risk of contaminations. The third generation vaccines are made of attenuated strains, which have excellent safety profiles though they have proven field effectiveness against smallpox virus infection.
  5. What can be done to reduce the risk of infection of smallpox?
    • (1) Maintain good personal and environmental hygiene and avoid exposure to the oral or nasal secretions of patients and their contacts.
    • (2) Seek medical attention and notify the local health authority immediately if symptoms such as fever, rash, blisters or pustules develop.  

More Information

  1. WHO|Smallpox
  2. USA CDC|Smallpox



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發佈日期 2017/4/6