Report Immediately by Phone
Potential Bioterrorism Agent: Category A
Hospital: Report immediately by phone
Lab: Report immediately by phone, send specimens for testing to State Hygienic Laboratory
Physician: Report immediately by phone
Local Public Health Agency (LPHA): Immediate follow-up required. Iowa Department of Public Health will lead the follow-up investigation.
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
After Hours: Iowa State Patrol Office at (515) 323-4360
Smallpox is caused by the variola virus that emerged in human populations thousands of years ago. Except for laboratory stockpiles, the variola virus has been eradicated in the world.
B. Clinical Description
Symptoms: There is a clinical spectrum of disease with smallpox. Smallpox occurs in two clinical forms: variola major and variola minor. Variola major causes a more severe form of smallpox, with a more extensive rash and higher fever. Variola major has four distinct syndromes: ordinary (the most frequent type, accounting for 90% or more of cases); modified (mild and occurring in previously vaccinated persons); flat; and hemorrhagic (rare and very severe). Historically, variola major has an overall fatality rate of about 30%; however, flat and hemorrhagic smallpox usually are fatal. Variola minor is a less common presentation of smallpox, and a much less severe disease, with death rates historically of 1% or less.
Onset: The first symptoms of smallpox include fever, malaise, head and body aches, and sometimes vomiting. The fever is usually high, in the range of 101o to 104o Fahrenheit. At this time, people are usually too sick to carry on their normal activities. This is called the prodrome phase and may last for 2 - 4 days.
A rash emerges first as small red spots on the tongue and in the mouth. These spots develop into sores that break open and spread large amounts of the virus into the mouth and throat. This is when the person is most contagious. Around the time the sores in the mouth break 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 the rash spreads to all parts of the body within 24 hours. As the rash appears, the fever usually falls and the person may start to feel better. By the third day of the rash, the lesions become raised bumps. By the fourth day, the bumps fill with a thick, opaque fluid and often have a depression in the center that looks like a bellybutton. (This is a major distinguishing characteristic of smallpox.) Fever often will rise again at this time and remain high until scabs form. The bumps become pustules—sharply raised, usually round and firm to the touch as if there’s a small round object under the skin. People often say the bumps feel like BB pellets embedded in the skin. 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. The scabs begin to fall off, leaving marks on the skin that eventually becomes pitted scars. Most scabs will have fallen off three weeks after the rash appears. The person is contagious to others until all of the scabs have fallen off.
Complications: arthritis was a common complication, all others are rare. They may include secondary bacterial infection of skin lesions, sepsis, corneal ulceration and keratits, pulmonary edema, bronchopneumonia due to secondary bacterial infection, diarrhea, extensive viral infection of the intestinal mucous membrane, orchitis, hematuria, and encephalitis.
Common reservoirs: Humans are the only natural reservoir for smallpox. However, in the aftermath of the events of September and October, 2001, there is heightened concern that the variola virus might be used as an agent of bioterrorism.
D. Modes of Transmission
Spread: Generally, direct and fairly prolonged face-to-face contact is required to spread smallpox from person to person.
Airborne: On rare occasions, smallpox has been spread by virus carried in the air in enclosed settings such as buildings, buses, and trains.
Person-to-person: Smallpox also can be spread through direct contact with infected bodily fluids, scabs of lesions, or contaminated objects such as bedding or clothing.
E. Incubation period
This incubation period averages about 12 - 14 days, but can range from 7 - 17 days.
F. Period of Communicability or Infectious Period
At about four days into illness a rash emerges first on the tongue and mouth and spreads to the rest of the body. A person is contagious from the time the rash appears until all the scabs have fallen off. This is approximately 3 weeks.
Smallpox outbreaks had occurred from time to time for thousands of years, but the disease is now eradicated after a successful worldwide vaccination program. The last case of smallpox in the United States was in 1949. The last naturally occurring case in the world was in Somalia in 1977. After the disease was eradicated from the world, routine vaccination against smallpox among the general public was stopped because it was no longer necessary for prevention. Vaccination of healthcare response teams and the military against smallpox has been reinstated due to the potential use of smallpox as a biological weapon.
Except for laboratory stockpiles, the variola virus has been eliminated.
H. Bioterrorism Potential
Category A: There are concerns that the smallpox virus could be used for bioterrorism.
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Smallpox can be found at:
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
CDC Website. Smallpox www.bt.cdc.gov/agent/smallpox/index.asp
Heymann, D., L., ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC: American Public Health Association, 2015.
CDC. Vaccines & Preventable Diseases: www.cdc.gov/vaccines/vpd-vac/default.htm
Iowa Dept. of Public Health. Smallpox website: www.idph.state.ia.us/CADE/DiseaseIndex.aspx?disease=Smallpox