Quick Facts about Smallpox
Information adapted from the CDC and Johns Hopkins Center for Civilian Biodefense Center.
Signs and symptoms
Post-exposure prophylaxis
Treatment
Signs and symptoms
- Smallpox is caused by the variola virus
- Incubation period is about 12 days (7 to 17 days)
- Mode of transmission
-
- Person to person by infected saliva droplets
- May be spread by contaminated clothing or bedding
- Most infectious during first week
- Remain infectious until scabs fall off
- Initial symptoms
-
- Fever, fatigue, head and back aches
-
- The absence of significant fever prodrome makes smallpox very unlikely.
- 50% vomiting, 10% diarrhea
- Characteristic rash within 2 -3 days
-
- Begins on face, proximal arms and legs
- Spreads to chest, distal extremities
-
- Most concentrated on the face and distal extremities
- At any one time, the rash is in the same stage of development on any one part of the body
- Stages of rash
- Flat, red rash followed in 2 days by
- Papules followed in 4 -5 days by
- Vesicles followed in 1 - 2 days by
- Pustules followed in 7 - 14 days by
- Crusts and scabs followed by
- Scabs falling off and scarring (2 - 3 weeks)
- Disease in previously vaccinated persons
-
- Vaccination ended in 1972
- Current level of immunity is unknown
- Persons are assumed to be susceptible
- Complications
-
- Secondary bacterial infections of the skin
- Keratitis and corneal ulceration
- Viral arthritis and osteomyelitis
- Bacterial pneumonia
- Orchitis
- Encephalitis
- Differential diagnosis
-
- Varicella (chickenpox)
-
- Rash begins on trunk, spreads to face and extremities
- Most lesions are concentrated on trunk or equally distributed between trunk and extremities
- At any one point in time, rash in different stages
- Diagnostic Tests
-
- Clinical presentation
- Virus culture
-
- Skin lesions, oropharynx, conjunctiva, urine
- Serological testing for antibody
-
- Pared samples 2 - 3 weeks apart
- Hemagluttination inhibition, compliment fixation, or gel precipitation
- DFA and IFA can be used to diagnose varicella-zoster virus
- Case fatality rate 30%
Post-exposure Prophylaxis
- The vaccine lessens severity or prevents illness
- Must be given within 4 days after exposure
- Vaccine
-
- Live vaccina virus
- Does not contain smallpox virus
Treatment
- No antiviral treatment available
- Antibiotics for secondary bacterial infections
- Supportive care (fluids, pain, fever)
- Mass vaccination for the general public is not recommended
-
- Risk currently outweighs benefits
- Sufficient vaccine not available
Search PIER® - Decision Support
ACP Members Only. Decision support for over 460 clinical topics.
Introducing ACP Clinical Shorts - Expert Education on Your Schedule
 |
|
10-minute videos give you answers to challenging clinical dilemmas seen in practice and are a terrific way to earn CME credit on-the-go. See more. |
ACP JournalWise: Reviews of the World's Top Medical Journals-FREE to ACP Members!
|
ACP JournalWise is mobile optimized with optional email alerts! Get access to reviews from over 120 of the world's top medical journals alerting you to the highest quality, most clinically relevant new articles based on your preferred areas of specialty. ACP Members register your FREE account now! |
