Smallpox
An eradicated but historically devastating disease caused by variola virus, retained as a preparedness concern because of laboratory and deliberate-release risks.
What causes Smallpox?
Smallpox is caused by variola virus. Historically it spread through prolonged face-to-face contact, respiratory droplets, direct contact with lesions or scabs, and contaminated bedding or clothing.
Symptoms and what to notice
Sudden high fever, severe headache, exhaustion, back pain, and sometimes vomiting, followed by a deep, firm rash that progresses in the same stage on the face and limbs, including palms and soles.
How long can it last?
Incubation is usually 7 to 17 days. Illness unfolds over several weeks as lesions become pustules and scabs. A person is contagious from rash onset until the last scab falls off.
How serious is Smallpox?
Variola major killed about 3 in 10 infected people historically and could cause blindness, severe scarring, encephalitis, or pregnancy loss. Any suspected case is an international public-health emergency.
Treatment and management
No naturally occurring cases exist. A suspected case requires immediate isolation and public-health response. Tecovirimat and brincidofovir are FDA-approved for smallpox; cidofovir and other countermeasures may be considered only under specialist federal guidance. Supportive intensive care is essential.
Vaccine: who and when?
Routine public vaccination is not recommended because smallpox is eradicated. Licensed U.S. stockpile vaccines are JYNNEOS and ACAM2000; APSV is also stockpiled under investigational access. JYNNEOS or ACAM2000 is used for selected occupational risk and emergency response, with product choice based on contraindications and exposure.
Cost note: Patient cost varies by product, provider, insurance, location, and eligibility. Many recommended vaccines are covered in network without cost sharing, and qualifying children may use the Vaccines for Children program.
Trusted source
Patient cost varies by insurance, provider, location, and eligibility. Coverage and public-health access differ, so listed prices are examples rather than guaranteed patient prices. This page is for general education and does not replace individualized medical advice, diagnosis, vaccination assessment, or treatment.
Smallpox: Symptoms, Causes, Treatment, Prevention, and Vaccine Information
Smallpox is the only human infectious disease eradicated worldwide. The last naturally occurring case was in 1977 and eradication was declared in 1980. Variola virus remains a preparedness concern, so laboratories, governments, and healthcare systems maintain diagnostic, vaccine, antiviral, and response plans.
Important: This page is for general education. It does not replace diagnosis, treatment, vaccination advice, or emergency care from a qualified healthcare professional.
Quick Facts
| Topic | Current information |
|---|---|
| Cause | Smallpox is caused by variola virus. Historically it spread through prolonged face-to-face contact, respiratory droplets, direct contact with lesions or scabs, and contaminated bedding or clothing. |
| Main symptoms | Sudden high fever, severe headache, exhaustion, back pain, and sometimes vomiting, followed by a deep, firm rash that progresses in the same stage on the face and limbs, including palms and soles. |
| Typical course | Incubation is usually 7 to 17 days. Illness unfolds over several weeks as lesions become pustules and scabs. A person is contagious from rash onset until the last scab falls off. |
| Treatment | No naturally occurring cases exist. A suspected case requires immediate isolation and public-health response. Tecovirimat and brincidofovir are FDA-approved for smallpox; cidofovir and other countermeasures may be considered only under specialist federal guidance. Supportive intensive care is essential. |
| Vaccine status | Routine public vaccination is not recommended because smallpox is eradicated. Licensed U.S. stockpile vaccines are JYNNEOS and ACAM2000; APSV is also stockpiled under investigational access. JYNNEOS or ACAM2000 is used for selected occupational risk and emergency response, with product choice based on contraindications and exposure. |
History and Public-Health Importance
For centuries smallpox reshaped populations and killed hundreds of millions. Variolation preceded Jenner’s 1796 cowpox vaccination. A global campaign combining vaccination and surveillance interrupted transmission. Eradication ended routine U.S. vaccination, but select laboratory personnel remain vaccinated and national stockpiles support emergency response.
What Causes Smallpox?
Smallpox is caused by variola virus. Historically it spread through prolonged face-to-face contact, respiratory droplets, direct contact with lesions or scabs, and contaminated bedding or clothing.
Historically, sustained face-to-face contact was the main route, with contaminated linens and lesion material also important. Patients became contagious at rash onset rather than during incubation. Infection-control response would use airborne and contact precautions, dedicated facilities, and rapid ring vaccination of contacts.
Symptoms and Typical Course
Sudden high fever, severe headache, exhaustion, back pain, and sometimes vomiting, followed by a deep, firm rash that progresses in the same stage on the face and limbs, including palms and soles.
After an asymptomatic incubation, high fever and systemic illness appear abruptly. A centrifugal rash begins in the mouth and on the face, then spreads to arms and legs. Lesions are deep-seated and progress together from macules to papules, vesicles, pustules, and scabs. This pattern differs from chickenpox, whose lesions appear in crops.
Complications and Who Is at Higher Risk
Variola major killed about 3 in 10 infected people historically and could cause blindness, severe scarring, encephalitis, or pregnancy loss. Any suspected case is an international public-health emergency.
Death, severe scarring, blindness from corneal disease, arthritis, bone infection, encephalitis, pneumonia, and pregnancy loss occurred. Vaccine adverse-event risk is also important: replicating ACAM2000 can cause myocarditis, progressive vaccinia, eczema vaccinatum, or transmission to contacts in susceptible recipients.
How It Is Diagnosed
Any credible suspicion requires immediate contact with health authorities and CDC before routine specimen handling. Specialized PCR at public-health laboratories confirms variola. Ordinary laboratories should not independently culture or manipulate suspected specimens.
Treatment and Recovery
No naturally occurring cases exist. A suspected case requires immediate isolation and public-health response. Tecovirimat and brincidofovir are FDA-approved for smallpox; cidofovir and other countermeasures may be considered only under specialist federal guidance. Supportive intensive care is essential.
Tecovirimat and brincidofovir are FDA-approved for smallpox based largely on animal-rule evidence because human efficacy trials are impossible. Cidofovir and vaccinia immune globulin may have roles under federal guidance. Treatment and vaccination decisions would be coordinated through CDC and emergency-response systems.
Vaccine Information
Routine public vaccination is not recommended because smallpox is eradicated. Licensed U.S. stockpile vaccines are JYNNEOS and ACAM2000; APSV is also stockpiled under investigational access. JYNNEOS or ACAM2000 is used for selected occupational risk and emergency response, with product choice based on contraindications and exposure.
JYNNEOS uses nonreplicating modified vaccinia and has fewer contraindications. ACAM2000 uses replicating vaccinia delivered by scarification and requires careful screening and site care. Routine vaccination is not justified for the public while disease remains eradicated. Selected orthopoxvirus laboratory workers and emergency contacts follow ACIP or incident-specific schedules.
Prevention
Maintain secure laboratory practices, occupational vaccination for qualifying workers, surveillance, rapid isolation, contact tracing, and strategic stockpiles. The public does not need routine smallpox vaccination.
When to Seek Medical Care
A fever followed by a firm, synchronous pustular rash after a credible laboratory or public-health alert requires emergency contact with health authorities. Do not enter a clinic unannounced; call emergency services and describe the concern.
Frequently Asked Questions
Does smallpox still circulate naturally?
No. Global eradication was declared in 1980.
Should the public get vaccinated now?
No. Routine public vaccination is not recommended because disease is eradicated and vaccines have risks.
Which vaccines are licensed?
JYNNEOS and ACAM2000 are licensed U.S. smallpox vaccines and are held for occupational and emergency use.
Is smallpox the same as chickenpox?
No. They are caused by different viruses and have different rash patterns and severity.
Key Takeaway
Smallpox is eradicated, so routine vaccination is unnecessary. Preparedness rests on secure laboratories, specialist vaccination, rapid recognition, and coordinated public-health response.
Medical, treatment, and vaccine information was reviewed against official U.S. public-health guidance available through September 2026.