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SMALLPOX PATHOGEN: • Smallpox is caused by the variola virus, a large, non-enveloped, DNA virus belonging to the

Poxviridae family RESERVOIR(S): • Humans are the only host and the only reservoir for the virus. TRANSMISSION: • Smallpox is primarily transmitted by the respiratory route via inhalation of small, aerosolized

respiratory droplets. • It may also be transmitted by contaminated fomites, such as bedding used by a person with

smallpox, and by direct contact with the lesions of the rash. DISEASE: • There are two types of the disease: variola minor, which has a mortality rate of less than

1%, and variola major, which has a mortality rate of 30%. • The virus is inhaled, travels to the lower respiratory tract, and infects regional lymph nodes. It

then enters the blood and infects many organs in the body, where it replicates. Replication of the virus in the skin presents as a vesicular rash. Each of the vesicles or lesions in the skin contains live virus, and the rash is therefore infectious. When these lesions heal, they leave a pitted scar, called a pock. Those who survive are often disfigured or blinded by the disease.

• The first symptoms of the disease include a high fever, headache, and malaise and are

followed 2-3 days later by the rash.

• Death occurs due to toxemia (the result of virus in the blood) and hemorrhage.

TREATMENT: • Antibiotics are not effective, because the disease is caused by a virus. Supportive therapy

is the only treatment. VACCINE: • Smallpox was eradicated worldwide in 1980 due to an extensive vaccination program.

• The vaccine contains live vaccinia virus, a close relative to the variola virus, which provides

protection against smallpox and which cannot cause the disease. • Because there are no humans who have smallpox today, the general public is no longer

vaccinated for smallpox.