SMALLPOX VIRUS

Structure & Property	Transmission	Pathogenesis	Clinical findings	Laboratory diagnosis	Treatment	
Family: poxvirus

Genome: double strand DNA.

Size: 250-300nm

Brick-shaped enveloped particles.	Transmitted via respiratory aerosol or by direct contact with virus in the skin lesions or on fomites such as bedding.	Virus infects upper respiratory tract and local lymph nodes and then enters blood (primary viraemia). 

Internal organs are infected and virus reenters blood (secondary viraemia) and spreads to skin.

Immunity is lifelong.	Incubation period: 7-14 days
 
Sudden onset of prodromal syndromes: fever and malaise.

Rash appears suddenly: papular, vesicular, pustular, leaving pink scars in 2-3 weeks.

Now eradicated: was a severe febrile illness characterized by a profuse vesicular rash and a high mortality (20-50%).

Survivors were left with disfiguring facial scars.	Grow virus in cell culture or chick embryos.

Detect viral antigens in vesicular fluid by immunofluorescence.	Vaccinia vaccine: 
- live attenuated virus.
- prepared from vesicular lesions produced in skin or calves and sheep or grown in chick embryos.
- complications: mild reactions to fatal encephalitis, 1/800.
- methisazone used to treat complications.

Success of vaccine:
- no other reservoir
- virus produce only acute infections.
- vaccinia virus is an effective immunogen.