Poxvirus-smallpox 54

Import features
1.They are brick-shape,dsDNA viruses.
2.They can be seen by the light microscope because of their large size
3.They contain a DNA-de
penndent RNA polymerase,not found in other DNA viruses because the virus replicates in the cytoplasm.

1.Smallpox (variola or alastrim ) virus.
2.Vaccinia virus and cowpox virus belong to orthopoxvirus genus.Members of orthopoxvirus cross -react and elicit neutralizing antibodies . Therefore, vaccinia virus was used in imuunization against smallpox.

3. Molluscum contagiosum virus belongs to a different genus.

Smallpox

The last endemic case occured in 1977 and 1980 the WHO General Assembly certified that smallpox had been eradicated. The importance of smallpox should not be forgotten because:

1. It had a marked impact on the development of civilization.

2. It is the first disease to be controlled by immunization.

3. It is the first virus disease for which chemoprophylaxis (Methisazone) was available.

4. It is the first to be eradicated.

Prevention

The disease was eradicated by the global use of the live attenuated vaccinia virus caccine. The success of the vaccine in eradicating smallpox was dependent upon five critical factors:

1. Smaallpox has a single, stable serotype.
2. There is no animal reservoir, and humans are the only host.
3. The antibody response is prompt.
4. The disease is easily recognized clinically.
5. There is no carrier state or subclinical infection.