Busm Id- Lec 19A Poxviruses

Front 1

Lecture 19A
Learning Objective 1:

Describe the basic structural features of poxviruses.

Back 1

Virion characteristics
1. Brick or ovoid-shaped

2. Complex structure= not icosahedral or helical

3. Envelope is not required for infectivity- and is also made of virus proteins instead of host cell membrane= makes them tough!

4. ds DNA genome: 130-375 kbp encodes 150-300 proteins

Front 2

Lecture 19A
Learning Objective 2:

Explain the basic steps in the poxvirus replication cycle including how the virus enters the cell, where replication and assembly occurs and wheter host or viral polymerases are used for transcription and genome replication, and how progeny are released.

Back 2

1. Core is released into
cytoplasm

2. Early transcription by viral
polymerase

3. Release of DNA from core

4. DNA replication by viral
polymerase

5. Late transcription by viral
polymerase

6. Assembly and release by
budding or lysis

Front 3

Lecture 19A
Learning Objective 3:

Explain how variola virus, molluscum contagiosum virus, and orf virus are transmitted.

Back 3

Variola virus:
Direct contact with an active case (symptoms present).
Via respiratory droplets, direct contact with skin lesion or a contaminated fomite
Human disease only.
Not contagious during asymptomatic incubation period.

Molluscum contagiosum:
Also human only.
Virus is limited to epidermis (ie not systemic) so it's spread by direct contact with the skin lesion or a fomite.

Orf virus:
Disease of sheep and goats.
Transmitted to humans via direct contact with lesion on animal ususally at the site of an abrasion (on the human).

Front 4

Lecture 19A
Learning Objective 4:

Describe the major clinical features of smallpox, monkeypox, molluscum contagiosum, and orf.

Back 4

Smallpox: 30% mortality. Day 8 fever, day 12-14 high fever and severe pains, day 16-18 rash starts on face, spreads to whole body, starts as vesicular, then becomes pustular (lasting 2 weeks) then becomes crusty.

Monkeypox: Similar to smallpox, 15% mortality.

Molluscum: Small papular painless tumors of the skin (anywhere except palms and soles) or mucous membranes, lesions have a cup shaped crater with a white core, and are found in clusters of 5-20. Limited to epidermis= not systemic. may take months to years to go away.

Orf:
usually just one or two self contained lesions at the site of an abrasion.

Front 5

Lecture 19A
Learning Objective 5:

Describe whether or not recovery from smallpox is associated with lifelong immunity.

Back 5

Yes, if you do not die from smallpox you are immune for life.

Front 6

Lecture 19A
Learning Objective 6:

Describe the vaccine available for smallpox and explain how it protects against it.

Back 6

Vaccina virus is isolated from calf lymph. it's administerd by scratching it into the arm with a needle. If the vaccine "takes" you develop a pustular lesion at the vaccine site 6-10 days after. Immune response to the Vaccina virus provides cross immunity to smallpox virus.

Front 7

Lecture 19A
Learning Objective 7:

Describe the possible complications associated with the smallpox vaccine and the conditions in which giving it is contraindicated.

Back 7

Complications: accidental infection of other sites (eye), generalized vaccina= lesions all over body, or vaccinia necrosum= body dosnt mount a good enough immune responce and the virus becomes systemic leading to eczema vaccinatum, can be fatal. It can also cause cardiac events.

Contraindicated in immunocompromized people and pregnant women (?).

Front 8

Lecture 19A
Learning Objective 8:

Describe how to decontaminate items contaminated with poxviruses.

Back 8

Disinfectants for hard surfaces, hot water and bleach for clothing/linens.