Poxviruses

Question 1

Poxviruses

Answer 1

• ds DNA enveloped
• replicate in cytoplasm

Question 2

Poxviruses that infect humans

Answer 2

•Orthopoxviruses

• Variola major (smallpox major)
• Variola minor (smallpox minor)
• Cowpox
• Vaccinia (hybrid of small pox and cowpox)
• Monkeypox

•Parapoxviruses

• Orf
• Pseudocowpox

•Molluscum contagiosum

Question 3

Poxviruses Structure

Answer 3

Question 4

Poxviruses Replication

Answer 4

• All events in cytoplasm
• Rapid adsorption to receptors
• Endocytosis (cytoplasmic vacuole).
• First uncoating is removal of outer membrane
• Second uncoating is partial removal of core membranes and proteins
• Leads to activation of viral DNA–dependent RNA polymerase
• Transcripts are translated into virus–coded enzymes which further degrade core proteins and release naked viral DNA

Question 5

Smallpox

Answer 5

• Orthopoxvirus genus of the Poxviridae family
• ds DNA enveloped
• smallpox
• Variola major (3-20% fatality)
• Variola minor (1% fatality)

Question 6

Smallpox Infection

Answer 6

• Infection by inhalation (respiratory tract)
• Virus first replicates in upper respiratory tract epithelial cells
• Spread to regional lymph nodes
• Viremia: target cells are skin, mucous membranes and internal organs

Question 7

Smallpox Symptoms

Answer 7

• Fever and malaise precede lesions
• Vesicles appear on face, arms and lower extremities (all at the same time)
• Considerable variation in outcome: mild to severe fulminant (genetics ?)

Question 8

Smallpox Complications

Answer 8

•keratitis, encephalitis, pneumonia, bacterial superinfections

Question 9

Smallpox Diagnosis

Answer 9

•Clinical picture, serology

Question 10

Smallpox Prevention

Answer 10

• Vaccinia virus (live vaccine), intradermal, must be 1 year of age
• Protection is not life long, revaccination at 10 year intervals.

Question 11

Smallpox Vaccine Adverse Reactions

Answer 11

• Generalized vaccinia: vesicles form over entire body
• Encephalitis (40% fatality)
• Progressive vaccinia: immunosuppressed patients, lesions enlarge (50% mortality rate)
• Pregnancy: death of fetus

Question 12

Smallpox Treatment

Answer 12

•Methisazone (Marboran), reduces severity, must be given early after infection

Question 13

Monkeypox

Answer 13

• Orthopoxvirus genus of the Poxviridae family
• ds DNA enveloped
• similar to smallpox but less severe
• Primary and secondary transmission possible
• Majority of the cases due to person-to-person transmission
• Animals may infect people through bites or people touching animal discharges and rubbing eyes or nose

Question 14

Orf

Answer 14

• Parapoxvirus of the Poxviridae family
• ds DNA enveloped
• natural infection in sheep and goats

–Human infection by contact, usually single lesion which spontaneously regresses

Question 15

Psedocowpox

Answer 15

• Parapoxvirus of the Poxviridae family
• Milker‘s nodules (cutaneous lesions similar to Orf, regress spontaneously)

Question 16

Molluscum Contagiosum

Answer 16

• Molluscipoxvirus genus of the Poxviridae family
• ds DNA enveloped
• Infection by contact (can be sexually transmitted)
• Cutaneous ”pearl– like“ lesions that regress spontaneously