Chapter 24: Pathogenic DNA Viruses

Question 1

Name two diseases caused by poxviruses and discuss their signs and symptoms.

Answer 1

• Smallpox and molluscum contagiosum are the main diseases of humans

Question 2

Discuss the signs and symptoms of smallpox

Answer 2

• Genus: Orthopoxvirus
  Also commonly known as variola existing in two forms:
• Variola major: Severe, mortality rate of 20% or higher
• Variola minor: less severe, less than 1% mortality rate
• The virus moves via the blood to the skin where it produces pox
• Scars result on the skin, especially on the face
• Variola infects internal organs, causing fever, malaise and delirium

Question 3

What are the two forms Smallpox/Variola exist in

Answer 3

Variola major: Severe mortality rate of 20% or higher
Variola minor: Less severe, less than 1% mortality rate

Question 4

Describe the signs and symptoms of Molluscum Contagiosum

Answer 4

• Caused by Molluscipoxvirus
• Skin disease characterized by oearlyl white to light pink, smooth, waxy papules (appear tumor like) typically on face, trunk and external genitalia

Question 5

Describe the progression of disease in poxvirus infections

Answer 5

All poxviruses produce lesions that progress through a series of stages
1) Macules - Flat reddened lesions
2) Papules - Raised sore lesions
3) Vesicles - Lesions fill with clear fluid
4) Pustules - Pus filled lesions; also known pocks or pox
5) Crust - Poxvirus pustules dry up
6) Scar - Penetrate the dermis

Question 6

Discuss the historical importance of poxviruses in immunization and their use in disease eradication.

Answer 6

**- Smallpox is the first human disease to be eradicated **
- Factor that enabled the eradication of smallpox :
- Inexpensve, stable and effective vaccine
- No animal reservoirs
- Obvious symptoms allow for quick diagnosis and quarantine
- Lack of asymptomatic cases
- Virus is only spread via close contact

Question 7

What factors enabled the eradication of smallpox

Answer 7

• Inexpensive, stable and effective vaccine
• No animal reserviors (Large factor)
• Obvious symptoms allow for quick diagnosis and quarantine
• Lack of asymptomatic cases
• Virus is only spread via close contact
• Stocks of the virus are maintained in laboratories in the U.S and Russia

Question 8

Describe Herpesviridae

Answer 8

• Viruses have enveloped polyhedral capsids and linear dsDNA
• Viruses attach to host cell’s receptor
• Viral envelope fuses with the cell membrane to facilitate entry into the cell
• Often latent; the virus enters sensory nerve cells and remains inactive inside infected cells. Reactivation causes recurrence of the disease manifestations

dsDNA

Question 9

Describe human herpesvirus 1

Answer 9

• Often result in slow-spreading skin lesions
  - Typically occur via casual contact in children
• Viral replication in epithelial cells results in painful, localized lesions on skin
• Infected cells fuse with neighboring uninfected cells to form syncytium which helps in cell to cell spread
• After primary infection viruses remain latent in ganglia

Question 10

Describe human herpesvirus 2

Answer 10

• Often result in slow-spreading skin lesions
• Infections occur between ages of 15 and 29 from sexual activity
• Viral replication in epithelial cells results in painful, localized lesions on skin
• Infected cells fuse with neighboring uninfected cells to form syncytium which helps in cell to cell spread
• After primary infection viruses remain latent in ganglia

Question 11

Define syncytium

Answer 11

Infected cells fuse with neighboring uninfected cells to form a syncytium, which helps in cell to cell spread.

Question 12

Describe the diseases caused by human herpesvirus 1 and 2, including their signs, symptoms, and prevention.

Answer 12

• Characteristic fever blisters or cold sores:
• HHV-1: Oral Herpes; above the waist”
  -HHV-2: Genital herpes, “below the waist”
• Occular: conjunctivitis, blindness
• Whitlow: inflamed blister on finger
• Neonatal herpes: HHV-2; from mom to baby during birth; severe

Question 13

Describe oral herpes

Answer 13

• Infection of human Herpesviruses 1 and 2
• Mostly caused by HHV1
• Characterized by fever blisters or cold sores; painful, itchy skin lesions on the lips that can last 7 to 10 days
• Initial infections may also be accompanied by flulike signs and symptoms including malais, fever and muscule pain
• “Above the waist”

Question 14

Describe genital herpes

Answer 14

• Infections of human Herpesvirus 1 and 2
• Mostly caused by HHV2
• Painful lesions on the genitalia because the virions are typically sexually
• Can also cause oral lesions when it infects the mouth
• “Below the waist”

Question 15

Describe ocular herpes

Answer 15

• Caused by latent herpesviruses
• Symptoms and signs usually occur in only one eye including:
• A gritty feeling
• Conjuctivitis
• Pain
• Sensitivity to light

Question 16

Describe whitlow

Answer 16

• Inflamed blister on finger, usually only one finger
• Either HHV-1 HHV-2 enters a cut or break in the skin of a finger
• Hazard for:
• Childeren who suck their thumbs
• Health care workers in the fields of obstetrics, respiratory care, gynecology, and dentistry who come into contact with lesions

Question 17

Describe neonatal herpes

Answer 17

• A fetus can be infected in utero if the virus crosses the placetal barrier, but is more likely for a baby to be infected at brith through contact with lesions in the mother’s reproductive tract
• Mothers with oral lesions can infect their babies if they kiss them on the mouth
• To protect the baby, deliery should be by cesarean section if genital lesion are present at the time of birth

Question 18

List conditions that may reactivate latent herpesviruses.

Answer 18

• Latent herpsviruses: may remain inactive inside infected cells, often for years.
• May reactivate as a result of aging, chemotherapy, immunosuppresion, or physical and emotional stress, causing a recurrence of the manifestations of the diseases

Question 19

Describe the treatment for Herpesviruses 1 and 2

Answer 19

Nucleoside analogs; Valaciclovir will limit the duration of the lesions and reduce viral shedding but it doesn’t cure the disease or eliminate latent virus

Question 20

Describe chickenpox

Answer 20

Also known as Varicella -

Question 21

Compare and contrast chickenpox in children to shingles in adults

Answer 21

• Human herpevirus 3 commonly varicella-zoster virus (VZV)

Question 22

Describe the diseases associated with Epstein-Barr virus

Question 23

Describe genital herpes