Chapter 24- Pathogenic DNA Viruses

Question 1

What are some general characteristics of the Poxviridae family?

Answer 1

dsDNA virus

Have complex capsids and envelopes

Second largest virus

Infects many mammals, however, most animal poxviruses are species specific

Infection ocurs primarily through the inhalation of viruses- need close contact

Diseases- smallpox and molluscum contagiosum

Some diseases of animals can be transmitted to humans

Question 2

What are the stages of the formation of a lesion of a poxvirus infection?

Answer 2

1. Macule- reddened skin
2. Papule- rising of reddened area
3. Vesicle- fills with fluid
4. Pustule- fills with pus
5. Forms a crust
6. Scar forms

Question 3

What are some general characteristics of smallpox?

Answer 3

Genus Orthopoxvirus

Commonly known as variola- has 2 forms

Variola major- severe, mortality rate greater than 20%

Variola minor- less severe, less than 1% mortality rate

Virus moves via the blood to the skin, where it produces pox- scars result on the skin, esp. the face

Smallpox is the first human disease to be eradicated?

Question 4

How could smallpox be eradicated?

Answer 4

Inexpensive, stable, and effective vaccine

No animal reservoirs

Obvious symptoms allow for quick diagnosis and quarantine

Lack of asymptomatic cases

Virus spreads only by close contact

Question 5

What are characteristics of the disease Molluscum Contagiosum?

Answer 5

Caused by Molluscipoxvirus

Spread by contact among infected individuals- children, sexually active individuals, AIDS patients

Skin disease chracterized by pearly white to light pink, smooth, waxy papules (appear tumor like), typically on face, trunk, and external genitalia

People with normal immuntiy heal without treatment

Question 6

What are some characteristics of Herpesviridae?

Answer 6

Viruses have enveloped polyhedral capsids and linear dsDNA

Viruses attach to a host cell’s receptor and viral envelope fuses with the cell membrane to facilitate entry into the cell

Exits via exocytosis or lysis

Most prevalent DNA viruses

Often latent- virus enters sensory nerve cells and remains inactivated in infected cells, reactivation causes recurrence of disease manifestation

Assigned HHV and a number in order of discovery

Question 7

What are characteristics of the infections caused by HHV1 and HHV2?

Answer 7

Often results in slow-spreading skin lesions

Formerly known as herpes simplex virus or HSV

Caused by close contact

Result in painful, localized lesions on skin

Infected cells fuse with neighboring uninfected cells to form synctium which helps in cell to cell spread

Question 8

What are the specific diseases caused by HHV1 and HHV2 and their characteristics?

Answer 8

Characteristic fever blisters or cold sores

Oral herpes (HHV-1)

Genital herpes (HHV-2)

Ocular herpes

Whitlow- virus enters if there is a cut or break in skin

Neonatal herpes- transmitted from mother to child

Diagnosis- characteristic lesions, infected tissue reveal syncytia, immunoassays

Treatment- valaciclovir and other nucleoside analogs

Question 9

What are the types of infections caused by HHV3?

Answer 9

Varicella-Zoster Virus

2 Diseases

Varicella- often called chicken pox, affects children usually

Herpes zoster- also called shingles, usually occurs in adults

Question 10

What are the characteristics of chicken pox and shingles?

Answer 10

Chicken pox- highly contagious, enters through respiratory tract of eyes, travels via the blood from infection site to rest of body, characteristics skin lesions (dew drops on rose petals) appear 2-3 weeks after infection

Disease is usually more mild in child and more severe in adults

Shingles- caused by latent virus reactivation producing a rash, characteristic localization of shingle lesions along a band of skin called a dermatome

Question 11

How is an HHV3 virus infection diagnosed, treated, and prevented?

Answer 11

Diagnosis- chicken pox is diagnosed by characteristic skin lesions, shingles more difficult to diagnose

Treatment- chicken pox is self limiting, shingles is the management of symptoms

Prevention- difficult because virus is shed before obvious signs appear, vaccination

Question 12

What are some general characteristics of HHV4?

Answer 12

Also referred to Epstein-Barr Virus, EBV

Can cause a number of different diseases

Transmission occurs via saliva

EBV enters the blood and invades B lymphocytes

Large lobed B lymphocytes with atypiacl nuclei and neutropenia are characteristics features of EBV infection

Question 13

What are the diseases caused by EBV?

Answer 13

Lacking- Oral hairy leukoplakia

Poor- Burkitt’s lymphoma, nasopharyngeal cancer, chronic fatigue syndrome, Hodgkin’s lymphoma

Normal- asymptomatic

Vigorous- Infectious mononucleosis

Question 14

What is the type of disease caused by HHV-5 (Cytomegalovirus) Infections?

Answer 14

Infected cells become abnormally large (owl’s eye)

One or more common infections of humans

Transmission occurs through bodily secretions- requires close contact and large exchange of secretion, usually occurs through sexual intercourse

Also transmitted by in utero exposure, vaginal birth, blood transfusions, and organ transplants

Most CMV infections are asymptomatic

Complications in fetuses, newborns, and immunodeficient patients

Treatment- formiversen

Question 15

What is the infection caused HHV-6?

Answer 15

In the genus Roseolovirus

Causes roseola

Characterized by pink rash on face, neck, trunk, and thighs

Question 16

What are is the infection caused by HHV8 (rhadinovirus)?

Answer 16

Associated with Kaposi’s sarcoma- cancer seen in AIDS patients

Rare and malignant neoplasia of blood and blood vessels, cancerous cells in the blood and blood vessels

Question 17

What are the common symptoms and characteristics of a Papillomavirus infection?

Answer 17

Cause papillomas, commonly known as warts, benign growths of the epithelium of skin or mucous membranes

Papillomas form on many body surfaces (seed warts, plantar warts, flat warts, and genital warts)

Genital warts can be giant cauliflower-like growths called condylomata acuminata, often painful and unsightly, associated with an increased rick of cancer

Transmitted via direct contact and via fomites

Autoinoculation-spreads from one location to another on a person

Question 18

How is a papillomavirus infection diagnosed, treated, and prevented?

Answer 18

Diagnosis- based on observation of papillomas, diagnose cancers by inspecting genitalaia and a PAP smear

Treatment- warts may be removed through various methods

Prevention- difficult to prevent warts, Gardasil vaccine (three doses for all females 11-26 yrs of age), effective against most strains of cervical cancer

Question 19

What are the characteristics of a polyomavirus infection?

Answer 19

Capable of causing tumors in animals and humans

May cause other diseases

BK and JC viruses initially infect lymphocytes

BK virus- potentially severe UTIs may develop

JC virus- can cause progressive multifocal leukoencephalopathy in which viruses can infect and kill oligodendrocytes of CNS, progressive reduction of brain function

Question 20

What are the characteristics of V. Adenoviridae?

Answer 20

Contain a single, linear dsDNA genome contained in a naked polyhedral capsid with spikes

One of the many causative agents of the “common cold”

Spread via respiratory droplets

Question 21

What are the types of infections caused by V. Adenoviridae?

Answer 21

Respiratory infection- viruses taken into cells lining the respiratory tract via endocytosis, symptoms include sneezing, sore throat, cough, headache, and malaise

In gastrointestinal tract can produce mild diarrhea

Infection of the conjunctiva can result in “pink eye”

Question 22

What are characteristics of Hepadnaviridae?

Answer 22

Enveloped DNA virus that invades and replicates in liver cells

Genome consists of both dsDNA and ssDNA

Includes Hepatitis B Virus (HBV)

HBV replicates through an RNA intermediary by using reverse transcriptase enzyme- unique among DNA viruses

Question 23

What are characteristics of a Hepatitis B infection?

Answer 23

Hepatitis- inflammation of the liver

HBV is the only DNA virus that causes hepatitis

Viral infection can cause severe liver damage- Coinfection with hepatitis D virus increases risk of permanent liver damage

Various symptoms- jaundice (bilirubin accumulates in the blood), liver enlargement, abdominal distress, bleeding into the skin and internal organs

Question 24

How is a Hepatitis B infection spread?

Answer 24

Virions are shed into saliva, semen, and vaginal secretions

Transmitted when infected body fluids contact breaks in the skin or mucous membranes

Virus spread through needles, sex, and childbirth

Many individuals are asymptomatic or have mild symptoms

HBV has been shown to be associated with liver cancer

Question 25

How is an HBV infection diagnosed, treated, and prevented?

Answer 25

Diagnosed- body fluids contain three types of virus particles, diagnose by detecting presence of viral antigens (dane, spherical, and filamentous particles)

Treatment- no universal effective treatment, Alpha-interferon (40% of cases), liver transplant required for end-stage chronic hepatitis B patients

Prevention- vaccine (3 doses), effective in 95% of individuals, safer sex

Question 26

What are characteristics of Parvoviridae?

Answer 26

Only human pathogen with a ssDNA genome, smallest of the DNA viruses

Causes a number of diseases in animals- B19 virus is the primary parvovirus in humans

Causes erythema infectiosum- fifth disease or slapping disease (behind 4 other diseases that cause a rash: scarlet fever, rubella, roseola, and measles)

Infection resulsts in the reddening of the skin beginning on the cheekc

Sunlight aggravates the condition