Chapter 24- Pathogenic DNA Viruses Flashcards
What are some general characteristics of the Poxviridae family?
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
What are the stages of the formation of a lesion of a poxvirus infection?
- Macule- reddened skin
- Papule- rising of reddened area
- Vesicle- fills with fluid
- Pustule- fills with pus
- Forms a crust
- Scar forms
What are some general characteristics of smallpox?
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?
How could smallpox be eradicated?
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
What are characteristics of the disease Molluscum Contagiosum?
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
What are some characteristics of Herpesviridae?
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
What are characteristics of the infections caused by HHV1 and HHV2?
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
What are the specific diseases caused by HHV1 and HHV2 and their characteristics?
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
What are the types of infections caused by HHV3?
Varicella-Zoster Virus
2 Diseases
Varicella- often called chicken pox, affects children usually
Herpes zoster- also called shingles, usually occurs in adults
What are the characteristics of chicken pox and shingles?
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
How is an HHV3 virus infection diagnosed, treated, and prevented?
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
What are some general characteristics of HHV4?
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
What are the diseases caused by EBV?
Lacking- Oral hairy leukoplakia
Poor- Burkitt’s lymphoma, nasopharyngeal cancer, chronic fatigue syndrome, Hodgkin’s lymphoma
Normal- asymptomatic
Vigorous- Infectious mononucleosis
What is the type of disease caused by HHV-5 (Cytomegalovirus) Infections?
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
What is the infection caused HHV-6?
In the genus Roseolovirus
Causes roseola
Characterized by pink rash on face, neck, trunk, and thighs
What are is the infection caused by HHV8 (rhadinovirus)?
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
What are the common symptoms and characteristics of a Papillomavirus infection?
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
How is a papillomavirus infection diagnosed, treated, and prevented?
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
What are the characteristics of a polyomavirus infection?
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
What are the characteristics of V. Adenoviridae?
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
What are the types of infections caused by V. Adenoviridae?
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”
What are characteristics of Hepadnaviridae?
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
What are characteristics of a Hepatitis B infection?
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
How is a Hepatitis B infection spread?
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
