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WVSOM - Virus

Herpesviruses and Poxviruses

QuestionAnswer
Description of herpes viruses ds DNA, icosahedral, enveloped, intranuclear inclusion bodies, multinucleated giant cells, budding virus
Name 2 groups of herpes viruses Neurotropic & lymphotropic
What areas are neurotropic herpes viruses associated with? Skin, mucous membranes, nervous system
List the 2 specific viruses within the neurotropic herpes virus group Herpes simplex viruses 1,2 (HSV-1,2) and varicella-zoster virus (VZV)
List the 4 specific viruses within the lymphotropic herpes virus group Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpes virus type 6,7 (HHV-6 = roseolovirus), human herpes virus type 8 (HHV-8, KSHV = Kaposi's sacrcoma herpes virus)
What are some specific characteristics of herpes virus? Lifelong infection, latency, reactivation causing recurrent diseases, reactivation under immunosuppression, latency-associated RNA transcript, latent virus DNA tethered
What 2 herpes viruses can reactivate to cause recurrent disease? HSV-1 and VZV
What 2 herpes viruses can reactivate under immunosuppressive conditions? CMV and EBV (B-cells)
What does latent-associated RNA transcript mean? That it is continually expressed and can influence cellular functions
"free" DNA Refers to latent virus that exists as nuclear "extra-chromosomal" DNA tethered to host DNA
Diseases caused by herpes simplex virus-1 Encephalitis, conjunctivitis, gingiostomatitis, tonsilitis, labialis, pharyngitis, esophagitis, herpes gladiatorum, tracheobronchitis, genital herpes, herpes whitlow
Diseases caused by herpes simplex virus-2 Meningitis, gingiostomatitis, tonsilitis, labialis, pharyngitis, perianal herpes, genital herpes, herpes whitlow
What is gingiostomatitis? Initial HSV-1 infection; infects mucous membranes (mouth); primary infection in children; pain, soreness, fever associated with disease
What is herpes labialis? "cold sores"; around the lips; reactivation of latent virus (due to disease, trauma); recurrent in adolescents / adults
Keratoconjunctivitis HSV-1,2; affects the cornea and conjunctiva; recurrent infection; can lead to blindness
Eczema herpeticum Primary infection around pre-existing eczema / dermatitis
Meningoencephalitis Meningitis & encephalitis occur at same time; can be recurrent or primary; can follow skin, oral, genital, ocular infection
Who gets herpes gladiatorum? Wrestlers
Who gets herpetic whitlow? Health care professionals
What herpes virus follows an allergic reaction? Erythema multiforme minor
What is the characteristic lesion of erythema multiforme minor? "bull's eye" or "target" lesion
How does erythema multiforme develop? Infection results in HSV DNA fragments deposited -> macrophages consume fragments -> travel to other areas of body (i.e. skin) -> fight infection there, but deposit HSV fragments -> attract T-cells -> release INFs, ILs -> result = lesion
When is HSV-1 typically acquired? Childhood (75% btw ages 1-3)
Via what route is HSV-1 typically acquired? Oral secretions
What controls HSV-1 symptoms? The immune system (NOT the retention of the virus)
Primary transmission (symptomatic / asymptomatic) Asymptomatic
What % of individuals experience asymptomatic recurrance of HSV-1? 60%
What are the 2 types of HSV-1 recurrances / reactivations? Symptomatic, asymptomatic
HSV-1 infections make up what % of genital HSV? 40%
What does VZV cause? Chickenpox
What does EBV cause? Mononucleosis
Lymphotropic herpes viruses usually develop rashes, why? Deposition of immune complexes
Where do neurotropic herpes viruses grow? On the skin
Where do lymphotropic herpes viruses lay dormant? T, B cells, macrophages
HSV-1,2 typically cause what types of infections? Oral (HSV-1), genital (HSV-2)
Varicella virus develops what disease? Chickenpox
Zoster virus develops what disease? Shingles (reactivation)
Initial infection site of varicella-zoster virus Upper respiratory tract
Where does varicella-zoster virus initially grow? Lymph nodes
How does varicella-zoster virus eventually present with lesions on the skin? Virus amplified in other organs after leaving lymph nodes -> travels to blood -> reaches skin = chickenpox
Time-frame for visualization of varicella-zoster lesions 2 weeks
How long do varicella-zoster lesions last? 3-5 days -> crust -> fall off (usually w/o scarring)
Chickenpox Varicella virus; primary infection; children; results in fluid-filled vesicles; itchy, scratchy; be aware of bacterial infection; becomes dormant along nerve
Shingles Zoster virus; reactivation of latent virus; adults; occurs along dermatome; thoracic, trigeminal; unilateral; associated with inflammation = post-herpetic neuralgia (pain) -> can last a long time; complications in immunocompromised
Stages of zoster infection Vesicles -> pustules -> crusts -> ulcers (due to bacterial infection)
What disease process results from contact with varicella-zoster virus lesions or droplet transmission? Chickenpox (NOT shingles)
Typically, how many times does zoster usually reactivate? Once; in the elderly or immunocompromised
Why has the incidence of varicella-zoster virus (chickenpox and shingles) decreased? Due to vaccine
What are the different types of human herpes virus? HHV-6,7,8
What are some other names for HHV-6? Roseola, sixth disease, exanthem subitum
Characteristics for HHV-6 Fever and rash; rash not due to virus, rather due to high temperatures
What age group does HHV-6 mostly affect? 6 months - 3 years
What are some complications of HHV-6? Encephalitis, hemophagocytic syndrome
HHV-7 Much less common; aka roseola
HHV-8 is what type of virus? Tumor virus
How is HHV-8 transmitted? Orally, sexually
Who typically contracts HHV-8? Immunosuppressed individuals
What does HHV-8 cause? Kaposi's sarcoma
What is the target for herpes virus treatment? Viral DNA polymerase
How is herpes virus diagnosed? Clinical symptoms; virus isolation; identification; rise in Ab titer; CF; neutralization; immunofluorescent; rapid ELISA; PCR; immunoblot
What type of vaccine is used against chickenpox? Live, attenuated vaccine
What vaccine is available for the immunosuppressed and for neonates? VariZIG (varicella-zoster immune globulin)
Features of poxviruses ds DNA; complex; unique structure, size; surrounded by membrane; nucleoid; lateral bodies; largest (physically & genetically)
How many types of poxviruses cause human disease? 9
What are the 2 most significant poxviruses that cause human disease? Smallpox & molluscum contagiosum
What causes smallpox? Variola virus
What infectious agent has been eradicated from the world? Variola virus (causes smallpox)
What are the major and minor virus strains of smallpox? Variola virus (major) & alastrim virus (minor)
How is the smallpox vaccine used these days? As an experimental vector for delivery of genes for mutational correction
Is the variola virus specific to humans? YES
How is variola virus spread? By inhalation
How long is the incubation period of variola virus? 12-14 days
What develops 17 days post variola virus infection? Macular rash
What is the progression of lesions in a variola virus infection? Papular -> vesicular -> pustular
Mortality rate of variola virus infection 30%
Why does scarring develop with a variola virus infection? Due to bacterial infection of lesions
Is treatment required for smallpox? NO
How is the smallpox vaccine delivered? Via a bifurcated needle that scratches the surface of the skin and deposits the virus on the skin
Besides smallpox, name 3 other common poxvirus skin infections Molluscum contagiosum, orf, milker's nodules
Who does molluscum contagiosum mainly affect? Children
How is molluscum contagiosum acquired? Direct contact, fomites (inanimate objects), sexual contact
What is the clinical presentation of molluscum contagiosum? Papular eruption
Who develops orf? Farmers
How do farmers acquire orf? From sheep or goats
What is the clinical presenation of orf? Blister-like eruption
What causes milker's nodules? Who acquires milker's nodules? Paravaccinia virus; diary farmers, butchers
Created by: JaneO