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WVSOM - Virus
Herpesviruses and Poxviruses
| Question | Answer |
|---|---|
| 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
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