DD- COMMON VIRAL PATHOGENS Flashcards
8 herpesviruses which infect humans
-Herpes simplex virus, type 1 and type 2 (HSV1, HSV2)
– Varicella-zoster virus (VZV)
– Cytomegalovirus (CMV)
– Epstein-Barr virus (EBV)
– Human herpesvirus 6 (HHV6)
– Human herpesvirus 7 (HHV7)
– Human herpesvirus 8 (HHV8)/KSHV
Herpesviridae: Following primary infection, the virus establishes a______ in the host (location depends on subfamily) and may reactivate at a later time
latent infection
Human herpesvirus 8 (HHV8)/KSHV
herpesviruses which infect humans
Herpesvirus structure
Enveloped
- Derived from host membrane
-Virally-encoded glycoproteins are important for binding to host cells
Human herpesvirus 6 (HHV6)
herpesviruses which infect humans
Herpesvirus structure- Tegument
Contains proteins that are fully formed and active and control viral entry, gene expression, and immune evasion
Epstein-Barr virus (EBV)
herpesviruses which infect humans
HSV1 and HSV2
Both viruses cause painful vesicles on the ______ at the site of inoculation
skin
Cytomegalovirus (CMV)
herpesviruses which infect humans
HSV1 is usually associated with _____ lesions
orofacial
Varicella-zoster virus (VZV)
herpesviruses which infect humans
HSV2 is usually associated with
genital lesions (genital herpes)
Herpes simplex virus, type 1 and type 2 (HSV1, HSV2)
herpesviruses which infect humans
Transmission of HSV usually occurs through close contact with a person who is shedding virus at
a mucosal surface
in genital/oral secretions
Clinical Patterns of HSV Disease
Most primary infections with HSV are silent
Primary HSV-1 infection usually occurs during childhood
Primary HSV-1 infection usually occurs during______
childhood
Gingivostomatitis
common infection of the mouth and gums
Most common symptomatic infection
Clinical Patterns of HSV Disease
Herpetic whitlow
a lesion (whitlow) on a finger or thumb caused by the herpes simplex virus.
Occupational hazard for doctors, dentists, nurses
Clinical Patterns of HSV Disease
Encephalitis
Inflammation of the brain, often due to infection
_____most common cause of encephalitis in US
HSV
Herpes keratitis
Inflammation/infection of the cornea, leading to pain absence of trauma
HSV reaches the cornea via the ophthalmic branch of the ______
trigeminal nerve
Genital Herpes
Lesions last 10-14 days; usually very painful
Distinct from ulcers caused by syphilis (single hard painless
ulcer) and chancroid (soft painful ulcers associated with swollen inguinal lymph nodes)
Neonatal HSV
Serious disease transmitted to a newborn
3 forms:
- Skin, eye and mucous membrane disease (SEM)
- CNS
- Disseminated
Following primary infection, HSV enters sensory nerve
endings and travels up the axon and establishes a latent
infection in:
sensory ganglia (alphaherpesvirus)
Reactivated lesions are infectious and people often continue to shed virus for a period of time_____ the lesions are healed
after
Definitive diagnosis of herpes can be obtained by:
– Viral culture of lesions
– Direct IFA of lesions
– PCR of lesions
Oral antiviral therapy (______ or a related antiviral) can be used for oral or genital HSV outbreaks
acyclovir
_____ is recommended for pregnant women with active
genital lesions at time of delivery
C-section
Prophylactic antiviral suppressive therapy has been shown to decrease outbreaks and viral shedding so is used in some patients, particularly with ______
genital herpes
Varicella-Zoster Virus
Varicella or chickenpox
highly contagious
acyclovir
Oral antiviral therapy can be used for oral or genital HSV outbreaks
Varicella-Zoster Virus
Transmission: highly contagious
– Primarily respiratory via droplet or aerosolized
secretions (coughing, sneezing)
– Contact with lesions
Varicella
The classic rash consists of lesions in multiple stages of development on any one part of the body (i.e. vesicles, pustules, scabs/crusts)
Complications of varicella
Pregnant women and immunocompromised patients are at high risk for morbidity and mortality
_____ has been shown to accelerate the
resolution of chickenpox if the patient presents
within 48-72 hours of onset
Acyclovir
__________vaccine is currently recommended for prevention of chickenpox
Live attenuated varicella
VZV is the only herpes virus in which asymptomatic viral shedding ______-in normal hosts who experience reactivation
does not occur
Herpes zoster or shingles:
occurs in 30% of individuals from
Varicella
Post-herpetic neuralgia
PHN
complication of shingles, which is caused by the chickenpox (herpes zoster) virus
Post-herpetic neuralgia
PHN
Debilitating neuropathic
pain that can last weeks to
months
Immune response to VZV
-Cell mediated immunity to VZV decreases w/ age
– Incidence of shingles much higher in the elderly and
immunocompromised
– Persons with low cell mediated immunity to VZV at higher risk for VZV reactivation (shingles)
Cell mediated immunity to VZV is an important determinant
in who is at risk for
shingles
Diagnosis, Chickenpox and shingles are diagnosed
clinically or
– Direct IFA
– HSV and VZV PCR
– Viral culture
For shingles, acyclovir given within ______ of onset may decrease lesions and pain
48-72 hours
Cytomegalovirus
– Almost all are asymptomatic
Primary infection in immunocompromised persons is serious and CMV can infect most organs (CMV retinitis and colitis in HIV patients)
Cytomegalovirus Transmission
A person can become infected with CMV when they
come in contact with infected body fluids
CMV infects the ___________, resulting in a persistent infection and intermittent viral shedding
epithelial cells of the salivary gland or the genital tract
Congenital CMV Syndrome
- Low birth weight
- Microcephaly
- Hearing loss
- Mental impairment
- Hepatosplenomegaly
- Skin rash (blueberry muffin spots)
- Jaundice
- Chorioretinitis
Neonate viral syndromes
neonatal HSV, or congenital VZV and
CMV syndromes.
Most common symptomatic primary infection that occurs with HSV-1 infection.
Gingivostomatitis
condition where HSV infects the cornea of the eye
Herpes keratitis
can be the result of a primary infection or from reactivation
Low birth weight Microcephaly Hearing loss Mental impairment Hepatosplenomegaly Skin rash (blueberry muffin spots)-due to extramedullary hematopoiesis in the skin Jaundice Chorioretinitis
Congenital CMV Syndrome
This is an extremely serious manifestation of herpes disease.
Encephalitis
-can be caused by primary disease or reactivation.
Herpes encephalitis can occur either through
blood-borne (hematogenous) spread or ___________ of the virus.
neuronal transmission
Herpes infection of the brain results in a fulminant and hemorrhagic, ________.
There is a strong predilection for the temporal lobes of the brain.
necrotizing encephalitis
Mortality is about 30% with treatment. HSV-1 causes most cases of childhood and adult.
HSV-2 is the more common cause of neonatal herpes, Associated with maternal genital herpes infections.
Encephalitis
Gingivostomatitis is common in
HSV-1
Herpes Keratitis is occasional in
HSV-1
“Other” virus tests (when clinical doesn’t work)
Viral culture of lesions
Direct fluorescent antibody stain of lesions
PCR of lesions (most expensive)
Chicken pox (varicella) is a highly contagious and common childhood disease, which is now preventable by vaccination. Chickenpox is primarily transmitted by the _____________ via droplet or aerosolized secretions (coughing, sneezing).
respiratory route
Incubation period: It takes from ________ after exposure for someone to develop chickenpox.
10-21 days
The initial lesions of_______ might be flat and rose
colored, but they quickly mature into the classic “dew drop on a rose petal” which is a vesicle on an erythematosus base
Chicken pox (varicella)
Pathogenesis of Chickenpox- The virus gains entry via the respiratory tract and spreads to the regional_______.
lymphoid system