Common Viral Pathogens Flashcards
What does HSV1 stand for?
Herpes simplex virus type I
HSV1 target cell type?
mucosal epi
HSV1 latency?
neuron (ganglia)
HSV1 transmission?
close contact
HSV1 clinical manifestations?
orofacial lesions, some genital lesions, encephalitis, herpes whitlow, herpes keratitis, neonatal herpes
HSV1 virus type?
ds DNA virus
HSV1 incubation period?
2-12 days (4 on avg)
What is the primary infection of HSV1?
first infection;
usu asymptomatic;
if symptoms present, they’re stronger than later;
no antibody present
What is the HSV1 latency period?
when virus is dormant in the body;
on trigeminal ganglion in facial disease;
on sacral ganglion in genital disease;
waits in the nucleus
What is the HSV1 reactivation phase?
virus emerges from latency and begins to replicate again
What are the signs/symptoms during the HSV1 reactivation phase?
orofacial, cornea (keratitis), or perineal (genital) lesions;
triggered by variety of events;
reactivation commonly asymptomatic or less severe than 1a infection
Why is herpes often spread unknowingly?
sometimes it’s asymptomatic during shedding phase, or the lesions are so small and trivial that they go unnoticed
What is gingivostomatitis?
symptomatic primary infection from HSV1;
ulcers on gums, lips, and tongue (anterior);
drooling;
fever;
lip and cervical lymph node swelling
What is herpetic whitlow?
transfer of virus from mouth to fingers via cuts or abrasions;
erythema, swelling, and grouped vesicles that grow into pustules with cloudy fluid;
tender to the touch
What is genital herpes?
usually HSV2 infection but HSV1 30% of the time;
painful vesicles and ulcers in genital and perianal region that last 10-14 days;
swelling; painful urination
What is herpes keratitis?
HSV infection of the cornea, usually by HSV1;
produces dendritic lesions of the cornea that can cause scarring and blindness (one of the leading causes)
What is encephalitis?
herpes infection of the brain; 1a or reactivation; bloodborne or neuronally spread; fulimant, hemorrhagic, necrotizing;
usu temporal lobes;
altered mental status and death results
What is neonatal herpes?
primary infection of a neonate acquired en utero, peripartum (most often), or postpartum;
mostly HSV2
What is the most common reactivation of HSV1?
herpes labialis (cold sores)
1a infection of any of the 3 branches of cranial nerve 5 (____, _____, or _____) leads to latent infection of nerve cells in the trigeminal ganglion.
ophthalmic, maxillary, mandibular
1a infection of any of the 3 branches of cranial nerve 5 (ophthalmic, maxillary, mandibular) leads to latent infection of nerve cells in the ______.
trigeminal ganglion
1a infection of any of the 3 branches of cranial nerve ____ (ophthalmic, maxillary, mandibular) leads to latent infection of nerve cells in the trigeminal ganglion.
five
Members of the ______ family all contain a ds-DNA genome that is protected by an icosahedral capsid and a glycoprotein-rich envelope.
Herpesviridae
Name the 3 viruses in the alpha subfamily and where they establish latency.
- HSV-1
- HSV-2
- VZV
sensory ganglia
Name the 3 viruses in the beta subfamily and where they establish latency.
- CMV
- HHV-6
- HHV-7
monocytes and lymphocytes
Name the 2 viruses in the gamma subfamily and where they establish latency.
- EBV
- KSHV
B cells
How does herpesvirus enter the cell?
binds to cell surface proteins, fuses to cell membrane, releases nucleocapsid into membrane where it travels to nucleus along microtubules
How is herpesvirus replicated?
- synthesis of intermediate early (IE) genes
- express early (E), which include DNA pol, thymidine kinase (TK), helicase
- express L genes, which encode structural proteins (capsids and glycoproteins)5
Where do herpesviruses obtain their envelopes?
from the Golgi
Members of the Herpesviridae family all contain a ____ that is protected by an icosahedral capsid and a glycoprotein-rich envelope.
ds-DNA genome
Members of the Herpesviridae family all contain a ds-DNA genome that is protected by _____ and a _____.
an icosahedral capsid; glycoprotein-rich envelope
What is the most common event in herpesvirus reactivation?
it’s asymptomatic, but viruses are shed
What does VZV stand for?
varicella zoster virus
VZV causes 2 clinical syndromes, ____ and ____.
Chickenpox (varicella); shingles (zoster)
Why is Chickenpox in pregnancy bad?
prego fem at high risk for developing varicella pneumonia and death
What are the s/s of chickenpox?
fever, headache, malaise;
rash appearing in crops or waves that starts on face or trunk and spreads to extremities;
vesicles to pustules that rupture and scab at all different times over 7 days
Pathogenesis of chickenpox?
enters via respiratory tract, spreads to lymphoid system where it replicates for 2-4 days.
1a viremia for 4-6 days, then the virus replicates in the liver and spleen.
2a viremia follows and spreads to skin where rash develops 14-16 days after exposure.
Name 6 chickenpox complications.
- 2a infection/cellulitis (group A strep infection of skin)
- pneumonia (bacterial from group A strep or viral in prego women or immunocompromised)
- necrotizing fasciitis (infection into the fascia that shears off nerve endings and blood supply from group A strep)
- encephalitis/encephalomyelitis (CNS infection via cross-reacting antibodies in immunocompromised)
- hepatitis (immunocompromised)
- congenital varicella syndrome (organ and tissue abnormalities in developing fetus when mom has chickenpox in 8th-20th week)
How is varicella treated?
usually none, but can give acyclovir; also live attenuated vaccines
How does VZV reactivate?
it tracks down the sensory nerve to the skin along a dermatome where it causes necrosis and inflammation of neurons
____ is the only herpesvirus that does not exhibit asymptomatic viral shedding.
VZV
How is VZV shed in shingles?
Only from the shingles lesions
What are the s/s of Shingles?
radicular pain preceding grouped vesicles on an erythematous base confined to a single dermatome that do not cross the midline
Name 3 ways to diagnose shingles (aside from clinically).
- direct fluorescent Ab
- VZV PCR
- viral culture
What is the treatment for shingles?
acyclovir and analgesics;
Zostavax vaccine
VZV is the only herpesvirus that does not exhibit ____.
asymptomatic viral shedding
What is congenital CMV?
babies born to mothers with a 1a CMV infection
What are the s/s of congenital CMV?
low birth weight, microcephaly, hearing loss, mental impairment, hepatosplenomegaly, skin rash (blueberry muffin) due to extramedullary hematopoiesis of the skin, jaundice, chorioretinits
What will be the serology test results in an acute primary CMV infection?
CMV IgM positive, IgG negative
What will be the serology test results in a pt that has never had a CMV infection?
negative IgM, negative IgG
What will be the serology test results in a pt that has had a CMV infection sometime in their life?
negative IgM, positive IgG
What will be the serology test results in a CMV reactivation?
positive IgM, positive IgG
What is the distinctive cytological finding in CMV?
owl’s eyes- dense, dark nuclear body surrounded by a halo in infected cells
What is the treatment for CMV?
usually none needed; immunocompromised get Ganciclovir or CMV-IG
How do T cells play a role in VZV?
lowered T cell immunity to varicella puts people at risk for shingles
