Viruses Flashcards
Hepatitis A
- a non-enveloped, positive strand RNA virus of the picorna family
- water, food, close contact transmission
- 30d incubation period with insidious onset of nausea, fever, malaise, elevated LFT, and juandice
- jaundice and mortality increase with age
- diagnosed with IgM
- 2 part vaccine available
Hepatitis E
- a positive strand RNA virus of the hepe family
- outbreaks surround fecally contaminated water
- US cases usually have a history of travel
- mortality increases with age and pregnancy
- swine and avian reservoirs
- 40d incubation period
Hepatitis C
- a positive strand RNA virus of flavi family
- types Ia, Ib, 2, and 3 most common in the US
- transmitted percutaneously and permucosally
- replicates, assembles at membranous web, can spread through basolateral membrane
- 6-7 week incubation period but acute infection goes unnoticed
- high incidence of chronic infection
- alcohol, >40, HIV, HBV, male all increase morbidity
Describe the HepB genome.
- a relaxed circular DNA virus
- C gene encodes HBc and HBe antigens
- P gene encodes polymerase
- S gene encodes S, S1, S2
Hepatitis B
- a relaxed circular DNA virus of the hepadna family
- genome can integrate into host genome
- transmitted perinatally, parenterally, and sexually
- 60-90d incubation period
- chronic complications more common in those <5 y.o.
- complications: HCC, PAN, glomerulonephritis, cirrhosis
- pathology is immune mediated
Hepatitis D
- a ssRNA virus that replicates in the nucleus
- encodes only the gamma antigen
- reliant on HBV for surface antigen
- percutaneous and permucosal transmission
- co-infection more likely to resolve than superinfection
List the modes of transmission for each of the hepatitis viruses.
A: food, water, close contact B: sexual, perinatal, parenteral C: percutaneous, permucosal D: percutaneous, permucosal E: fecally contaminated water
List the common complications of Hepatitis B.
HCC, PAN, glomerulonephritis, cirrhosis
Hepatitis B pathology is mediated by what?
immune mediated
Which hepatitis virus assembles at the membranous web and can spread directly through the basolateral membrane of the host cell?
hepatitis C
Which hepatitis virus has a relaxed circular DNA genome?
hepatitis B
List the most common organisms associated with aseptic meningitis.
enteroviruses, primarily coxsackie A and B
Describe the presentation of aseptic meningitis.
- headache, neck stiffness, photophobia
- fever lasting five days
- rash, diarrhea, and cough common in young children
- rash is erythematous, maculopapular, and vesicular on the soles of the hands and feet and on mucous membranes
Poliovirus
- an serotype of enterovirus known to cause poliomyelitis
- has a tropism for the CNS but usually confined to oropharynx and gut
What are the three possible outcomes of a poliovirus infection?
- asymptomatic or mild illness
- non-paralytic poliomyelitis or aseptic meningitis
- paralytic poliomyelitis
Poliovirus targets which CNS cells.
autonomic and motor neurons of the anterior horn, pons, and medulla
What kind of vaccine is currently in use against poliovirus?
an inactivated vaccine
What happens in most cases of poliovirus infection?
90% of the time, the virus is confined to the gut and oropharynx and causes a mild illness of fever, malaise, and sore throat
The picornaviridae family includes what organisms?
it is a group of GI viruses include the enterovirus and hepatovirus genera
Describe the picornaviridae family genomes.
positive strand RNA viruses that yield a poly protein that must be cleaved
Describe the life cycle of picornaviruses.
- rapid- taken up via receptor mediated endocytosis
- inhibits cellular translation so it favors viral translation
- released by cell lysis
Which family of viruses has an incredibly rapid life cycle and inhibits host translation to favor viral translation?
picornaviruses
The enteroviruses is a species within the ___ family that includes which four serotypes?
- part of the picornaviridae family
- includes coxsackie A and B, poliovirus, and echovirus
The enteroviruses cause what diseases?
depending on the serotype:
- meningitis
- paralysis
- febrile exanthems
- ARD
- myocarditis
- orchitis
What role do secretory and serum antibodies play against enteroviruses?
secretory prevent initiation of infection while serum antibodies prevent viremic spread
What is the most common result of enteroviruses?
asymptomatic, mild URT disease, mild influenza-like disease
Enterovirus
- a species of the picorna family that includes coxsackie A and B, poliovirus, and echovirus
- enter via GI or respiratory tract and then enter lymphatics
- viral replication responsible for pathology
- rarely cause GI disease
- usually cause asymptomatic or mild flu-like illness
- can cause meningitis, orchitis, myocarditis, paralysis, ARD, or febrile exanthems
List the five GI virus families.
- picornaviridae
- rotaviridae
- caliciviridae
- astroviridae
- adenoviridae
Norwalk Virus
- a positive strand RNA GI virus of the caliciviridae family
- most common cause of gastroenteritis
- causes nausea, vomiting, anorexia, diarrhea, and headache after a 2-4 day incubation period
- common on cruise ships
- usually from contaminated food or water
- prevent with proper sanitation
What is the most common cause of gastroenteritis worldwide?
norwalk virus
Which virus is a common cause of GI problems on cruise ships?
norwalk virus
Describe the presentation of norwalk virus including incubation period.
- 2-4 day incubation period
- nausea, vomiting, anorexia, diarrhea, headache
Astroviridae
a family of GI viruses associated with endemic gastroenteritis in young children and neonates
What mediates enterovirus pathology?
viral replication
What is the most significant cause of infantile diarrhea?
the rotavirus family
Describe the structure of rotavirus and its genome.
- triple layer capsid (inner VP6 determines classification, outer VP4, VP7)
- dsRNA virus with 11 segments
What is the most common rotavirus?
group A, G1P[8]
How does rotavirus spread?
oral-fecal route
Describe the presentation of rotavirus infection.
- 2 day incubation period
- 7 days of osmotic diuresis with vomiting, fever, headache, and abdominal pain
How is rotavirus diagnosed?
via EIA or latex agglutination of stool sample
Describe the pathogenesis of rotavirus.
produces NSP4, an enterotoxin, and causes lysis of epithelial cells
Describe the rotavirus vaccine.
produced by human/bovine reassortment and meant only to prevent severe disease, not all disease
Rotavirus
- a family of segmented, dsRNA GI viruses
- triple layer capsid with VP6, VP4, VP7
- major cause of infantile diarrhea
- most common in those 6-24 months old in the cooler months
- 2 day incubation period followed by 7 days osmotic diuresis, vomiting, abdominal pain
- diagnosed via EIA or latex agglutination of stool sample
- vaccine available is only meant to limit severity
- pathogenesis relies on NSP4 enterotoxin and cell lysis- most common is group A G1P[8]
The first ever retrovirus identified was what?
Human T-cell Leukemia Virus 1
HTLV-1 infects what population of host cells?
CD4 T Cells
HTLV-1 is known to cause what diseases?
- asymptomatic infection in 95% of cases
- infection in early life results in adult T cell leukemia/lymphoma
- tropical spastic paraparesis
- HTLV-1 associated myelopathy
Where does HTLV-1 have a particularly high prevalence?
Japan
How is HTLV-1 primarily transmitted?
breast feeding
HTLV-1
- the first retrovirus discovered
- infects CD4 T cells
- transmitted via breast feeding but also sexually and via blood
- most infections are asymptomatic but may cause adult T-cell leukemia/lymphoma, tropical spastic paraparesis, or HTLV-1 associated myelopathy
Describe the genome of HIV-1.
a diploid RNA retrovirus with 3 major genes: env, pol, gag
HIV-1 targets which host cell population?
CD4 T cells and those of monocyte/macrophage lineage
How does HIV-1 enter target cells?
gp41 and gp120 interact with host CD4 TCR and CCR5 or CXCR4 co-receptors
How is HIV-1 transmitted?
via blood, intercourse, and perinatally
Describe an acute HIV-1 infection.
headache, myalgia, swollen lymph nodes, CNS findings, pneumonitis, and diarrhea lasting weeks
Why does HIV-1 often cause diarrhea during acute infection?
because it has a tropism for GALT
What happens to CD4, CD8, and p24 levels during acute HIV-1 infection?
- CD4 levels drop
- CD8 levels rise
- p24 antigen levels rise in the blood
What is the average time between acute HIV-1 infection and AIDS onset?
ten years
What defines AIDS?
- a CD4 count below 200 cells/uL
- or an AIDS defining illness
Mycobacterial Disease
- a reactivation of M.tb or M. avium complex in HIV patients
- M.tb associated with pneumonia
- MAC associated with disseminated disease in HIV patients
How does P. jiroveci related to HIV patients?
- all HIV patients given TMP-SMX as prophylaxis
- causes a severe pneumonia
The most common fungal infection in HIV patients is what?
candidiasis
How does candidiasis present?
white plaques with a “stuck on” appearance found on the tongue, palate, esophagus, or vagina of immunocompromised patients
Hairy Leukoplakia
a disease caused by EBV in AIDS patients and generates a large white patch on the tongue
Taxoplasmosis
an opportunistic infection acquired from undercooked meat or cat feces that causes CNS disease in HIV patients
Describe the presentation of taxoplasmosis.
- a CNS disease
- headache, confusion, weakness, and fever
- MRI reveals a ring enhancing lesion
Ring enhancing lesions on MRI are characteristic of what illness?
taxoplasmosis infection
Cryptococal Meningioencephalitis
- a cryptococcus neoformans infection common in those with a CD4 count below 100 cells/uL
- presents with subacute fever, malaise, headache, stiff neck, and photophobia
- diagnose with CSF analysis and culture
What organism causes cryptococcal meningoencephalitis?
cryptococcus neoformans
How is cryptococcal meningoencephalitis diagnosed?
CSF analysis and culture
Who is cryptococcal meningoencephalitis most likely to affect?
those with a CD4 count below 100 cells/uL
How do we define AIDS-related dementia complex?
a score of more than 2 SD below mean within two cognitive domains along with ADL impairment
What 5 gross and histologic findings are consistent with AIDS-related dementia complex?
- white mater pallor
- microglial nodules
- multinucleated giant cells
- perivascular infiltrate
- frontal and temporal lobe neuron loss
Describe the genome of herpesviridae viruses.
- a family of dsDNA viruses
- genome has an L and S region, each bordered by inverted repeats
- transcription is temporal with alpha, beta, and gamma genes encoding transcription regulators, DNA replicators, and structural components, respectively
All herpes viruses are capable of what?
latency
Herpesviridae
- a family of dsDNA viruses that utilize temporal transcription
- three subfamilies include alpha, beta, and gamma
- capable of forming syncytia
- enter cells via fusion, capsids forming nucleus and leave via double envelopment process, causes cell lysis
Describe the herpesviridae life cycle.
- enter via fusion event
- transcription of genome via host RNA pol II in nucleus
- capsid assembles in the nucleus
- capsid leaves via a double envelopment proccess
- acquires an envelop from the golgi
- leaves the cell via lysis
How are HSV-1 and HSV-2 primarily spread?
- HSV-1 via oral contact and saliva
- HSV-2 via sexual contact or autoinoculation
HSV-1
- a dsDNA virus of the alpha herpesviridae subfamily
- spread primarily via saliva
- infects mucoepithelial cells
- remains latent in trigeminal ganglia or DRG and reactivated by stress, light, immunosuppressants
- typically cause oral lesions but also cause encephalitis, keratoconjunctivitis, herpes whitlow, and herpes gladitorium
Where does HSV-1 typically remain latent?
the trigeminal ganglia or DRG
HSV-1 causes what diseases?
- primarily herpes labials (cold sore)
- also encephalitis, keratoconjunctivitis, herpes whitlow, and herpes gladitorum
Describe the presentation of a cold sore.
- pain, tingling, and itching followed by the appearance of erythema and edema
- papule and vesicles form within 24 hours
- ulcerates and heals 7-10 days later
HSV-2
- a dsDNA virus of the alpha herpesviridae subfamily
- primarily spread via sexual contact
- usually found latent in sacral ganglia
- most commonly causes genital lesions
- also causes encephalitis, pharyngitis, herpes whitlow, and neonatal herpes
Where does HSV-2 usually reside latent?
sacral ganglia
What diseases does HSV-2 cause?
- usually genital lesions
- also encephalitis, pharyngitis, herpes whitlow, and neonatal herpes
Describe an acute genital herpes infection.
- incubation period of 5 days
- tender lymph nodes, fever, dysuria, itching
- followed by lesions
- resolves 3-4 weeks later with recurrences being shorter
Eczema Herpeticum
a herpes infection of children with pre-existing atopic dermatitis and burn patients which spreads cutaneous
Herpes Whitlow
an infection of the hands and wrists from body fluids or open sores infected by either HSV-1 or HSV-2
Herpes Gladitorum
a superficial skin lesion caused by HSV-1, most commonly on the feet of wrestlers
Herpes Keratoconjunctivitis
a monocular conjunctival infection by HSV-1 that my cause corneal damage and blindness with recurrent infection
What is the most common cause of sporadic encephalitis?
herpes infection
Herpes encephalitis affects which brain regions most?
temporal and inferior frontal lobes
How does herpes encephalitis present?
with fever, confusion, seizures, and coma
What is the significance of Cowdry Type A inclusion bodies?
they are herpes inclusion bodies present in the histology of herpes encephalitis
Neonatal Herpes
- a usually fatal infection by HSV-2 acquired in utero, usually during a primary infection of the mother
- spreads to liver, lungs, and CNS because the immune system isn’t fully developed
- causes brain atrophy
Which organs are most affected by neonatal herpes?
liver, lungs, and CNS
Describe the gross pathology of neonatal herpes.
- brain atrophy
- disseminated yellowish necrotic liver lesions
What is the peak incidence of Varicella-Zoster virus infection?
age 2-6
Describe the spread of VZV in humans.
- transmitted via droplets to the respiratory tract
- carried by lymphatics to the blood
- then onto the skin and mucous membranes
Where does VZV typically remain latent?
sensory ganglia
What kind of vaccine is the VZV vaccine?
a live, attenuated vaccine
What is zostavax?
a zoster vaccine given to those over the age of 60
Describe congenital varicella?
a varicella infection acquired in utero that causes scaring of skin, limb hypoplasia, and CNS defects
EBV
- a gammaherpes virus spread via saliva
- targets B cells
- three outcomes: active infection, latent infection, immortalization and cancer
- has four latency programs depending on the expression profile of nine genes, each program causes a different set of diseases
What are Downey cells?
abnormally activated lymphocytes associated with EBV infection and transformation of B cells
How is EBV spread?
via saliva
What are the three outcomes associated with an EBV infection?
- active infection
- latent infection
- stimulation and immortalization of B cells to cause cancer
EBV targets what human cell population?
B cells
How does EBV cause lymphoma/leukemia?
its 9 latency genes interfere with cellular control and differentiation of B cells
What causes infectious mononucleosis?
EBV infection
Heterophil antibodies are associated with what illness?
EBV infection
Describe the presentation of infectious mono.
- cervical lymphadenopathy
- splenomegaly
- exudative pharyngitis
- hepatomegaly
- presence of heterophil antibodies and downey cells
What are the complications of infectious mono.
- CNS complications
- ruptured spleen
- laryngeal obstruction
The severity of mono correlates with what?
the age of infection with younger being associated with milder illness
Burkitt’s Lymphoma
- a cancer of the lymphatic system
- comes in three types: endemic, sporadic, and HIV-1 associated
- all forms associated with a translocation of chromosome 8 in the region of c-myc and chromosome 14 or 22
What is unique about endemic Burkitt’s lymphoma?
- associated with EBV infection
- usually seen in those 2-14 living in equatorial Affrica
What is the most common form of Burkitt’s lymphoma in the US?
sporadic
What tumor types are endemic, sporadic, and HIV-1-associated Burkitt’s lymphoma associated with?
- endemic: extra nodal tumors
- sporadic and HIV-1: lymph node tumors
Burkitt’s lymphoma is associated with what genetic factor?
a translocation of chromosome 8 around the region of c-myc with either chromosome 14 or 22
EBV is associated with which lymphomas and leukemias?
- Hodgkins lymphoma
- hairy oral leukoplakia
- African Burkitt’s lymphoma
What is Hodgkin’s lymphoma? Which age group is most affected?
- a rare lymphoma in the US associated with EBV
- affects those 16-34 and those over 55
What are Reed-Stenberg cells?
cells associated with Hodgkin’s lymphoma that have a B cell origin
What is the most common virus transmitted to fetuses?
CMV