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USMLE Step 1 > Microbiology - Virus > Flashcards

Microbiology - Virus Flashcards

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1
Q

Adenovirus

A

Non-enveloped, linear dsDNA virus

Causes febrile pharyngitis, conjuctivitis, ARD, pneumonia, infectious keratitis, otitis media, sinusitis, acute hemorrhagic cystitis

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2
Q

Adenovirus (types 40 and 41)

A

Causes secretory protracted (1-2 weeks) diarrhea in children

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3
Q

All DNA viruses are double stranded with which exception?

A

Parvovirus is single stranded DNA (e.g. parvovirus B19) → replicates in the cytosol

All dsDNA viruses (except HBV) are infectious when purified → replicates in the nucleus

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4
Q

All RNA viruses are single stranded with the exception of…

A

Reovirus are double stranded RNA (e.g. rotavirus, coltivirus)

All RNA viruses replicate in the cytosol (except influenza virus and retroviruses)

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5
Q

BK virus

A

Polyomavirus

Non-enveloped, circular dsDNA virus

Seen in transplant patients, commonly targets the kidney

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6
Q

California encephalitis

A

Bunyavirus

Enveloped, helical, 3 segments of circular -ssRNA

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7
Q

Colorado tick fever virus

A

Reovirus 12 segments of dsRNA Not enveloped Wood tick

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8
Q

Crimean-Congo Hemorrhagic Fever

A

Bunyavirus

Enveloped, helical, 3 segments of circular -ssRNA

Hemorrhagic fever

Tx: ribavirin

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9
Q

Coronavirus

A

Coronavirus

Enveloped, helical, linear +ssRNA

Common cold

SARS (a/w masked palm civets, bats, ARDS, atypical pneumonia)

MERS (a/w camels)

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10
Q

Coxsackievirus

A

Picornavirus

Non-enveloped, icosahedral, linear +ssRNA

Type A causes herpangina, hand, foot, and mouth disease (rash on palms and soles), conjuctivitis

Type B causes pleurodynia

Either type can cause aseptic meningitis, myocarditis, pericarditis

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11
Q

Cytomegalovirus (CMV)/HHV-5

A

Herpesvirus

Enveloped, linear dsDNA virus

Atypical pneumonia, esophagitis (linear ulcerations in esophagus) in the immunosuppressed, retinitis (cotton-wool spots on funduscopic exam), mononucleosis-like syndrome (fever, fatigue, splenomegaly, aytpical lymphocytes ± sore throat, lymphadenopathy), congenital infection (periventricular calcifications, sensorineural hearing loss, seizures, blueberry muffin rash)

Nuclear and cytoplasmic inclusions in infected cells → “Owl Eyes” (see picture); latent in mononuclear cells

Binds to cellular integrins

No agglutination with serum heterophile antibodies (e.g. negative Monospot)

Tx: ganciclovir

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12
Q

Dengue

A

Flavivirus

Enveloped, icosahedral, linear +ssRNA

Bite of Aedes aegypti mosquito (arbovirus)

Infection with more than one of the 4 serotypes → hemorrhagic fever

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13
Q

Eastern/Western equine encephalitis

A

Togavirus

Enveloped, icosahedral, linear +ssRNA

Arbovirus

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14
Q

Ebola Virus

Marburg Virus

A

Filovirus

Enveloped, helical, linear -ssRNA

Pleomorphic shape

Hemorrhagic fever → often fatal

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15
Q

Epstein-Barr Virus (EBV)/HHV-4

A

Herpesvirus

Enveloped, linear dsDNA virus

Binds to CR2 (CD21)

Causes mononucleosis (fever, fatigue, hepatosplenomegaly, infects B cells but aytpical lymphocytes = cytotoxic T cells, exudative pharyngitis, cervical lymphadenopathy, esp. posterior cervical chain), endemic Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma

Agglutination with serum heterophile (horse, sheep) antibodies (e.g. Monospot); infection produces cold agglutinins

Risk of splenic rupture → avoid contact sports for 3 weeks

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16
Q

Equine Encephalitis

A

Togavirus

Enveloped, icosahedral, linear +ssRNA

Culex mosquito (arbovirus)

Flu-like illness, encephalitis

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17
Q

For which viruses are there live attenuated vaccines?

A

Live attenuated vaccines induce humoral and cell-mediated immunity but have a risk of reverting to virulence → no booster needed but avoid in immunocompromised and their close contacts

Vaccinia

Polio (Sabin)

Yellow fever

Measles, Mumps, Rubella

Rotavirus

Adenovirus

Varicella/Zoster

Small pox

Intranasal influenza

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18
Q

From which viruses are there killed vaccines?

A

Rabies

Polio (Salk = killed)

Influenza (injected)

Hepatitis A

Japanese encephalitis

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19
Q

From which viruses are there recomginant vaccines?

A

Hepatitis B (recombinant HBsAg)

HPV (types 6, 11, 16, 18)

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20
Q

Hantavirus

A

Bunyavirus

Enveloped, helical, 3 segments of circular -ssRNA

Contact with rodents

Hemorrhagic fever, pneumonia

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21
Q

Hepatitis A virus (HAV)

A

Picornavirus

Non-enveloped, icosahedral, linear +ssRNA

Fecal-oral transmission

Causes acute viral hepatitis

No carrier status or increased risk of hepatocellular carcinoma

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22
Q

Hepatitis B virus (HBV)

A

Hepadnavirus

Enveloped, circular dsDNA virus

Parenteral, sexual, maternal-fetal transmission

HBV DNA polymerase completes partial dsDNA → incorporated into host genome → host RNA polymerase makes mRNA → HBV DNA polymerase reverse transcribes mRNA into DNA to form new viral particle

Causes acute and chronic hepatitis; viral genome integrates into host genome → ↑ risk of hepatocellular carcinoma

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23
Q

Hepatitis C virus (HCV)

A

Flavivirus

Enveloped, icosahedral, linear +ssRNA

RNA-dependent RNA polymerase has no proof reading 3’→5’ exonuclear activity → mutations in envelope glycoproteins prevent immunity from infection or vaccines

Transmitted via blood (IVDU, post-transfusion), sex

Causes chronic inflammation → cirrhosis, hepatocellular carcinoma

Tx: INFα, ribavirin, sofosbuvir

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24
Q

Hepatitis D virus (HDV)

A

Delta virus

Enveloped, uncertain capsid shape, circular -ssRNA

Parenteral, sexual, maternal-fetal transmission

D for defective (requires HBV co-infection)

Superinfection (HDV following HBV) decreases prognosis

HDV must be coated by HBsAg to penetrate the hepatocyte

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25
Hepatitis E virus (HEV)
Hepevirus Non-enveloped, icosahedral, linear +ssRNA Fecal-oral transmission, esp with water-borne epidemics _High mortality in pregnant women_
26
Herpes Simplex Virus (HSV)
Herpesvirus Enveloped, linear dsDNA virus Infects mucosa epithelial cells → gingivostomatitis, herpes labialis, herpes genitalis, _spontaneous temporal lobe encephalitis_, keratoconjunctivitis, neonatal herpes (vesicular lesions, encephalitis) Latent in trigeminal ganglia or sacral ganglia Dx: viral culture, PCR of CSF, intranuclear Cowdry A inclusions, Tzanck smear (genital) showing multinucleated giant cells (see picuture) Tx: acyclovir, ganciclovir
27
HHV-8
Herpesvirus Enveloped, linear ds DNA virus Causes Kaposi sarcoma, neoplasm of endothelial cells (biopsy reveals _lymphocytic_ inflammation) Transmitted sexually
28
How to distinguish maculopapular rash of rubella from measles
Both rashes start in the face and spread downward Rubella rash involves the trunk Measles rash involves the trunk and limbs
29
HTLV
Retrovirus → reverse transcriptase Enveloped, icosahedral, linear +ssRNA Causes T-cell leukemia
30
Human Immunodeficiency Virus (HIV)
Retrovirus → reverse transcriptase Enveloped, conical, 2 copies of linear +ssRNA Viral gp120 targets CD4 and CCR5 (early) or CXCR4 (late) receptors on CD4+ T cells; targets CD4 and CCR5 on macrophages Causes AIDS when CD4 count \< 200 or HIV + AID-defining illness or CD4 % \< 14% Dx: ELISA (high sensitivity) if + → Western blot (high specificity)
31
Human Papilloma Virus (HPV)
Papillomavirus Non-enveloped, circular dsDNA virus HPV 1, 2, 6, 11 cause condylomata acuminata HPV 16, 18, 31 cause cancer of the cervix, penis, anus; virus expresses E6 and E7 which inactivates p53 and Rb, respectively, stimulating cell growth
32
Influenza virus
Orthomyxovirus Enveloped, helical, segmented linear -ssRNA Hemagglutinin promotes viral entry Neuraminidase promotes progeny virion release Patients at risk for fatal bacterial superinfection
33
Japanese Encephalitis
Flavivirus Enveloped, icosahedral, linear +ssRNA Birds and pigs are reservoirs Bite of Culex mosquito (arbovirus) Encephalitis Vaccine
34
JC Virus
Polyomavirus Non-enveloped, circular dsDNA Progresses to multifocal leukoencephalopathy (PML) in HIV
35
Lassa fever
Arenavirus --\> grainy appearance Enveloped, helical, 2 segments of circular -ssRNA Contact with mice/rats in W. Africa Hemorrhagic fever, hearing loss, pregnancy complications
36
Lymphocytic choriomeningitis virus (LCMV)
Arenavirus --\> grainy appearance Enveloped, helical, 2 segments of circular -ssRNA Contact with mouse, hamster excreta Biphasic illness
37
Measles
Paramyxovirus Enveloped, helical, linear -ssRNA F (fusion protein) causes respiratory epithelial cells to fuse (syncitia) 3 C's of measles: cough, coryza (catarrhal inflammation of the mucous membrane in the nose), conjunctivitis Koplik spots (red spots with blue-white center on buccal mucosa) precede descending maculopapular rash that involves trunk and _limbs_ (CTL response) Sequelae include: post-infectious encephalitis, acute disseminated encephalomyelitis (ADEM), measles inclusion body encephalitis (MIBE), subacute sclerosing panencephalitis (SSPE), giant cell pneumonia (in immunosuppressed/malnourished)
38
MMR Vaccine
Live-attenuated vaccine against measles, mumps, and rubella Rubella component may induce arthralgias
39
Molluscum contagiosum
Poxvirus → only type of DNA virus that replicates in the cytoplasm (has own DNA-dependent RNA polymerase) Enveloped, linear dsDNA virus Spreads in pools, gyms Flesh-colored dome lesions with central umbilicated dimple (see picture) Large eosinophilic cytoplsmic inclusions called molluscum bodies
40
Mumps
Paramyxovirus Enveloped, helical, linear -ssRNA F (fusion protein) causes respiratory epithelial cells to fuse (syncitia) Causes parotitis (elevated amylase), orchitis (usually unilateral, can cause infertility in teenagers), meningitis
41
Nipah/Hendra virus
Paramyxovirus Enveloped, helical, linear -ssRNA a/w bats, horses
42
Norovirus
Calcicivirus Non-enveloped, icosahedral, linear +ssRNA Leading cause of food borne disease Causes secretory diarrhea and vomiting More prevalent in older children and adults
43
Parainfluenza
Paramyxovirus Enveloped, helical, linear -ssRNA F (fusion protein) causes respiratory epithelial cells to fuse (syncitia) Causes croup (seal-like barking cough) Autumn epidemic
44
Parvovirus B19
Parvovirus Non-enveloped, linear _ssDNA_ virus Transmitted through respiratory droplets and infects RBC precursors Causes erythema infectiosum (prodrome → slapped cheek rash → lacy, reticular rash on trunk, extremities), aplastic crisis in people with chronic hemolytic anemia/sickle cell disease, hydrops fetalis, polyarthritis (esp. in adult women) Can cross placenta
45
Polio virus
Picornavirus Non-enveloped, icosahedral, linear +ssRNA Salk/IPV killed vaccine Sabin/OPV live vaccine
46
Rabies
Rhabdovirus Enveloped, helical, linear -ssRNA Binds to nicotinic acetylcholine receptors → retrograde travel through peripheral neurons to CNS Bullet-shaped Negri bodies in Purkinje cells of the cerebellum and hippocampus (show picture) Fever, malaise → agitation, photophobia, hydrophobia → paralysis, coma → death
47
Respiratory Syncytial Virus (RSV)
Paramyxovirus Enveloped, helical, linear -ssRNA F (fusion protein) causes respiratory epithelial cells to fuse (syncitia) Causes URI, croup, bronchiolitis, pneumonia in infants _Winter epidemic_ Tx: ribavirin, palivizumab (Ab against F protein) prevents pneumonia caused by RSV in premature infants
48
Rhinovirus
Picornavirus Non-enveloped, icosahedral, linear +ssRNA Causes the common cold
49
Roseola/HHV-6
Herpesvirus Enveloped, linear dsDNA virus High fevers for several days that can cause seizures followed by a diffuse maculopapular rash
50
Rotavirus
Reovirus Non-enveloped, double icosahedral, segmented linear **_ds_**RNA Most common cause of infantile diarrhea (secretory); villous destruction with atrophy leads to decreased absorption of sodium and loss of potassium _Winter_ seasonal pattern Reassortment (due to segmented genome) between related species can cause new strains
51
Rubella virus
Togavirus Enveloped, icosahedral, linear +ssRNA pH-dependent endocytosis Causes fever, _postauricular lymphadenopathy_, arthralgias, and fine rash that starts on the face and spreads to the trunk (first manifestation) Can cause TORCH infection in newborns (transplancental, esp. 1st trimester) --\> PDA/pulmonary artery hypoplasia, cataracts, deafness ± blueberry muffin rash Diagnose with nasal culture
52
Sandfly/Rift Valley fever
Bunyavirus Enveloped, helical, 3 segments of circular -ssRNA
53
Smallpox
Poxvirus Enveloped, linear dsDNA virus Brick-shaped virions Currently eradicated but can be used in germ warfare
54
St. Louis encephalitis
Flavivirus Enveloped, icosahedral, linear +ssRNA Arbovirus
55
Varicella Zoster Virus (VZV)/HHV-3
Herpesvirus Enveloped, linear dsDNA virus Primary infection = chickenpox; _vesicular lesions of different ages that starts on the trunk and spreads to face and extremities_ Recurrent infection = shingles; vesicular lesions in dermatomal distribution → post-herpetic neuralgia Latent in dorsal root or trigeminal ganglia
56
West Nile Virus
Flavivirus Enveloped, icosahedral, linear +ssRNA Birds are reservoir, bite of Culex mosquito (arbovirus) Flu-like symptoms, encephalitis
57
What viruses are associated with a maculopapular rash?
Measles Rubella Scarlet fever Roseola Parvovirus B19 Rash-associated enteroviruses
58
Which RNA viruses are positive-stranded ssRNA?
+ssRNA ≈ mRNA and are infectious when purified Retrovirus Togavirus Flavivirus Coronavirus Hepevirus Calcicivirus Picornavirus "I went to a _retro_ _toga_ party where I drank **_fla_**vored _Corona_ and ate _hippy_ **_Cali_**fornia **_pic_**kles"
59
Yellow fever
Flavivirus Enveloped, icosahedral, linear +ssRNA *Aedes aegypti* mosquito bite (arbovirus) High fever, black vomit, jaundice Live attenuated vaccine
60
What respiratory infections are associated with AIDS?
CMV pneumonia Aspergilllosis Pneumocystis peumonia --\> Pneumocystis jirovecii Pneumonia --\> S. pneumoniae TB-like disease --\> Mycobacterium avium-intracellulare (Mycobacterium avium complex [MAC])
61
What respiratory infections are associated with AIDS?
CMV pneumonia Aspergilllosis Pneumocystis peumonia --\> Pneumocystis jirovecii Pneumonia --\> S. pneumoniae TB-like disease --\> Mycobacterium avium-intracellulare (Mycobacterium avium complex [MAC])
62
What are dermatologic infections associated with AIDS?
Candidiasis of mouth, esophagus Hairy leukoplakia on lateral tongue --\> EBV Bacillary angiomatosis --\> Bartonella henselae
63
What are neurologic infections associated with AIDS?
Ring-enhancing lesions --\> Toxoplasma gondii Dementia Encephalopathy --\> JC virus reactivation Meningitis --\> cryptococcus neoformans Retinitis --\> CMV (cotton-wool spots)
64
What are oncologic disease associated with AIDS?
Non-Hodgkin lymphoma --\> EBV Primary CNS lymphoma --\> EBV Squamous cell carcinoma of rectum or cervix --\> HPV Kaposi sarcoma --\> HHV-8
65
What CSF findings are consistent with viral meningitis?
Normal/↑ opeing pressure ↑ lymphocytes Normal/↑ protein Normal glucose

USMLE Step 1 (20 decks)

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