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USMLE Step 1 > Microbiology - Virus > Flashcards

Microbiology - Virus Flashcards

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USMLE® Step 1 flashcards
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
Q

Hepatitis E virus (HEV)

A

Hepevirus

Non-enveloped, icosahedral, linear +ssRNA

Fecal-oral transmission, esp with water-borne epidemics

High mortality in pregnant women

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26
Q

Herpes Simplex Virus (HSV)

A

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

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27
Q

HHV-8

A

Herpesvirus

Enveloped, linear ds DNA virus

Causes Kaposi sarcoma, neoplasm of endothelial cells (biopsy reveals lymphocytic inflammation)

Transmitted sexually

28
Q

How to distinguish maculopapular rash of rubella from measles

A

Both rashes start in the face and spread downward

Rubella rash involves the trunk

Measles rash involves the trunk and limbs

29
Q

HTLV

A

Retrovirus → reverse transcriptase

Enveloped, icosahedral, linear +ssRNA

Causes T-cell leukemia

30
Q

Human Immunodeficiency Virus (HIV)

A

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
Q

Human Papilloma Virus (HPV)

A

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
Q

Influenza virus

A

Orthomyxovirus

Enveloped, helical, segmented linear -ssRNA

Hemagglutinin promotes viral entry

Neuraminidase promotes progeny virion release

Patients at risk for fatal bacterial superinfection

33
Q

Japanese Encephalitis

A

Flavivirus

Enveloped, icosahedral, linear +ssRNA

Birds and pigs are reservoirs

Bite of Culex mosquito (arbovirus)

Encephalitis Vaccine

34
Q

JC Virus

A

Polyomavirus

Non-enveloped, circular dsDNA

Progresses to multifocal leukoencephalopathy (PML) in HIV

35
Q

Lassa fever

A

Arenavirus –> grainy appearance

Enveloped, helical, 2 segments of circular -ssRNA

Contact with mice/rats in W. Africa

Hemorrhagic fever, hearing loss, pregnancy complications

36
Q

Lymphocytic choriomeningitis virus (LCMV)

A

Arenavirus –> grainy appearance

Enveloped, helical, 2 segments of circular -ssRNA

Contact with mouse, hamster excreta

Biphasic illness

37
Q

Measles

A

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
Q

MMR Vaccine

A

Live-attenuated vaccine against measles, mumps, and rubella

Rubella component may induce arthralgias

39
Q

Molluscum contagiosum

A

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
Q

Mumps

A

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
Q

Nipah/Hendra virus

A

Paramyxovirus

Enveloped, helical, linear -ssRNA

a/w bats, horses

42
Q

Norovirus

A

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
Q

Parainfluenza

A

Paramyxovirus

Enveloped, helical, linear -ssRNA

F (fusion protein) causes respiratory epithelial cells to fuse (syncitia)

Causes croup (seal-like barking cough)

Autumn epidemic

44
Q

Parvovirus B19

A

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
Q

Polio virus

A

Picornavirus

Non-enveloped, icosahedral, linear +ssRNA

Salk/IPV killed vaccine

Sabin/OPV live vaccine

46
Q

Rabies

A

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
Q

Respiratory Syncytial Virus (RSV)

A

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
Q

Rhinovirus

A

Picornavirus

Non-enveloped, icosahedral, linear +ssRNA

Causes the common cold

49
Q

Roseola/HHV-6

A

Herpesvirus

Enveloped, linear dsDNA virus

High fevers for several days that can cause seizures followed by a diffuse maculopapular rash

50
Q

Rotavirus

A

Reovirus

Non-enveloped, double icosahedral, segmented linear dsRNA

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
Q

Rubella virus

A

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
Q

Sandfly/Rift Valley fever

A

Bunyavirus

Enveloped, helical, 3 segments of circular -ssRNA

53
Q

Smallpox

A

Poxvirus

Enveloped, linear dsDNA virus

Brick-shaped virions

Currently eradicated but can be used in germ warfare

54
Q

St. Louis encephalitis

A

Flavivirus

Enveloped, icosahedral, linear +ssRNA

Arbovirus

55
Q

Varicella Zoster Virus (VZV)/HHV-3

A

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
Q

West Nile Virus

A

Flavivirus

Enveloped, icosahedral, linear +ssRNA

Birds are reservoir, bite of Culex mosquito (arbovirus)

Flu-like symptoms, encephalitis

57
Q

What viruses are associated with a maculopapular rash?

A

Measles Rubella Scarlet fever Roseola Parvovirus B19 Rash-associated enteroviruses

58
Q

Which RNA viruses are positive-stranded ssRNA?

A

+ssRNA ≈ mRNA and are infectious when purified

Retrovirus

Togavirus

Flavivirus

Coronavirus

Hepevirus

Calcicivirus

Picornavirus

“I went to a retro toga party where I drank flavored Corona and ate hippy California pickles”

59
Q

Yellow fever

A

Flavivirus

Enveloped, icosahedral, linear +ssRNA

Aedes aegypti mosquito bite (arbovirus)

High fever, black vomit, jaundice

Live attenuated vaccine

60
Q

What respiratory infections are associated with AIDS?

A

CMV pneumonia Aspergilllosis Pneumocystis peumonia –> Pneumocystis jirovecii Pneumonia –> S. pneumoniae TB-like disease –> Mycobacterium avium-intracellulare (Mycobacterium avium complex [MAC])

61
Q

What respiratory infections are associated with AIDS?

A

CMV pneumonia Aspergilllosis Pneumocystis peumonia –> Pneumocystis jirovecii Pneumonia –> S. pneumoniae TB-like disease –> Mycobacterium avium-intracellulare (Mycobacterium avium complex [MAC])

62
Q

What are dermatologic infections associated with AIDS?

A

Candidiasis of mouth, esophagus Hairy leukoplakia on lateral tongue –> EBV Bacillary angiomatosis –> Bartonella henselae

63
Q

What are neurologic infections associated with AIDS?

A

Ring-enhancing lesions –> Toxoplasma gondii Dementia Encephalopathy –> JC virus reactivation Meningitis –> cryptococcus neoformans Retinitis –> CMV (cotton-wool spots)

64
Q

What are oncologic disease associated with AIDS?

A

Non-Hodgkin lymphoma –> EBV Primary CNS lymphoma –> EBV Squamous cell carcinoma of rectum or cervix –> HPV Kaposi sarcoma –> HHV-8

65
Q

What CSF findings are consistent with viral meningitis?

A

Normal/↑ opeing pressure

↑ lymphocytes

Normal/↑ protein

Normal glucose

USMLE Step 1 (20 decks)

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