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Harvard Medical School 1st year > Viruses > Flashcards

Viruses Flashcards

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USMLE® Step 1 flashcards
1
Q

Epstein-Bar Virus

15 things

A

Category = DNA virus

  1. DNA virus (replicates in nucleus)
  2. Spread by saliva
  3. Fever
  4. Tender lymphadenopathy
  5. Pharyngitis and tonsillar exudates
  6. Reactive cytotoxic CD8+ T cells present in blood smear
  7. Splenomegaly
  8. Latent in B cells
  9. Maculopapular rash (if mistakenly given amoxicillin)
  10. Hodgkin’s lymphoma
  11. Burkitt’s lymphoma
  12. Nasopharyngeal carcinoma
  13. Diagnose w/ monospot test
  14. Treat by telling patients not to do contact sports that will rupture their enlarged spleen.
  15. Gammaherpes subfamily
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2
Q

Poliovirus

9 things

A

Category = RNA virus (intro to virology section)

  1. Positive strand
  2. RNA virus
  3. Picornavirus family
  4. Enters thru GI tract then replicates in Peyer’s patches for 2-3 weeks
  5. Affects anterior horn of spinal cord (motor neurons)
  6. Asymmetrical paralysis
  7. Aseptic meningitis
  8. Salk’s vaccine = killed vaccine, parental injection, three serotypes
  9. Sabin’s live attenuated vaccine = oral, IgA antibodies to protect gut, but can cause spread via fecal-oral route.
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3
Q

Varicella-Zoster Virus

20 things

A

Category = DNA viruses

  1. Herpes virus
  2. Encapsulated (like all herpes viruses)
  3. Chicken pox
  4. Fever
  5. Headache
  6. Transmitted by respiratory droplets
  7. Vesicular “dew drops on rose petals” lesions/rash
  8. Lesions always present in different stages of healing
  9. Live attenuated virus available for children.
  10. Affect immunocompromised adults: encephalitis, pneumonia.
  11. Treat with Acyclovir for 12+
  12. Dorment in dorsal root ganglion
  13. Reactivated in immunocompromised, aging, stress.
  14. Reactivated form = shingles
  15. Vesicular rash that’s very painful; if crosses midline, then it has disseminated and is sign of immunocompromise (HIV)
  16. Postherpetic neuralgia = pain after rash goes away
  17. Herpes zoster opthalmicus = vision impairment if V1 nerve is infected
  18. Treat shingles with acyclovir, famcyclovir, varcyclovir
  19. Live-attenuated virus for 60+ available.
  20. Congenital varicella syndrome = limb hypoplasia, cutaneous dermatome scarring, and blindness.
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4
Q

Notes about DNA viruses (4)

A
  1. DNA viruses replicate their nucleic acids into capsids inside the host’s nucleus.
  2. DNA viruses use host’s DNA-dependent RNA polymerase to synthesize their mRNA
  3. Cause persistent (latent or chronic) infections.
  4. Some persistent infections cause cancer.
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5
Q

Hepatitis A

14 things

A

Category = Disseminated RNA virus

  1. Positive sense RNA: serves as template to negative sense RNA that further transcribes to positive sense RNA
  2. Acid stable
  3. Naked (no envelope) virus
  4. Fecal-oral
  5. Causes liver disease (hepatitis/hepalomegaly)
  6. Spread thru contaminated water in endemic areas
  7. Spread thru contaminated shellfish in developed countries.
  8. Causes jaundice in adults
  9. Anicteric (no jaundice) hepatitis in children and infants.
  10. Causes aversion to smoking in smokers
  11. Symptoms last for one month
  12. Vaccine = inactivated form of virus.
  13. Detect using ELISA for IgM-HAV antibodies.
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6
Q

West Nile Virus (flavivirus)

11 things

A

Category = Disseminated RNA virus (disseminated to nervous system)

  1. positive sense RNA
  2. Enveloped virus
  3. inside birds
  4. vectors = mosquitos
    - not spread via feces
  5. encephalitis and myelitis (tropism for neurons)
  6. meningitis
  7. flaccid paralysis
  8. seizures
  9. coma
  10. detection by serology
  11. no treatment
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7
Q

Structure of Fungus

4 things

A
  • eukaryotic, so all the same organelles of animal cell
  • ergosterols which are polysaccharides that are long chains and crosslink to form cell wall.
  • 1,3 B-D glucan which are like cholesterol and provide stability to cell membrane.
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8
Q

Antifungal drugs (4)

A
  1. Flucytosine = inhibit DNA and RNA synthesis with 5-FU
    - adverse effect = suppress hematopoiesis
  2. Polyene (Amphotericin B) = disrupt the ergosterols, make pores that allow ion flux to kill fungal cell.
    - adverse effect = toxicity, nephrotoxicity.
  3. Azole (Itraconazole) = disrupts synthesis of ergosterols by binding and inhibiting 14-alpha-demethylase that catalyzes synthesis of ergosterols.
    - adverse effect = inhibits P450 enzyme, blocks metabolism of other drugs.
  4. Echinocandin = disrupts synthesis of 1,3 B-D glucan.
    - adverse effect = mild.
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9
Q

Histoplasma capsulatum

A

Category = Fungus

  1. ohio river and mississippi valley of US
  2. mild manifestations = fever, dyspnea, cough
  3. Severe manifestations = acute cavitary disease (cavity in the lung), disseminated infection.
  4. Risk factors = immunocompromised, transplant recipient on constant immunosuppressants, HIV with low CD4, young female.
  5. Diagnose with serology (culture really slow); urine antigen test.
  6. Immune response is Th1-helper cell activates macrophages that phagocytose fungus.
  7. Transmission by inhalation of mold (spore/canidia); cannot be transmitted as yeast.
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10
Q

Blastomycosis Dermatitidis

A

Category = Fungus

  1. east of ohio river, mississippi valley of US
  2. mild manifestations = fever, dyspnea, cough
  3. Severe manifestations = cavitary disease
  4. Risk factors = again, immunocompromised
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11
Q

Coccidiomycosis Immitis

A

Category = Fungus

  1. southwest (california) of US
  2. mild manifestations = fever, dyspnea, cough
  3. severe manifestations = acute cavitary disease, dissemination.
  4. risk factors = immunocompromised, filipino/south african.
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12
Q

Retrovirus (HIV)

21 things

A

Category = Disseminating RNA Virus

  1. Positive sense, RNA virus
  2. Enveloped
  3. Diploid RNA found in capsid
  4. gag = p24 protein for capsule
  5. env = gp41 and gp120; transmembrane protein and outer glycoprotein of envelope respectively.
  6. pol = reverse transcriptase
  7. torch infection(vertical transmission)
  8. initially affects macrophages
  9. CD4+ cells are affected
  10. primary infection/prodrome = flu and mono-like symptoms
  11. lymphadenopathy
  12. fever
  13. Latent for 10 years
  14. Reactivated with CD4 < 200 count
  15. causes B-cell lymphomas
  16. entry via CCR5 receptor on CD4 T cells
  17. later entry via CXCR4 receptor of CD4 T cells
  18. Diagnose with Elisa (screening)
  19. Immuno/western blot for confirmation
  20. Neonates can have antibodies but perhaps not DNA (so can’t just use ELISA/immunoblot to test. Test DNA/RNA).
  21. Treatment with…
    - nRTIs (nucleotide reverse transcriptase inhibitor) which are backbone of antiviral therapy.
    - nnRTIS (non nucleotide reverse transcriptase inhibitor) which basically prevents activity of virus’s RT to make DNA from RNA.
  22. protease inhibitor (dauronavir)
  23. Maraviroc = CCR5 inhibitor.
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13
Q

Rotavirus (type of reovirus)

11 things

A

Category = Double stranded RNA virus, Mucosal RNA Virus

  1. RNA, but double stranded.
  2. 11 segments in the virus
  3. naked virus
  4. fecal-oral spread
  5. causes watery diarrhea
  6. NSP4 toxin causes chloride permeability and secretory diarrhea
  7. occurs in infants and children (number one reason for severe diarrhea)
  8. occurs in wintertime
  9. treat with oral rehydration
  10. vaccine with live attenuated virus, given orally.
  11. virus can cause intussusception.
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14
Q

Norovirus (Calisivirus)

5 things

A

Category = Mucosal RNA Virus

  1. Positive sense RNA virus
  2. Naked
  3. Makes one, long polyprotein that needs to be cleaved by viral proteases
  4. affects…
    - people on cruise ships
    - children (esp. in daycare)
    - people eating shellfish or other foods touched by infected ppl.
  5. causes explosive watery diarrhea.
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15
Q

Influenza (Orthomyxovirus)

15 things

A

Category = mucosal virus (respiratory tract mucosa)

  1. Negative sense RNA
  2. Replicated in Nucleus (only virus that doesn’t replicate in cytoplasm)
  3. Enveloped
  4. 8 segments
  5. Antigenic drift = point mutations that cause seasonal flu/epidemics
  6. Antigenic shift = reassortment of viral segments that makes new species of virus, causes pandemics.
  7. Hemagluttinin = glycoprotein on virus’s cell surface, allows binding to sialic acid of URT cells and RBC; upon binding virus gets endocytosed.
  8. M2 ion channel = shuttles protons into the virus, allowing uncoating of RNP (ribonucleoprotein).
  9. Amantadine = antiviral drug that inhibits M2 ion channel, inhibits uncoating. ONLY WORKS ON INFLUENZA A.
  10. Neuraminidase = cleaves sialic acid to release new viral particles.
  11. Neuraminidase inhibitor = Tamiflu, inhibits budding/release of viral particles. WORKS ON BOTH INFLUENZA A and B.
  12. Killed IM vaccine
  13. Live attenuated Nasal vaccine.
  14. Severe manifestation = pneumonia caused by staph aureas.
  15. If given aspirin, can develop Reyes syndrome, liver problems, and encephalitis.
    * *From class:
    - Damage host by damaging epithelial cells/cilia on epithelia cells and preventing host mRNA transcription and translation (protein synthesis is blocked).
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16
Q

Malaria (Plasmodium falciparum)

7 things

A

Category = parasites

  1. Maria symptoms are fever, headaches, anemia, splenomegaly.
  2. Detect by blood stain and Giemsa stain in RBCs.
  3. Banana shaped in blood smear
  4. Parasite goes thru antigenic variation to avoid host immune response.
  5. Plasmodium attaches to RBCs via knob-like projections, causes it to stick to endothelial walls, creating blockage of capillary beds; also prevents RBCs from being cleared out by the spleen.
  6. Transmission and Life cycle = anapholes mosquitos transmit sporozoites to human, sporozoites travel to liver to mature into trophozoites, they become schizonts that divide into merozoites and ruptures hepatocytes and releases to infect RBCs (in which merozoites mature into trophozoites > schizontes that rupture and infect more RBCs). Some merozoites go thru sexual reproduction to become gametozoites which can be taken up by mosquitos.
  7. Treatment with chloroquines = block plasmodium heme polymerase; another treatment is Artemisins/IV artesunate = for severe malaria.
17
Q

Babesia

10 things

A

Category = parasite

  1. has blood-related symptoms
  2. deer ticks transmit
  3. hemolytic anemia
  4. jaundice
  5. fevers (irregularly circulating fevers)
  6. diagnosed by blood smear (Maltese crosses on RBCs)
  7. prevalent in NE region of the U.S.
  8. severe disease if asplenic
  9. severe disease if has sickle cell disease
  10. treat with atovaquine and macrolide (azithromycin).
18
Q

Toxoplasmosis

11 things

A

Category = parasite (of CNS)

  1. transplacental transmission/torch infection
  2. transmitted by oocytes of cat feces
  3. cysts in raw and undercooked meat
  4. Immunocompromised people (esp. HIV) at risk.
  5. Encephalitis
  6. Enlarged rings in brain CT/ brain abscesses
  7. diagnose with brain biopsy/serology
  8. Four congenital symptoms =
    - intracranial calcifications
    - hydrocephalus > seizures
    - chorioretinitis
    - deafness
  9. treatment with sulfadiazine and pyrimethamine.
  10. CD4 <100 and serotest positive for IgG given prophylaxis.
  11. TMP-SMX prophylaxis (trimethoprim-sulfamethoxazole)
19
Q 
Giardia Intestiniasis (Lamblia)
(9 things)
A

Category = intestinal Protozoa

  1. common in campers and travelers
  2. transmitted as cysts
  3. transmit by unpurified water (can survive in CHLORINE - Swimming pool source of outbreak!!!).
  4. fecal-oral transmission
  5. foul smelling diarrhea
  6. steatorrhea = fatty stool
  7. trophozoites detected in stool O&P as diagnosis
  8. diagnose with ELISA stool antigen
  9. Treatment = metronidazole
20
Q

Amebiasis (Entamoeba Histolytica)

7 things

A

Category = intestinal Parasite

  1. transmitted by cysts
  2. transmitted by contaminated water (fecal-oral)
  3. Liver affected
    - abscess in right lobe
    - upper right quadrant pain
    - see abscess with CT
  4. Intestines affected
    - trophozoites infect intestines
    - flask-shaped lesions
    - ulcers
  5. Trophozoites engulf red blood cells
  6. Diagnose with stool O&P, serology, ELISA
  7. Treatment = metronidazole, paramycin
21
Q

Cryptosporidium

7 things

A
  1. causes severe diarrhea in HIV/immunocompromised patients.
  2. Acid-fast stain
  3. Infectious cysts in the stool
  4. Oocysts have 4 motile spores
  5. Sporozoites attach to wall of small intestines and cause watery diarrhea
  6. Treatment = nitazoxanide for healthy children.
  7. Filter oocysts out of water. Oocysts are NOT KILLED BY CHLORINE!!!
22
Q

Helminths
(Important things from lecture)

  • Where do helminths replicate? Which one is an exception?
  • Where do helminths mature? Where are they infectious?
  • What type of transmission not possible?
  • Who do these worms affect the most detrimentally and how?
  • For hookworms, who are most susceptible?
  • What other factors make individuals more susceptible to worms?
  • Which worm causes holes in brain and where does the infection occur most commonly?
A
  • helminths do not replicate in humans except strongyloides.
  • all helminths mature inside human, but infectious eggs are outside in the environment.
  • no direct person-to-person transmission
  • affects malnourished children most detrimentally.
  • for hookworms, women are more susceptible because they don’t have has much iron.
  • corticosteroids and immunocompromised make patients more susceptible to worms.
  • cysterocosis = makes holes in brain; pig-raising environment most common.
23
Q

Candida albicans

3 things from session slides

A

Category = opportunistic fungus

  1. dimorphic
  2. causes diaper rash (along with skin rash under large breasts)
  3. affects immunocompromised
  4. thrushes = white plaques in oral, esophagus, and vaginal mucosa.
  5. Risk factors = diabetes, antibiotics, birthcontrol, immunosuppressants (corticosteroids), HIV.
  6. treat with/ azoles for mild, amphotericin (polyene).
    * * from notes (remember this)
  7. Entry: on mucosal surfaces of all humans, transmitted person-person at early age.
  8. Risk factors: neutropenia, immunocomp/suppressed, intravenous catheters, burns and scars.
  9. Manifestations: superficial is thrush in oral, esophagus, vaginal mucosa, can cause diaper rash. Invasive is kidney and optic.
24
Q

Cryptococcus neoformans

  1. Infection acquired by…
  2. Avoids host immune by…
  3. Invasive infection causes…
  4. Spread is…
  5. Risk factors are…
  6. Diagnose with…
  7. Treat with…

from session slide:

  1. entry
  2. risk factors.
  3. manifestation.
  4. detection:
  5. special thing:
A

Category = opportunistic fungus

  1. inhalation into alveoli.
  2. capsule
  3. meningitis - headaches, fevers, cranial nerve palsies, mental status change.
  4. hematogenous to the CNS.
  5. AIDS, hematologic malignancies, transplant recipient, immunosuppressive drugs (corticosteroids)
  6. gram stain, india ink stain, latex agglutination antigen test, fungal culture.
  7. Flucytosine and amphotericin B (pyloene); then fluconazole for maintenance. CAN’T USE ECHINOCANDIN, NO 1,3 B-D GLUCAN.
    * * remember this from the session slides:
  8. entry: inhalation
  9. risk factors: immunocomp/suppressed; low T cells
  10. manifestations: neurotropism.
  11. detect by: latex agglutination, india ink stain, gram stain, culture.
  12. special thing: no 1,3 B-D glucan so can’t use echinocandin.
25
Q

Aspergillus
(7 things)

from session slides:

  1. entry
  2. risk factors
  3. manifestations (3 things, think “A” in Aspergillus)
A

Category = opportunistic fungus

  1. septate hyphae
  2. conidiospores inhaled from air
  3. causes infection in lung (lung balls)
  4. angioinvasive and causes hemorrhage and necrosis (target lesion)
  5. risk factors = neutropenia, neutropenic, immunosuppressed (corticosteroids), transplant recipient.
  6. Prevention = air filter
  7. Caused by construction/where soil can get turned up.
  • *remember from session slides:
    1. entry: inhalation of spores/conidia from construction
    2. risk factors: neutropenia (remember acute leukemia patients)
    3. manifestations: pulmonary aspergillus, ANGIOINVASION, fungus balls in lung cavities.
26
Q

Pneumocystis Jirovecci

  1. entry
  2. risk factor
  3. manifestation
  4. special thing/detection
A
  1. entry: inhalation
  2. risk factor: low T cell; immunocomp/suppressed
  3. manifestation: PROTEINOUS FLUID causing HYPOXIA
  4. special thing: can’t be detected by gram stain or culture; need to use PCR.

Harvard Medical School 1st year (2 decks)

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