USMLE (Fach) / Virology (Lektion)

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USMLE

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  • Reovirus Naked, dsRNA and linear- 10-12 segments Coltivirus – Colorado tick fever Rotavirus – #1 cause of fatal diarrhea in children. Less common due to vaccination.
  • Picornavirus Naked, ⊕ ssRNA, linear PERCHPoliovirus  – polio-Salk/Sabin vaccines – IPV/OPVEchovirus – aseptic meningitisRhinovirus – "common cold"Coxsackievirus – aseptic meningitis; herpangina (mouth ...
  • Hepevirus Naked, ⊕ single stranded and linear HEV
  • Caliciviruses Naked, ⊕ single-stranded and linear Norovirus – viral gastroenteritis with vomiting, watery diarrea.
  • Flavivirus Enveloped, ⊕ single-stranded and linear HCVYellow fevera – Liver, kidney, heart, and GI (black vomit) damageDenguea – Break bone fever (rash, muscle and joint pain), reinfection can result in ...
  • Togavirus Enveloped, ⊕ ssRNA and linear Rubella – German measles (erythematous rash begins on face, progresses to torso)Eastern and Western equine encephalitisaChikungunya virusa
  • Coronaviruses Enveloped, ⊕ single-stranded and linear "Common cold", SARS, MERS
  • Orthomyxoviruses Enveloped, Θ single-stranded and linear- 8 segments Influenza virus
  • Rhabdoviruses Enveloped, Θ single-stranded and linear Rabies
  • Filoviruses Enveloped, ⊝ ssRNA, linear, helical Ebola/Marburg hemorrhagic fever – often fatal
  • Bunyaviruses Enveloped, ⊝ single-stranded and circular RNA- 3 segments  California encephalitisaSandfly/Rift Valley feversaCrimean-Congo hemorrhagic feveraHantavirus – transmission by rodent excrement, hemorrhagic ...
  • Rhinovirus A picornavirus (naked, ⊕ ssRNA) - Cause of common cold- >100 serologic types- Acid labile – destroyed by stomach acid, therefore, does not infect the GI tract (unlike other picornaviruses)
  • Yellow fever virus A flavivirus (enveloped, ⊕ ssRNA)- Arbovirus, transmitted by Aedes mosquito- Reservoir: Monkeys- Endemic in South America and Sub-Saharan Africa Symptoms:1. High fever, headaches, chills, aching ...
  • Rotavirus A segmented dsRNA (reovirus). - Most important global cause of infantile gastroenteritis.- Major cause of acute diarrhea in the US during winter, especially in day care centers, kindergartens. - Villous ...
  • Influenza virus Orthomyxovirus (enveloped, ⊝ ssRNA with 8 segments)- Contain hemagglutinin (binds sialic acid and promotes viral entry)- Contain neuraminidase (promotes progeny virion release) - Patients at risk for ...
  • Rubella virus Togavirus (enveloped, ⊕ ssRNA) Causes rubella, once known as German 3-day measles. Presentation:- Low-grade fever- Postauricular and nuchal lymphadenopathy- Arthralgias- Fine, maculopapular, confluent ...
  • Paramyxoviruses Enveloped, ⊝ ssRNA, non-segmented Parainfluenza – croup (seal-like barking cough)Mumps, MeaslesRSV – bronchiolitis in babies - All contain surface F (fusion) protein, which causes respiratory ...
  • Croup (acute laryngotracheobronchitis) Caused by parainfluenza viruses, which are paramyxoviruses (enveloped, ⊝ ssRNA).- Peak incidence: 6 months to 3 years- Most common in fall and winter Virus membrane contains hemagglutinin (binds sialic ...
  • Measles (rubeola) virus Paramyxovirus (enveloped, ⊝ ssRNA) - Prodromal fever with cough, coryza (inflammation of nasal mucosal), conjunctivitis, light sensitivity- Eventually Koplik spots (bright red spots with blue-white ...
  • Mumps Paramyxovirus (enveloped, ⊝ ssRNA)- Uncommon due to effectiveness of MMR vaccine Symptoms:- Parotitis- Orchitis (inflammation of testes)- Aseptic meningitis- Pancreatitis- Can cause sterility 
  • Rabies virus Rhabdovirus (bullet-shapped virus, enveloped, ⊝ ssRNA, helical)- Infection more commonly from bat, raccoon, and skunk bites (US) and dogs (worldwide).- Aerosol transmission (eg, bat caves) also possible. ...
  • Prions - conversion of a α-helical protein termed prion protein (PrPc) to a β-pleated form (PrPsc), which is transmissible via CNS-related tissue (iatrogenic CJD) or food contaminated by BSE-infected animal ...
  • Poxvirus Enveloped, dsDNA and linear (largest DNA virus) - Smallpox eradicated world wide by use of the live-attenuated vaccine- Cowpox ("milkmaid blisters")- Molluscum contagiosum – flesh-colored papule with ...
  • Hepadnavirus Enveloped, partially dsDNA and circular HBV: - Acute or chronic hepatitis- Not a retrovirus but has reverse transcriptase
  • Adenovirus Naked, dsDNA and linear - Febrile pharyngitis – sore throat- Acute hemorrhagic cystitis – mostly boys age 5-15- Pneumonia- Conjunctivitis – "pink eye"- Gastroenteritis- Myocarditis Prevention: live, ...
  • Papillomavirus Naked, dsDNA and circular HPV – warts (serotypes 1, 2, 6, 11), CIN, cervical cancer (most commonly 16, 18)- Infects basal layer of the skin and mucous membranes- Malignancy may result: E6 and E7 inhibit ...
  • Parvovirus Naked, ssDNA and linear (smallest DNA virus)- Attaches to P antigen on RBCs B19 virus - Aplastic crisis in sickle cell disease- "Slapped cheek" rash in children (erythema infectiosum, or fifth disease)- ...
  • Polyomavirus Naked, dsDNA and circular - JC virus – progressive multifocal leukoencephalopathy (PML) in HIV- BK virus – transplant patients, commonly targets kidney. Occurs in ~5% of all kidney transplants patients. ...
  • Herpes simplex virus-1 Enveloped, DS and linear Route: Respiratory secretions, saliva - Gingivostomatitis- Keratoconjunctivitis- Herpes labialis- Herpetic whitlow on finger- Temperal lobe encephalitis- Esophagitis- Erythema ...
  • Herpes simplex virus-2 Enveloped, DS and linear Route: Sexual contact, perinatal - Herpes genitalis- Neonatal herpes - Viral meningitis more common with HSV-2 than with HSV-1. - Tzanck smear looks for multinucleated giant cells ...
  • Varicella-Zoster virus (HHV-3) Enveloped, DS and linear Route: Respiratory secretions - Varicella-zoster (chickenpox, shingles), encephalitis, pneumonia- Most common complication of shingles is post-herpetic neuralgia. - Latent in ...
  • Epstein-Barr virus (HHV-4) Enveloped, DS and linear Route: Respiratory secretions, saliva; aka "kissing disease" Mononucleosis – fever, hepatosplenomegaly, pharyngitis, lymphadenopathy (especially posterior cervical nodes). Avoid ...
  • Cytomegalovirus (HHV-5) Enveloped, DS and linear Route: Congenital transfusion, sexual contact, saliva, urine, transplant- Uses integrins to cause infection - Mononucleosis (⊝ Monospot) in immunocompetent patients- Infection ...
  • Human herpes viruses 6 and 7 Enveloped, DS and linear Route: Saliva Roseola infantum (exanthem subitum):- High fevers for several days- Can cause seizures- Followed by diffuse macular rash - HHV-7 – less common cause of roseola
  • Human herpesvirus 8 Enveloped, DS and linear Route: Sexual contactSite of latency: B cells, glandular epithelial cells Kaposi sarcoma (neoplasm of endothelial cells)- Seen in HIV/AIDS and transplant patients- Dark/violaceous ...
  • RNA viruses Reovirus (DS): Rotavirus - cause of fatal diarrhea in children Picornavirus- Poliovirus- Echovirus - aseptic meningitis- Rhinovirus - "common cold"- Coxsackievirus - aseptic meningitis; herpangina; hand, ...
  • Ebola virus Filovirus (enveloped, ⊝ ssRNA)- Transmission requires direct contact with bodily fluids, fomites (including dead bodies), bats or primates (apes/monkeys); high incidence of nosocomial infection.- Targets ...
  • Zika virus Flavivirus (enveloped, ⊕ single-stranded)- Transmitted by Aedes mosquito.- Sexual or vertical transmission possible.- Outbreaks more common in tropical and subtropical climates. Presentation:- Conjunctivitis- ...
  • Hepatitis serologic markers Anti-HAV (IgM) – Best test to detect acute hepatitis A.Anti-HAV (IgG) – Indicates prior HAV infection and/or prior vaccination; protects against reinfectino. HBsAg – Indicates HBV infection.Anti-HBs ...
  • HIV Diploid genome (2 molecules of RNA). 3 structural genes:- env (gp120 and gp41): envelope glycoproteins→ gp120 – attachment to CD4+ T cell→ gp41 – fusion and entry- gag (p24 and p17): capsid ...
  • HIV diagnosis Presumptive diagnosis made with HIV-1/2 Ag/Ab immunoassays. - These immunoassays detect viral p24 Ag capsid protein and IgG Abs to HIV-1/2. Very high sensitivity/specificity.- ⊕ tests are confirmed ...
  • Common diseases of HIV-positive adults CD4+ count <500mm3:- Candida albicans – oral thrush- EBV – oral hairy leukoplakia- HHV-8 – Kaposi sarcoma (lymphocytic inflammation)- HPV – squamous cell carcinoma, commonly of anus or cervix ...
  • Viral genetics Recombination: Exchange of genes between 2 chromosomes by crossing over within regions of base sequence homology. Reassortment: When viruses with segmented genomes (eg, influenza virus) exchange genetic ...
  • DNA virus characteristics Are HHAPPPy viruses: Hepadna, Herpes, Adeno, Pox, Parvo, Papilloma, Polyoma. All DNA viruses have dsDNA except Parvoviridae (ssDNA). All are linear except papilloma and polyoma (circular, supercoiled) ...
  • RNA virus characteristics All RNA viruses have ssRNA except Reoviridae (dsRNA). All replicate in the cytoplasm (except retrovirus and influenza virus). (+) stranded RNA viruses: I went to a retro (retrovirus) toga (togavirus) ...
  • Viral envelopes Generally, enveloped viruses acquire their envelopes from plasma membrane when they exit the cell. Exceptions include herpesviruses, which acquire their envelopes from nuclear membrane. Naked viruses ...
  • HSV identification - Viral culture for skin/genitalia - CSF PCR for herpes encephalitis - Tzanck test – a smear of an opened skin vesicle to detect multinucleated giant cells commonly seen in HSV-1, HSV-2, and VZV infection. ...
  • Receptors used by viruses CMV – Integrins (heparan sulfate) EBV – CD21 HIV – CD4, CXCR4, CCR5 Parvovirus B19 – P antigen on RBCs Rabies – Nicotinic AChR Rhinovirus – ICAM-1
  • Retroviruses Enveloped, ⊕ ssRNA- 2 copies- Have reverse transcriptase HTLV (icosahedral) – T-cell leukemiaHIV (complex and conical) – AIDS
  • Arenaviruses Enveloped, ⊕ and ⊝ single stranded and circular RNA- 2 segments LCMV – lymphocytic choriomeningitis virusLassa fever encephalitis – spread by rodents