Virology Flashcards
Recombination
Exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology
Reassortment
When viruses with segmented genomes exchange segments
High-frequency recombination
Cause of worldwide influenza pandemics
Complementation
When 1 of 2 viruses that infect the cell has a mutation that results in a nonfunctional protein
The non-mutated virus “complements” the mutated one by making a functional protein that serves both viruses
Phenotypic Mixing
Occurs with simultaneous infection of a cell with 2 viruses
Genome of virus A can be partially or completed coated with the surface proteins of virus B
Type B protein coat determines the tropism (infectivity) and the progeny will be type A genetic material
The only ssDNA virus
Parvoviridae (Parvovirus)
The only dsRNA virus
Reovirus
Naked Viral Genome Infectivity
Purified nucleic acids of most dsDNA (except poxviruses and HBV) and + strand ssRNA (mRNA) are infectious. Naked nucleic acids of - strand ssRNA and dsRNA viruses are not infectious and require polymerases contained in the complete viron
Viral Replication (nucleus or cytoplasm?)
All DNA viruses replicate in the nucleus (except poxvirus–has own DNA dependent RNA polymerase–so it doesn’t need host’s version to make mRNA)
All RNA viruses replicate in the cytoplasm (except influenza virus and retroviruses)
General DNA virus Characteristics
Double stranded (except parvo) Linear (except papilloma, polyoma, and hepadna) Icosahedral (except pox) Replicate in the nucleus (except pox)
Herpesvirus Envelope(?) and DNA structure
Enveloped
Linear dsDNA
HSV-1 Transmission, Presentation, and Latent Location
Transmitted by respiratory secretions and saliva
Causes oral (and some genital) lesions, spontaneous temporal lobe encephalitis, and keratoconjunctivitis
Latent in trigeminal ganglia
HSV-2 Transmission, Presentation, and Latent Location
Transmitted by sexual contanct or perinatally
Genital (and some oral) lesions (herpes genitalis)
Neonatal herpes
Latent in sacral ganglia
VZV (HHV-3) Transmission, Presentation, Latent Location, andComplication
Transmitted by respiratory secretions
Causes chickenpox, zoster (shingles), encephalitis, and pneumonia
Latent in dorsal root or trigemina ganglia
Can get post-herpetic neuralgia from singles
EBV (HHV-4) Transmission, Presentation, Diagnosis, and Complications
Transmitted by respiratory secretions and saliva
Causes mononucleosis (characterized by fever, hepatosplenomegaly, pharyngitis, and lymphadenopathy). Infects B cells (but on peripheral blood smear you see reactive T cells)
Detected by + monospot test (heterophile antibodies detected by agglutination of sheep or horse RBCs)
Associated with Hodgkin lymphoma, Burkitt lymphoma, and nasopharyngeal carcinoma
CMV (HHV-5) Transmission and Presentation
Transmitted congenitally and by transufsion, sexual contact, saliva, urine, transplant
Causes congenital infection, mononucleosis (-monospot), pneumonia, retinitis
Infected cells have characteristic “owl eye” inclusions
Latent in mononuclear cells
Causes problems mostly in immunocompromised patients
HHV-6 Transmission and Presentation
Transmitted by saliva
Causes roseola: high fevers for several days that can cause seizures, followed by a diffuse macular rash
HHV-7 can also cause roseola (less commonly)
HHV-8 Transmission and Presentation
Transmitted by sexual contact
Can cause kaposi sarcoma, a neoplasm of endothelial cells Seen in HIV/AIDS and transplant patients
You get dark/violaceous flat and nodular skin lesions representing endothelial growths
Can also affect GI tract and lungs
HHV-6 Transmission and Presentation
Transmitted by saliva. Causes roseola: high fevers for several days that can cause seizures, followed by a diffuse macular rash. HHV-7 can also cause roseola (less commonly)
HHV-8 Transmission and Presentation
Transmitted by sexual contact. Can cause kaposi sarcoma, a neoplasm of endothelial cells. Seen in HIV/AIDS and transplant patients. You get dark/violaceous flat and nodular skin lesions representing endothelial growths. Can also affect GI tract and lungs
HBV Family, Envelope (?) and DNA Structure
Hepadnavirus, enveloped, and circular dsDNA (partially ds)
HBV Presentation, Vaccine (?), and reverse transcriptase (?)
Can cause acute or chronic hepatitis. There is a vaccine available. It is not considered a retrovirus, but it does has reverse transcriptase (it has a DNA polymerase that has DNA and RNA dependent abilities)
Adenovirus Envelope (?), Structure, and Presentations
It has no envelope. It has linear dsDNA. It can cause febrile pharyngitis, acute hemorrhagic cystitis, pneumonia, and conjunctivitis (“pink eye”)
Parvovirus Envelope (?), Structure, and Presentations
It has no envelope, it has linear ssDNA (-). Parvovirus B19 can cause aplastic crises in sickle cell disease, “slapped cheeks” rash in children which is called erythema infectiosum (fifth disease), RBC destruction in fetus leads to hydrops fetalis and death. Pure RBC aplasia and rheumatoid arthritis-like symptoms in adults
Papillomavirus Envelope (?), Structure, and Presentations
No envelope. circular dsDNA. HPV can cause warts (1,2,6,11), CIN, and cervical cancer (16,18,31,33). Vaccine available
Polyomavirus Envelope (?) and Structure
No envelope. Circular dsDNA
Polyomavirus Presentations
JC virus can cause progressive multifocal leukoencephalopathy (PML) in HIV. The BK virus is seen in transplant patients and commonly targets the kidney. JC= junky cerebrum and BK=bad kidney
Poxvirus Envelope (?) and Structure
It has an envelope. Linear dsDNA. Only non-icosahedral DNA virus (complex)
Poxvirus Presentations
Smallpox (eradicated but could be used in warfare)
Cowpox (“milkmaid blisters”)
Molluscum contagiosum: flesh=colored dome lesions with central umbilicated dimple
HSV Identification
Viral culture for skin/genitalia. CSF PCR for herpes encephalitis. Tzanck test (smear of an opened skin vesicle to detect multinucleated giant cells) to detect genital herpes
Reovirus Envelope (?), Structure, and Medical Importance
No envelope, linear dsRNA, icosahedral. Coltivirus causes colorado tick fever (transmitted by ticks), and rotavirus is the number 1 cause of fatal diarrhea in children
Reovirus Envelope (?), Structure, and Presentation
No envelope, linear dsRNA, icosahedral. Coltivirus causes colorado tick fever (transmitted by ticks), and rotavirus is the number 1 cause of fatal diarrhea in children
Picornavirus Envelope (?), Structure, and Presentation
No envelope, linear +ssRNA, icosahedral. Examples include poliovirus (vaccine available), echovirus (aseptic meningitis), rhinovirus (common cold), coxsackievirus (aspetic meningitis, herpangina:mouth blisters and fever, hand/foot/mouth disease, mycoarditis, pericarditis), and hepatitis A virus. PERCH
Hepevirus Envelope (?), Structure, and Presentation
No envelope, linear +ssRNA, icosahedral. Hepatitis E virus is an example
Calicivirus Envelope (?), Structure, and Presentation
No envelope, linear +ssRNA, icosahedral. Norovirus is an example and causes gastroenteritis (diarrhea–usually in adults)
Flavivirus Envelope (?), Structure, and Presentation
Enveloped, linear +ssRNA, icosahedral. Some examples: hepatitis C, yellow fever, dengue, st. louis encephalitis, and west nile virus (the last 4 are arboviruses transmitted by arthropods)
Togavirus Envelope (?), Structure, and Presentation
Enveloped, linear +ssRNA, icosahedral. Causes rubella, eastern equine encephalitis, and western equine encephalitis (these two are arboviruses transmitted by arthropods)
Retrovirus Envelope (?), Structure, and Presentation
Enveloped, linear +ssRNA, icosahedral (HTLV) or complex and conical (HIV). Have reverse transcriptase.
Retrovirus Envelope (?), Structure, and Presentation
Enveloped, linear +ssRNA, icosahedral (HTLV) or complex and conical (HIV). Have reverse transcriptase. HTLV can cause T-cell leukemia, and HIV causes AIDS
Coronavirus Envelope (?), Structure, and Presentation
Enveloped, linear +ssRNA, helical. Can cause the common cold but also SARS
Orthomyxovirus Envelope (?), Structure, and Presentation
Enveloped, linear -ssRNA, helical. Example: influenza virus
Paramyxovirus Envelope (?), Structure, and Presentation
Enveloped linear -ssRNA, helical. Examples: parainfluenza (croup), RSV (bronchiolitis in babies, treat with ribavirin), measles, mumps. PaRaMyxovirus.
Reovirus Envelope (?), Structure, and Presentation
No envelope, linear dsRNA, icosahedral. Segmented with 10-12 segments. Coltivirus causes colorado tick fever (transmitted by ticks), and rotavirus is the number 1 cause of fatal diarrhea in children
Orthomyxovirus Envelope (?), Structure, and Presentation
Enveloped, linear -ssRNA, helical. Segmented with 8 segments. Example: influenza virus
Paramyxovirus Envelope (?), Structure, and Presentation
Enveloped linear -ssRNA, helical. Examples: parainfluenza (croup), RSV (bronchiolitis in babies, treat with ribavirin), measles, mumps. PaRaMyxovirus
Rhabdovirus Envelope (?), Structure, and Presentation
Enveloped, -ssRNA, helical. Rabies is an example
Filovirus Envelope (?), Structure, and Presentation
Enveloped, -ssRNA, helical. Ebola/Marburg hemorrhagic fever–often fatal
Arenavirus Envelope (?), Structure, and Presentation
Enveloped, -ssRNA, helical. Segmented with 2 segments. Examples: lymphoytic choriomeninitis virus (LCMV) and lassa fever encephalitis (spread by mice)
Bunyavirus Envelope (?), Structure, and Presentation
Enveloped, -ssRNA, helical. Segmented with 3 segments. Examples: california encephalitis, sandfly/rift valley fevers, crimean-congo hemorrhagic fever, and hantavirus (hemorrhagic fever, pneumonia). the first 3 are arboviruses
Bunyavirus Envelope (?), Structure, and Presentation
Enveloped, -ssRNA, helical. Segmented with 3 segments. Examples: california encephalitis, sandfly/rift valley fevers, crimean-congo hemorrhagic fever, and hantavirus (hemorrhagic fever, pneumonia). the first 3 are arboviruses
Negative-stranded RNA Viruses Necessity
Must transcribe - to +. Therefore it brings its own RNA-dependent RNA polymerase
Segmented Viruses
All are RNA viruses. BOAR (bunyaviruses, orthomyxoviruses, arenaviruses, reoviruses)
Picornavirus Mechanism and Other Info
PERCH (poliovirus, echovirus, rhinovirus, coxsackievirus, HAV). RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins. Can cause aseptic (viral) meningitis (except rhinovirus and HAV). All are enteroviruses (fecal/oral spread) except rhinovirus (doesn’t infect the GI tract bc it’s acid-labile
Picornavirus Mechanism and Other Info
PERCH (poliovirus, echovirus, rhinovirus, coxsackievirus, HAV). RNA is translated into 1 large polypeptide that is cleaved by proteases into functional viral proteins. Can cause aseptic (viral) meningitis (except rhinovirus and HAV). All are enteroviruses (fecal/oral spread) except rhinovirus (doesn’t infect the GI tract bc it’s acid-labile
Yellow Fever Virus Family, Transmission, and Symptoms
It’s a flavivirus (also an arbovirus) transmitted by Aedes mosquitoes. It has a monkey or human reservoir. Symptoms are high fever, BLCK vomitus, and jaundice (flavi=yellow/jaundice)
Rotavirus Family and Disease
It is a reovirus. It is the most important global cause of infantile gastroenteritis. It is a major cause of acute diarrhea in the US during winter, especially in day-care centers and kindergartens. Villous destruction with atrophy. Vaccine available and recommended for all infants
Rotavirus Family and Disease
It is a reovirus. It is the most important global cause of infantile gastroenteritis. It is a major cause of acute diarrhea in the US during winter, especially in day-care centers and kindergartens. Villous destruction with atrophy. Vaccine available and recommended for all infants
Influenza Virus Two Important Molecules and Complications
Contains hemagglutinin (promotes viral entry) and neuraminidase (promotes progeny virion release) antigens. Patients at risk for fatal bacterial superinfection. Genetic drift causes epidemics, but genetic shift causes pandemics
Influenza Virus Two Important Molecules and Complications
Contains hemagglutinin (promotes viral entry) and neuraminidase (promotes progeny virion release) antigens. Patients at risk for fatal bacterial superinfection. Genetic drift causes epidemics, but genetic shift causes pandemics
Rubella Virus Information
It’s a togavirus. It causes rubella which is fever, lymphadenopathy, arthralgias, and fine rash which starts on face and spreads . Mild disease in children but serious congenital disease (a ToRCHeS infection). Congenital findings include “blueberry muffin” apperance along with the triad of cataracts, deafness, and PDA
Paramyxovirus Basic Information
These include parainfluenza, RSV, measles, and mumps. They cause disease in children. All contain surface F (fusion) protein which causes respiratory epithelial cells to fuse. Palivizumab is an MAB against F protein and prevents pneumonia caused by RSV infection in premature infants
Measles Virus Presentation
3 Cs: cough, coryza, conjunctivitis. Koplik spots (red/white spots on buccal mucosa that precede the rash by 1-2 days) and descending maculopapular rash are characteristic.
Measles Virus Presentation
3 Cs: cough, coryza, conjunctivitis. Koplik spots (red/white spots on buccal mucosa that precede the rash by 1-2 days) and descending maculopapular rash are characteristic. Possible sequelae are encephalitis, giant cell pneumonia (in immunosuppressed) and subaute sclerosing panencphalitis years later. Vitamin A can be used to prevent severe exfoliative dermatitis in malnourished children
Measles Virus Presentation
3 Cs: cough, coryza, conjunctivitis. Koplik spots (red/white spots on buccal mucosa that precede the rash by 1-2 days) and descending maculopapular rash are characteristic. Possible sequelae are encephalitis, giant cell pneumonia (in immunosuppressed) and subaute sclerosing panencphalitis years later. Vitamin A can be used to prevent severe exfoliative dermatitis in malnourished children
Mumps Virus Presentation
You get parotitis, orchitis, and aseptic meningitis. Can cause sterility (especially after puberty).
Rabies Virus Information
Rhabdovirus. Bullet-shaped. Commonly found in purkinje cells of cerebellum and in hippocampal neurons. Long incubation period (travels to CNS by migrating in a retrograde fashion). Postexposure treatment is wound cleansing and vaccination +/- rabies immune globulin. Progression: fever/malaise leads to agitation/photophobia/hydrophobia leads to paralysis/coma leads to death. From bat, raccoon, skunk, and dog bites.
Hepatitis Signs and Symptoms
All Hepatitis: fever, jaundice, increased ALT and AST
Hepatitis A Virus Presentation
Fecal-oral transmission (the vowels hit your bowels: a and e). Usually asymptomatic but can cause mild acute hepatitis
Hepatitis E virus Presentation
Fecal-oral transmission (especially with waterborne epidemics). High mortality in pregnant women.
Hepatitis A Virus Transmission and Presentation
Fecal-oral transmission (the vowels hit your bowels: a and e). Usually asymptomatic but can cause mild acute hepatitis
Hepatitis E Virus Transmission and Presentation
Fecal-oral transmission (especially with waterborne epidemics). High mortality in pregnant women
Hepatitis B Virus Transmission and Presentation
Parenteral, sexual, or maternal-fetal transmission. Usually acute hepatitis but can cause chronic hepatitis in the young/immunosuppressed. Integrates into host genome and acts as an oncogene thus increasing HCC risk
Hepatits C Virus Transmission and Presentation
Transmitted mostly via blood. Generally chronic. Higher risk of HCC
Hepatits C Virus Transmission and Presentation
Transmitted mostly via blood. Generally chronic. Higher risk of HCC
Hepatitis D Virus Transmission and Presentation
Transmitted parenterally, sexually, or maternal-fetal (same as Hep B). Can only infect if Hep B is present. Can cause superinfection (infection after Hep B) or coinfection (longer course). Superinfection is bad for prognosis
Hepatitis A Serologic Markers
Anti-HAV IgM indicates active Hep A and Anti-HAV IgG indicates prior HAV infection and/or prior vaccination. It also protects against reinfection
Hepatitis B Serologic Markers
HBsAg: Surface antigen; indicates hepatitis B infection. Anti-HBs: antibody to surface antigen; indicates immunity to hep B. HBcAg: core antigen. Anti-HBc: antibody to core antigen; IgM=acute/recent infection and IgG=prior exposure OR chronic infection; positive during window period.
Hepatitis B Serologic Markers
HBsAg: Surface antigen; indicates hepatitis B infection. Anti-HBs: antibody to surface antigen; indicates immunity to hep B. HBcAg: core antigen. Anti-HBc: antibody to core antigen; IgM=acute/recent infection and IgG=prior exposure OR chronic infection; positive during window period. HBeAg: envelope antigen; indicates replication/transmissibility. Anti-HBe: antibody to HBeAg; indicates low transmissibility
Hepatitis B Serologic Markers
HBsAg: Surface antigen; indicates hepatitis B infection. Anti-HBs: antibody to surface antigen; indicates immunity to hep B. HBcAg: core antigen. Anti-HBc: antibody to core antigen; IgM=acute/recent infection and IgG=prior exposure OR chronic infection; positive during window period. Not present if immunized. HBeAg: envelope antigen; indicates replication/transmissibility. Anti-HBe: antibody to HBeAg; indicates low transmissibility; not present if immunized
HIV Genome and 3 Structural Genes
Diploid genome (2 molecules of RNA). Structural genes: env: gp120 is for attachment to host CD4+ T cell and gp41 is for fusion and entry. Gag is the capsid protein. Pol is the reverse transcriptase/protease/integrase
HIV Co-Receptors
Virus binds CCR5 (early) or CXCR4 (late) co-receptor and CD4 on T cells. However, it binds CCR5 and CD4 on macrophages. Thus if you have a homozygous CCR5 mutation you have immunity (heterozygous is a slower course)
HIV Co-Receptors
Virus binds CCR5 (early) or CXCR4 (late) co-receptor and CD4 on T cells. However, it binds CCR5 and CD4 on macrophages. Thus if you have a homozygous CCR5 mutation you have immunity (heterozygous is a slower course)
HIV Diagnosis
Diagnosis made with ELISA (sensitive test). Results confirmed with Western blot (specific). HIV PCR/viral load tests determine the amount of viral RNA in the plasma. Progression observed via CD4+ cell count
HIV Diagnosis
Diagnosis made with ELISA (sensitive test). Results confirmed with Western blot (specific). HIV PCR/viral load tests determine the amount of viral RNA in the plasma. Progression observed via CD4+ cell count (
HIV Stages of Infection
Flu-like (acute), feeling fine (latent), falling count, final crisis
HIV Stages of Infection
Flu-like (acute), feeling fine (latent), falling count, final crisis
