Microparasitology - Virology

Vocabulary flashcards covering key terms, structures, families, and concepts from the virology lecture notes.

Virus

Smallest known infectious agent; non-living, sub-microscopic obligate intracellular parasite.

Virion

A complete, infectious viral particle composed of genome, capsid, and sometimes an envelope.

Capsid

Protein shell that protects the viral genome and provides structural symmetry.

Envelope

Host-derived lipid bilayer surrounding some virions; contains viral glycoproteins for attachment.

Genome

Viral nucleic acid (DNA or RNA, never both) carrying genetic information.

Obligate Intracellular Parasite

Organism that must enter a host cell to replicate; describes all viruses.

Sub-microscopic

Too small for light microscopy; requires electron microscopy for visualization.

Nucleocapsid

Genome plus structural proteins; the core of both naked and enveloped viruses.

Naked Virus

Virion consisting only of a nucleocapsid, lacking an envelope.

Enveloped Virus

Virion with nucleocapsid enclosed in a lipid membrane acquired from the host cell.

Glycoprotein Spikes

Envelope proteins used by viruses to attach to and fuse with host cells.

Icosahedral Symmetry

Capsid architecture of 20 triangular faces, typical of many DNA and RNA viruses.

Helical Symmetry

Capsid winds around the genome forming a rod-like structure; common in RNA viruses.

Complex Symmetry

Capsid structure not purely icosahedral or helical (e.g., poxvirus).

Arbovirus

Arthropod-borne virus transmitted by mosquitoes or ticks.

Tissue Tropism

Preference of a virus for specific tissues or organs (e.g., adenovirus for respiratory tract).

Host Range

Spectrum of species a virus can infect: animal, plant, or bacterium.

Segment

Separate piece of genomic nucleic acid in segmented RNA viruses.

Segmented Genome

Genome divided into multiple segments (e.g., Orthomyxoviridae: 8).

Unsegmented Genome

Genome present as a single continuous molecule.

ssDNA

Single-stranded DNA genome (e.g., Parvoviridae).

dsDNA

Double-stranded DNA genome (e.g., Herpesviridae).

ssRNA

Single-stranded RNA genome (majority of RNA viruses).

dsRNA

Double-stranded RNA genome (e.g., Reoviridae).

Linear Genome

Nucleic acid arranged end-to-end (e.g., Adenoviridae).

Circular Genome

Nucleic acid forms a closed loop (e.g., Papillomaviridae).

Capsid Functions

Protect genome, aid transmission, recognize target cells, package genetic material.

Envelope Functions

Mediates attachment, entry, and budding; sensitive to drying and detergents.

Cell Lysis

Destructive exit mechanism of naked viruses causing host cell rupture.

Budding

Exit of enveloped viruses through host membrane, acquiring envelope.

Attachment

Initial binding of virion to host cell receptor.

Penetration

Entry of virus or nucleocapsid into host cell after attachment.

Uncoating

Release of viral genome from capsid inside the host cell.

Macromolecular Synthesis

Production of viral mRNA, proteins, and genomes using host machinery.

Assembly

Self-organization of viral components into new virions.

Release

Exit of newly formed virions via lysis (naked) or budding (enveloped).

Virus Latency

Dormant state where viral genome persists without active replication (e.g., HSV in ganglia).

DNA Virus Families

Parvoviridae, Papillomaviridae, Adenoviridae, Hepadnaviridae, Herpesviridae, Poxviridae.

RNA Virus Families

Picornaviridae, Flaviviridae, Togaviridae, Orthomyxoviridae, Paramyxoviridae, Coronaviridae, Filoviridae, Retroviridae, Rhabdoviridae, etc.

Adenoviridae

dsDNA, naked icosahedral viruses; cause conjunctivitis, respiratory and GI infections.

Hepadnaviridae

Partially dsDNA enveloped viruses; include Hepatitis B virus (Dane particle).

Herpesviridae

Enveloped dsDNA viruses; include HSV, VZV, CMV, EBV; establish latency.

Parvoviridae

Smallest viruses; ssDNA, naked; human B19 causes erythema infectiosum and anemia.

Papillomaviridae

Naked dsDNA viruses causing warts; oncogenic types 16 & 18 linked to cervical cancer.

Poxviridae

Largest, brick-shaped dsDNA viruses with complex symmetry; include smallpox virus.

Picornaviridae

Naked ssRNA icosahedral viruses; include poliovirus, rhinovirus, hepatitis A.

Flaviviridae

Enveloped ssRNA icosahedral arboviruses; include dengue, yellow fever, HCV.

Orthomyxoviridae

Enveloped ssRNA segmented viruses; influenza A, B, C; subtyped by H and N proteins.

Paramyxoviridae

Large enveloped ssRNA helical viruses; measles, mumps, parainfluenza.

Retroviridae

Enveloped ssRNA viruses with reverse transcriptase; include HIV-1 and HIV-2.

Rhabdoviridae

Bullet-shaped enveloped ssRNA viruses; rabies virus is the prototype.

Coronaviridae

Enveloped ssRNA helical viruses with crown-like spikes; SARS-CoV-2 causes COVID-19.

Filoviridae

Filamentous enveloped ssRNA viruses; Ebola and Marburg cause hemorrhagic fever.

Arbovirus Examples

Dengue, yellow fever, West Nile—all transmitted by mosquitoes.

Hepatitis B Surface Antigen (HBsAg)

Envelope protein marker of active HBV infection; elicits protective antibodies.

Anti-HBs

Antibody against HBsAg; confers immunity, generated by infection or vaccination.

HIV

Human Immunodeficiency Virus; retrovirus that targets CD4 T cells, leading to AIDS.

CD4 T Cell

Helper lymphocyte expressing CD4 receptor; primary target of HIV infection.

AIDS

Acquired Immunodeficiency Syndrome; advanced stage of HIV with severe immunosuppression.

Rabies Virus

Neurotropic rhabdovirus transmitted via animal bites; nearly 100% fatal once symptoms appear.

Dane Particle

Complete infectious form of Hepatitis B virus seen under electron microscopy.

Vaccine

Biological preparation that induces protective immunity against a specific virus.

Antiretroviral Drugs

Medications that inhibit stages of HIV replication to suppress viral load.

RT-PCR

Laboratory test converting viral RNA to DNA for amplification and detection.

Opportunistic Infection

Disease caused by normally harmless microbes in immunocompromised hosts (e.g., AIDS).

Smallpox

Eradicated poxvirus disease once prevented by vaccination.

Dengue

Flavivirus infection transmitted by Aedes mosquitoes; causes fever and hemorrhagic disease.

Nasopharyngeal Swab

Specimen collected from upper respiratory tract, used for COVID-19 detection.

Hemagglutinin

Influenza surface glycoprotein mediating attachment; basis for H subtyping.

Neuraminidase

Influenza enzyme aiding viral release; basis for N subtyping.

Bullet-shaped Virus

Describes rhabdoviruses such as rabies.

Brick-shaped Virus

Describes poxviruses with complex symmetry.

Filterable Agent

Historical term for viruses able to pass through bacteriological filters.

Ultracentrifugation

Technique to measure and purify viruses based on size and density.

Nanometer Scale

Unit of measurement (10-9 m) used for viral sizes (10–300 nm).

Antigenemia

Presence of viral antigens in the bloodstream during acute infection.

Viremia

Presence of infectious virions in the bloodstream.

Glycoprotein

Protein with attached sugars; forms viral spikes important for host interaction.

Spike Proteins

Protruding viral glycoproteins that mediate attachment and entry into host cells.