Parasitology Virology basics

Pandemic

Epidemic over a wide geographic area, or even worldwide.

Antigenic Shift

Major changes that result in novel viral antigens

Antigenic Drift

Minor changes that occur continuously over time as the virus replicates

Epidemiology

The study of the occurrence and distribution of disease and factors that control presence or absence of disease.

Viremia

Presence of viruses in the bloodstream.

Herd Immunity

Immunity to an infectious agent in a high percentage of a given population of people that helps prevents spread of disease.

Diagnosis

What cannot be made based on clinical presentation due to the number of viruses?

Rhinitis

The viruses that causes this are adenovirus, rhinovirus, coronavirus, rubella virus, influenza virus, and herpes simplex virus.

Pharyngitis

The viruses that cause this are adenoviruses, cornaviruses, coxsackie viruses, epstein-barr virus, herpes simplex virus

Vesicles/Blister-like lesions

The viruses that cause this are herpes simplex virus, varicella-zoster virus, smallpox virus, and coxsackie viruses

Exanthem/Rash

The viruses that cause this are rubella, rubeola, coxsackie, and echoviruses

Adenovirus

The symptoms caused by this virus are pharyngitis, conjunctivitis, laryngitis, pneumonia, diarrhea, cystitis, and systemic infection.

antivrial drugs

Small number of these for treatment due to the volatility of viruses.

Vidarabine

Antiviral drug used for herpes viral encephalitis that cna reduce mortality from 80% to <30%

Therapeutic Ig

This is used in cases of HBV exposure

C-section

This is done to prevent an HSV infection of a newborn

Epidemic

More localized spread of an “old” organism.

Virions

Virus particles that gain entry to the body via mucous membranes

Obligate intracellular organism

The type of parasite a virus is, meaning it cannot live on its own.

Attachment (adsorption)

Penetration (Entry)

Uncoating (removal of capsid)

Synthesis (Production of nucleic acid)

Assembly (structural proteins are put together into viruses)

Release (Cell lysis and release new viruses)

Steps of the infectious cycle

Acute viral stage

Happens very quickly

Latent viral stage

No symptoms but the virus is still inside, potentially waiting to emerge later

Chronic viral stage

Persistent symptoms that can last for very long times

Nasopharyngeal swabs or washings

The type of specimen collection for RSV, influenza, and COVID

Feces

The type of specimen collection for Norovirus, rotavirus, and enterovirus

Vesicular fluid or swabs

The type of specimen collection for skin lesions for HSV, VZV, coxsackie

CSF

The type of specimen collection for enteroviruses (polio and arboviruses

Urine

The type of specimen collection for mumps, CMV, rubella

Blood

Can be collected only during the acute phase of the infection due to viruses remaining only for a short duration, from the portal of entry to the site of the target organ.

Commercial swabs

Consists of Virocult, viral culturettes, and culturettes

Transport media

The liquid that swabs should be placed in to move viruses. Also consists of antibiotics and protein to remove bacteria.

4C

The temperature for viruses to be stored in due to enveloped viruses being weak to freezing temperatures and room temperature.

Cytopathology

The examination of stained tissue or cells by light microscopy for the presence and location of cytologic changes such as inclusions, necrosis, “giant” cells, cytoplasmic modifications, vacuolization.

Electron microscopy

The method to identify viruses for those that cannot be cultured, such as HBV and rotaviruses.

Direct Fluorescent antibody (DFA)

Detects viral antigens

Indirect Fluorescent Antibody (IFA)

More sensitive in detecting viral antigens

Direct IF steps

Flood slide with labeled antibody reagent

• antibody specific to viral antigen will bind if virus is present in specimen

• Perform a rinse/wash procedure to remove unbound antibody

• Examine for fluorescence using fluorescent microscope

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Virus cell culture supplies

Viruses require suitable host cells, a cell culture media, and an incubator

1-4 weeks

The incubation period needed to incubate viruses.

Living Cells

The type of specimen needed for viruses to multiply, because they are strict, intracellular parasites.

Cytopathic Effect (CPE)

The effects of a virus on a cell, causing things like cell death (pyknosis/necrosis), multinucleated cells, and abnormal rounding or swelling of cells

Cytopathic effect rate

The HSV is rapid, why VZV and CMV are slow.

RMK, MRC-5, Hep-2, A-549

The types of cells used for culture of viruses

Shell Vial Cell Culture

The rapid modification of traditional viral cell culture, where it is stained with virus-specific fluorescent antibodies.

Speed

The advantage of Shell Vial Cell Culture

Separate vial must be set up for each virus

The disadvantage of Shell Vial Cell Culture

MALDI-TOF MS

Matrix-Assisted Laser Desorption Ionization - Time of Flight - Mass Spectrometry

Mass of DNA/RNA

The principal of MALDI-TOF MS where it measures this to determine the base sequence.

NAAT or Culture

These are used in conjunction with MALDI-TOF MS

MALDI-TOF

NAAT

Nucleic Acid Amplification Techniques/Testing

PCR

Polymerase Chain Reaction

RT-PCR

Reverse transcriptase PCR (for amplification of RNA)

NAAT Terminology

Probe, amplicon, hybridize, complementary, quantitative, qualitative, multiplex

Acute specimens

Type of specimen obtained at the onset of symptoms.

IgM, lasts a few weeks

The type of immunoglobulin found in an acute specimen, and how long it lasts for.

Convalescent specimen

Type of specimen obtained 2-4 weeks later

IgG, lasts months to years

The type of immunoglobulin found in convalescent specimens, and how long it lasts for

Serological diagnosis

Performed when a demonstration of a 4-fold rise in titer between acute and convalescent specimens.

Single detectable titer

This may be indicative of lingering antibodies from a past infection, or a successful vaccination