Virology I & II Study Sheet

Comprehensive practice flashcards covering viral replication steps, classifications, prion diseases, viral pathogens, transmission routes, and vaccines based on MLT 209 Virology I & II notes.

Why are viruses characterized as obligate intracellular pathogens?

They cannot replicate without a host cell.

What are the three major components of a virus's structure?

The capsid (protein coat that protects the viral nucleic acid core), protein spikes, and matrix.

What occurs during the attachment or absorption step of the viral replication cycle?

The released virion attaches to a host cell or is absorbed through endocytosis after attachment to a receptor; if the host cell is a bacteria, the virus is a bacteriophage.

What happens during the penetration step of viral replication?

The virion penetrates the host cell and releases the viral genome across the plasma membrane through endocytosis or membrane fusion.

What occurs during the genome release step of viral replication?

The capsid degrades as the genome material is released into the host cell.

How do viruses replicate their genome and produce viral proteins inside a host cell?

Viral mRNA is transcribed, replicated into a viral genome, and translated into viral proteins; viruses utilize the host cell's ribosomes to transcribe their viral RNA or DNA into mRNA.

What occurs during the assembly step of the viral replication cycle?

The viral strands are assembled into new capsids, turning into mature virions.

How are virions released in the final stage of the viral replication cycle?

Virions burst out of the host cell, causing cell lysis, and are released to repeat the viral life cycle.

How does the replication of retroviruses like HIV differ from most viruses regarding host chromosomes?

While most viruses replicate without integrating into host chromosomes, retroviruses integrate their reverse-transcribed viral DNA directly and permanently into the host genome.

What is antigenic shift?

Drastic changes in the virus that result in new H (hemagglutinin) and N (neuraminidase) antigens.

What is antigenic drift, and how does it cause Influenza Viruses to infect seasonally?

Antigenic drift refers to RNA replication errors causing minor changes in antigenic structure and epitopes, leading Influenza Viruses to infect hosts seasonally (typically October through September).

What is the definition of a virion?

The entire virus particle outside of the host cell.

What is a prion, and how does it form?

An infectious protein particle formed when the physiological host cellular prion protein ($\text{PrP}^C$) undergoes a conformational conversion into an abnormal, insoluble, beta-sheet-rich isoform ($\text{PrP}^{Sc}$).

Which antiviral drugs are the drugs of choice for treating HSV-1, HSV-2, and Varicella-Zoster Virus?

Valacyclovir or Acyclovir.

How does shell vial culture differ from traditional cell culture in detecting cytopathic effects (CPE)?

Shell vial culture utilizes centrifugation after inoculation onto a coverslip inside a shell vial to speed viral attachment and produce CPE within a few days, whereas traditional bottle cell culture can take weeks to grow.

What serological and laboratory methods are used for virus identification?

PCR, EIA, and direct testing for IgM or IgG.

Which viruses are categorized as double-stranded DNA viruses under the mnemonic VVHACHEH?

Variola Virus, Varicella-Zoster Virus (VZV), Herpes Simplex Virus (HSP), Adenovirus, Cytomegalovirus (CMV), Human Papilloma Virus (HPV), Epstein-Barr Virus (EBV), and Hepatitis B (HBV).

Are there single-stranded DNA viruses that are clinically significant according to the classification table?

No

Which virus is listed as a double-stranded RNA virus, and what is its capsid morphology?

Rotavirus, which is a naked dsRNA virus.

What viruses are classified under single-stranded RNA using the mnemonic MEW GRIM PERCH H2?

Measles Virus (Rubeola), Ebola Virus, West Nile Virus (WNV), German Measles (Rubella), Respiratory Syncytial Virus (RSV), Influenza Virus, Mumps Virus, Poliovirus, Enterovirus, Rhinovirus, Coronavirus (CoV), Human Immunodeficiency Virus (HIV), Hepatitis A (HAV), and Hepatitis C (HCV).

What are three general clinical characteristics of prion diseases?

1. They cause transmissible spongiform encephalopathies (TSEs)

2. They are rapidly progressive and always fatal

3. They have no available treatments or vaccinations.

What is Bovine Spongiform Encephalopathy (BSE) commonly known as?

Mad Cow Disease.

What causes Variant Creutzfeldt-Jakob Disease (vCJD)?

Ingestion of BSE-contaminated bovine neural tissue from an animal.

What is Classic Creutzfeldt-Jakob Disease (CJD)?

A rapidly progressive neurodegenerative dementia in humans.

What is Kuru, and how was it historically transmitted?

A prion disease historically confined to indigenous people caused by the ingestion of a deceased relative's neural tissue.

What is Chronic Wasting Disease (CWD), and which animal species does it affect?

A transmissible spongiform encephalopathy affecting cervids (deer, elk, and moose) that unexpectedly kills them without evidence of predation or trauma.

What are the hallmark symptoms of Scrapie in sheep and goats?

Motor incoordination and pruritus (severe itching of the skin).

How do the clinical presentations of HSV-1 and HSV-2 differ?

HSV-1 typically produces cold sores around the mouth with no disseminated disease, whereas HSV-2 is normally sexually transmitted and can cause disseminated disease if untreated.

What severe disseminated complications can result from Herpes Simplex Virus infection (Name 3)?

HSV encephalitis, hepatitis, and/or central nervous system (CNS) effects.

How can Herpes Simplex Virus be transmitted to an infant during delivery, and how is this managed?

Through contact with active sores at the time of delivery; prevented by delivering via C-section.

What diseases are caused by Coronavirus (CoV) in humans and animals?

In humans, respiratory tract infections and the common cold; in animals, epizootic disease causing devastating respiratory and enteric distress.

What percentage of the adult population is infected with Cytomegalovirus (CMV), and are they usually symptomatic?

$50\%-80\%$ of the adult population is infected and, no, they are usually asymptomatic.

What severe developmental complications can congenital Cytomegalovirus (CMV) cause in babies?

Hearing loss and developmental disabilities.

Through what bodily fluids is Cytomegalovirus (CMV) transmitted (name 6)?

Saliva, tears, urine, stool, breast milk, or through sexual intercourse.

What conditions and demographic statistics are associated with Epstein-Barr Virus (EBV)?

Mononucleosis in teens and adults, latent infections linked to Burkitt's lymphoma, transplant recipient complications, and infection of $95\%$ of Americans aged $40$ (asymptomatic in children).

What two clinical diseases are caused by Varicella-Zoster Virus (VZV)?

Varicella (chickenpox) and Herpes zoster (shingles).

At what age is the shingles vaccine recommended?

Recommended for adults aged $50$ and older.

How is Varicella-Zoster Virus transmitted, and when is an infected person contagious?

Via inhalation of respiratory secretions, inhalation of aerosols from skin lesions, or transplacentally; highly contagious $1-2$ days before symptoms appear.

What conditions are caused by Human Papillomavirus (HPV)?

Papillomas (common warts), genital warts, and cervical cancer linked to genital warts.

What target age group is recommended to receive the Human Papillomavirus (HPV) vaccine?

Girls and boys ages $11-12$.

What clinical condition is caused by Rotavirus, and by what age must routine childhood vaccination be completed?

Gastroenteritis (diarrhea) in infants and children; vaccination must be completed by $8$ months of age.

What severe respiratory complications can arise from Influenza Virus infection?

Fatal viral pneumonia and complications such as secondary bacterial pneumonia.

What are the primary clinical signs and complications of Mumps Virus?

Swollen parotid glands (parotitis), encephalitis, permanent neurological damage, and death.

What severe complications are associated with Measles Virus infection (name 8)?

1. Permanent neurological damage

2. Kills of the immune system

3. Death

4. Diarrhea

5. Otitis media

6. Bronchitis

7. Pneumonia

8. Encephalitis

What serious condition can German Measles (Rubella) cause via transplacental infection?

Congenital Rubella Syndrome

What percentage of pneumonia cases are caused by Adenovirus?

$10\%$ of pneumonia cases (it can also cause fatal acute respiratory disease).

Which specific adult groups are eligible to receive the Respiratory Syncytial Virus (RSV) vaccine?

Pregnant mothers, and individuals over age $50$ who are immunocompromised, around babies, or have Type 1 or insulin-dependent diabetes.

What is the primary vector for West Nile Virus (WNV), and who can be vaccinated?

Infected mosquitoes serve as the vector; a vaccine is available for dogs only, not humans.

How do Hepatitis A (HAV), Hepatitis B (HBV), and Hepatitis C (HCV) differ in transmission and vaccine availability?

HAV transmits via the fecal-oral route and has a vaccine; HBV and HCV transmit through blood-borne/sexual/maternal-neonatal routes, but only HBV has a vaccine (HCV does not).