Virology Flashcards
What are the components of a Virion?
- Genome: DNA or RNA (Instructions to clone itself)
- Protein coat: Protection, Facilitates attachment, and Antigens
- May contain enzymes needed for transcription (e.g. polymerase)
- No energy source
- No metabolic processes
What are viral spikes or glycoproteins?
- Protein (or protein + glycogen) that are antigens
- Responsible for different viral serotypes (viral subcategories)
What is the difference between a naked and an enveloped virus?
- Enveloped has outer lipid bilayer
- Naked survive better in the environment (i.e. not as sensitive to heat, drying, alcohol, etc)
What is the difference between positive and negative stranded viral RNA?
- Positive stranded can immediately be translated into protein.
- Negative stranded must be transcribed into a positive RNA strand prior to being translated. Virus can have it own enzyme to transcribe negative stranded to positive stranded
What is unique about retroviruses?
Even though they are positive stranded RNA virus they cannot be immediately translated. They use virion reverse transcriptase to copy RNA to DNA, which is then incorporated into the host genome
What are the (+) RNA Naked viruses?
- Calici (Norwalk)
- Hep E
- Reov (Rotavirus) Double Stranded
- Picorna (Polio, Echo, Rhino, Cox, Hep A)
What are the (+) RNA Enveloped viruses?
- Corona (viral pharyngitis)
- Retro (HIV) Reverse- transcribed
- Flavi (Westnile, Hep. C, Dengue, Yellow fever)
- Toga (Rubella, Alpha, Rubi)
What are the (-) RNA enveloped viruses?
- Bunya
- Paramyxo (Mumps and Morbilli –> Measles)
- Orthomyxo (Influenza A, B, C)
- Rhabdo (Rabies)
What are the Naked DNA viruses?
- Parvo (B19 –> Fifths Disease) Single Stranded
- Adeno
- Papilloma
What are the Enveloped DNA viruses?
- Hepadna
- Herpos (Varicella + Herpes Zoster, Herp 6 or 7 –> Roseola)
- Pox (Small pox)
What is unique about DNA viruses?
- DNA must first be transcribed into RNA, then translated into proteins (They make mRNA using host RNA polymerase)
- Positive strand is read and transcribed into mRNA
What is unique about a Prion?
- Composed entirely of protein
- No DNA or RNA
- Disrupts neuron function by converting normal cells into –> B-pleated sheets
Describe Viral Transmission
1-Attachment to host cell: Virion surface proteins attach to receptor proteins on the cell surface
2-Penetration/Entry: Naked viruses engulfed by vesicle
Enveloped viruses undergo fusion
3-Uncoating to release the genome: Low vesicle pH uncoats virion. Rupture or fusion SEE PICTURE
4-Gene expression: Virus specific mRNA synthesis
Synthesis of viral proteins
5-Genome replication: DNA viruses replicate in the nucleus using host cell DNA-dependent RNA polymerase
Exception = poxviruses – cytoplasm
RNA viruses replicate in the cytoplasm
6-Assembly:
Viral nucleic acid packaged within capsid proteins
Rupture of cell membrane releasing assembled virions (usually naked viruses)
OR
Budding process (enveloped viruses)
What happens to host cells when they become infected with a virus?
- Death: Macromolecular synthesis inhibited
- Fusion of cells to form multinucleated cells: Due to cell membrane changes
- Malignant transformation: Unrestrained growth, Prolonged survival, Morphologic changes
- No effect
What are the stages of a viral infection?
- Incubation: Asymptomatic
- Prodromal: Non-specific symptoms
- Specific-illness: Characteristic symptoms and signs
- Recovery: Illness wanes
- Persistence (sometimes): Chronic carrier state, latent infection
List the Viral Infection Diagnostic procedures.
- Cell culture – presumptive diagnosis
- Definitive identification – uses known antibody with various tests
- Microscopic identification
- Serologic procedures
- Viral antigens
- Viral nucleic acids
Define Cell culture diagnosis.
Virus growth produces characteristic cytopathic effect (CPE)
Describe serologic procedures.
Antibody titer in acute-phase and convalescent-phase (10-14 days later) compared (4-fold higher = infected)
What are the different types of vaccination immunity
1) Active immunity
- Attenuated live virus – greater, longer lasting protection
- Killed virus
- Subunit vaccines – contain purified viral proteins
2) Passive immunity
- Preformed antibody administered in immune globulins
3) Herd immunity – “community immunity”
What are some challenges that arise with viral disease control?
- Difficult to obtain selective toxicity against the virus since replication so closely involved with normal synthetic processes of the cell
- Extensive viral replication occurs during the incubation period
- Drug-resistant viral mutants
What are the respiratory illnesses?
- Common cold (Rhinoviruses)
- Viral pharyngitis
- Influenza
Common Cold Infectious agent…
- Rhinoviruses (30-50% case): Picornavirus family
- Naked (+) RNA
Common Cold transmission…
- Hosts: humans and chimps
- Entry point: URT
- Droplets (direct & indirect)
- Peaks: early fall or spring
Common Cold Signs/symptoms…
- Incubation: 2-4 days
- Duration: 1 week
- sneezing, nasal discharge, sore throat, cough, headache
Viral pharyngitis infectious agents…
Multiple!!… Coronavirus
Viral pharyngitis signs and symptoms…
- Headache, malaise, +/- fever, sore throat
- Nasal congestion, coryza, hoarseness, sinus discomfort/tenderness, ear pain, cough
Influenza infectious agents…
- Influenza A, B, C: Orthomyxovirus family
- Enveloped (–) RNA
- 2 glycoproteins
- Hemagglutinin (H1, H2, H3)
- Neuraminidase (N1, N2)
Describe antigenic shift vs drift
Drift: mutations
Shift: animal –> human… causes re-assortment of genome segments (big change!!) (H1N1)
Influenza transmission…
- Host: Humans
- Influenza A: mammals and birds
- Influenza B: seals
- Influenza C: pigs, dogs
- Entry point: respiratory tract
- Direct droplet spread
- Peak: winter months
Influenza signs and symptoms…
- Incubation: 2 days
- Duration: acute phase 3-5 days. Normal in 2-6 weeks
- Abrupt onset: FACTS
- F - fever
- A - aches (aka myalgias)
- C - chills
- T - tiredness
- S - sudden onset
- 6-12 hrs later respiratory signs (dry, nonproductive cough)
Influenza prevention…
Antivirals
- Neuraminidase inhibitors: block the enzyme so it can’t release/spread/infect
- Viral protein M2 inhibitor: block uncoating/assembly
Vaccines
- Killed (inactivated): virions/split subunits made of hemagglutinin antigens
- Live attenuated: antibodies form 2 weeks after vaccination
Influenza complications…
- Pneumonia
- Bacterial superinfection
- Reye’s syndrome
What are the Exanthem viruses?
- Varicella (Chickenpox)
- Herpes zoster (Shingles)
- Measles
- Roseola
- Rubella
- Fifth disease
Varicella (Chickenpox) infectious agents…
- Varicella zoster virus: Herpesvirus family
- Enveloped DNA
- Single serotype
Varicella (Chickenpox) transmission…
- Host: humans
- Respiratory droplets and direct contact w/lesions
- Mucosa of URT
- blood –> skin
- Sensory neurons: travels to dorsal root ganglia then becomes latent
Varicella (Chickenpox) signs and symptoms…
- Incubation: 14-21 days
- Prodrome: fever & malaise
- Papulovesicular rash in trunk and spreads to head/extremities
- Pruritis (itchy skin): Papule, Blister, Ulser
Varicella (Chickenpox) Prevent/Control…
- Diagnosed with Tzanck smear
- Antivirals: acyclovir, Foscarnet, Famciclovir, Valacyclovir
- Live, attenuated vaccines
- Varicella
- Zoster (14x more virus)
- varicella-zoster immune globulin
Varicella (Chickenpox) complications…
- Varicella pneumonia
- Encephalitis
- Reye’s syndrome
- Postherpetic neuralgia(Shigls)
Herpes Zoster (Shingles) signs and symptoms…
-Painful vesicles along course of sensory nerve of the head or trunk
Measles Infectious agents
- Morbillivirus: paramyxovirus fam.
- Enveloped (–) RNA
- 2 envelope spikes
- Hemagglutinin
- Cell fusing & hemolytic activity
- single serotype
Measles Transmission
- Host: humans
- Person-to-person contact through respiratory droplets
- URT –> Mucosal epithelium
- Epidemics: winter & spring as well as unimmunized/ partially immunized
Measles Signs and symptoms
Incubat: 7-18 days (usually 9-11)
- Fever, cough, coryza, conjunctivis
- 1-3 days later: KOPLIK SPOTS lasting 1-2 days
- 1 day later: rash (head trunk/extremities) lasting 3-5 days
Measles prevention/control
- Live attenuated vaccine
- Immune serum globulin
Measles complications
- Varicella pneumonia
- Encephalitis
- Reye’s syndrome
Roseola infectious agents
- Hum. herpesvirus 6 or 7: Herpesvirus family
- Enveloped DNA
Roseola transmission
-Mainly through saliva
Roseola signs and symptoms
- Fever x3 days
- Faint maculopapular rash spreading from trunk –> extremities
Mumps infectious agents
- Mumps virus: Paramyxovirus fam.
- Enveloped (–) RNA
- 2 envelope spikes
- single serotype
Mumps transmission
- Host: humans
- Droplets or DC w/ fomites
- URT: blood –> saliv. glands (testes, ovaries, pancreas, meninges)
Mumps signs and symptoms
- Incubation: 18-21 days
- Duration: 1 week
- Prodrome: fever, malaise, anorexia
- Tender salivary gland swelling
- Peak: late winter, early spring
Mumps control/prevention
Live, attenuated vaccine
Mumps complications
- Orchitis in post-pubertal males
- Meningitis
Rubella - “german” measles infectious agent
- Rubella virus: Togavirus family
- Enveloped (+) RNA
- 2 envelope glycoproteins
- single serotype
Rubella - “german” measles transmission
Host: humans
- Respiratory droplets
- URT: Blood lymph tissue, skin, organs
- Transplacental spread to fetus = congenital rubella
Rubella - “german” measles signs and symptoms
- Incubation: 14-21 days
- Duration: 1-3 days
- Low grade fever, upper respiratory sxs, lymphadenopathy
- W/in 24 hours faint, macular rash to head, neck and trunk as well as petechial lesions over soft palate
Rubella - “german” measles control/prevention
-Live, attenuated vaccine
Rubella - “german” measles complications
- Arthritis (days – 3 weeks)
- Thrombocytopenic purpura
- Encephalitis
Fifth disease – erythema infectiosum infectious agent
- Parovirus B19: Parvovirus family
- Naked single strand DNA
Fifth disease – erythema infectiosum transmission
- Host: humans
- Respiratory or DC w/fomite
- Blood or blood products
- Vertical transmission
- Winter to early summer
Fifth disease – erythema infectiosum signs and symptoms
Incubation: 4-12 days
- Duration: 1-2 weeks
- Fever, malaise, headache, myalgias, pruritis
- CHARACTERISTIC ‘BLUSH’ RASH: confluent, indurated rash to face
- 1-2 days later macular, reticular rash to arms and legs
- Lymphadenopathy, splenomegaly, mild leukopenia, anemia
Fifth disease – erythema infectiosum control/prevention
Immunogloblin may be useful (immunodeficiency)
Fifth disease – erythema infectiosum complications
- Hepatitis
- Thrombocytopenia
- Nephritis
- Encephalitis
- In pregnancy: profound anemia of fetus
What are the gastrointestinal virus infections?
- Rotavirus
- Norwalk virus
- Hepatitis A, B, C, D, E
Rotavirus infectious agents
- Rotavirus: Reoviridae family
- Naked double strand RNA
Rotavirus transmission
- Host: humans, animals (calves, mice, piglets, foals) but no interspecies spread
- Fecal-oral route
- Localize in duodenum and proximal jejunum
- cooler months
Rotavirus signs and symptoms
- Incubation: 1-3 days
- Duration: vomiting 1-3 days; diarrhea 4-8 days
- Abrupt onset of vomiting, then hours later watery/brown stools
- Low grade fever
Rotavirus control/prevention
- live, oral rotavirus vaccine
- rigorous hygiene measures
Rotavirus complications
Dehydration
Norwalk virus infectious agents
- Norovirus: Calciviridae family
- Naked (+) RNA
- 4 serotypes
Norwalk virus transmission
- Fecal-oral
- Consumption of contaminated food, water, uncooked shellfish & other foods
Norwalk virus signs and symptoms
- Incubation: 10-51 hours
- Abrupt onset vomiting & diarrhea
- Duration: 1-2 days
Norwalk virus control/prevention
Hygiene
Norwalk virus complications
Dehydration
Hepatitis A infectious agent
- Hepatitis A: Picornaviridae family
- Naked (+) RNA
Hepatitis A transmission
- Host: humans, primates
- Fecal-oral (contaminated food, water)
Hepatitis A signs and symptoms
- Incubation: 15-45 days
- Duration: days-weeks
- Fever, anorexia, nausea, RUQ pain, jaundice, dark urine, clay-colored stools, hepatomegaly
Hepatitis A control/prevention
- Avoidance of exposure
- Passive immunity- immune serum globulin
- Active immunization – killed HAV vaccine
Hepatitis B infectious agent
- Hepadnaviridae agent
- Enveloped, DNA (partially double stranded)
- 4 serotypes
Hepatitis B transmission
- Host- humans
- Vertical, parenterally, sexual contact
Hepatitis B signs and symptoms
- Incubation: 30-180 days (avg 10 wks)
- Duration: several months
- Fatigue, anorexia, nausea, RUQ pain/fullness, +/- arthralgias, rash, clay colored stools, dark urine, jaundice
Hepatitis B control/prevention
- Interferon and nucleoside and nucleotide analogs
- Hep B immune globulin
- Recombinant vaccine
Hepatitis B complications
-Fulminant hepatitis leading to liver necrosis & death; chronic hepatitis associated with cirrhosis, liver failure, HCC
Hepatitis D infectious agents
-Enveloped RNA
Hepatitis D transmission
-Requires Hep B surface antigen for transmission
Hepatitis D signs and symptoms
- Simultaneous D & B infection – looks like HAV or HBV
- Chronic HBV with superimposed hep D – jaundice relapse & high risk chronic cirrhosis
Hepatitis D control/prevention
- Interferon and nucleoside and nucleotide analogs
- Hep B immune globulin
- Recombinant vaccine
Hepatitis D complications
-Progressive liver disease, chronic cirrhosi
Hepatitis C infectious agents
- Flaviviridae family
- Enveloped (+) RNA
- 11 genotypes, multiple subtypes
Hepatitis C transmission
- Hosts: humans
- Parenterally, may be sexually transmitted
Hepatitis C signs and symptoms
- Incubation: 6-12 weeks
- Asymptomatic
- Chronic carrier state in 85%
- 10-18 years to develop chronic hepatitis
Hepatitis C control/prevention
- Interferon-α , ribavirin, HCV protease inhibitors
- No active or passive immunity
Hepatitis C complications
-Cirrhosis, increased HCC risk
Hepatitis E infectious agent
Naked (+) RNA
Hepatitis E transmission
- Host: humans
- Fecal-oral route
Hepatitis E signs and symptoms
- Incubation: 40 days
- Duration: 1-2 weeks
- Often subclinical
- Jaundice, anorexia, hepatomegaly, N/V, fever
Hepatitis E control/prevention
No active or passive immunity
Hepatitis E complications
When symptomatic can be fatal (esp. in pregnancy)
What are the Central Nervous System virus Diseases?
- Enterovirus
- Arboviruses: Meningitis & Encephalitis
- Rabies encephalitis
Enterovirus specific groups
- Poliovirus
- Coxsackievirus Group A
- Coxsackievirus Group B
- Echovirus, parechovirus & enterovirus
Enterovirus infectious agents
- Picornaviridae family
- Naked (+) RNA
Enterovirus transmission
- Fecal-oral route
- Infects GI & upper respiratory tract
- Spreads to target organs: CNS, heart, vascular endothelium, liver, pancreas, lungs, gonads, skeletal, muscles, synovial tissues, skin
- Increased prevalence – summer, fall
Enterovirus signs and symptoms
Incubation varies: 2-10 days
Enterovirus control/prevention
Inactivated poliovirus vaccine
Arboviruses – arthropod borne infectious agents
- Togavirus: enveloped (+) RNA: Alphaviruses & rubivruses
- Flavivirus: enveloped (+) RNA
- Bunyavirus: enveloped (–) RNA
Arboviruses – arthropod borne transmission
- Infected blood-sucking insects (mosquitoes, ticks, sandflies)
- Primarily occur in tropics
Arboviruses – arthropod borne signs and symptoms
- Acute febrile illness
- Encephalitis
- Meningitis
Arboviruses – arthropod borne control/prevention
-Immunizations for yellow fever, tick-borne, and Japanese B encephalitis
Rabies encephalitis infectious agent
- Rhabdoviridae family
- Enveloped (–) RNA
Rabies encephalitis transmission
- Host: All mammals
- Infected secretions (usually bite)
- Site of entry: multiplies in muscle cells then travels to CNS to replicate in brain cells
Rabies encephalitis signs and symptoms
-Incubation: 10 days – 1 yr
-Median survival after becoming symptomatic: 4 days, maximum 20 days
… then you are fucked
Rabies encephalitis control/prevention
- Pre-exposure: inactivated vaccine
- Post-exposure: human hyperimmune antirabies globulin plus rabies vaccine
Human Immunodeficiency Virus (HIV-1) infectious agent
Retrovirus family: Lentivirus genome -2 copies of enveloped (+) RNA -3 enzymes essential for viral replication 1. Reverse transcriptase: RNA --> double stranded DNA copy --> integrated into host chromosome 2. Protease 3. Integrase -Envelope contains 2 viral glycoproteins gp120 + gp41
Human Immunodeficiency Virus (HIV-1) transmission
Requires intimate contact with infecting source (bodily fluid, blood)
- Majority from sexual contact
- Perinatal transmission
- Virus has been detected in saliva, tears, urine but not shown to be infectious sources
- Primarily infects and kills helper (CD4) T lymphocytes
Human Immunodeficiency Virus (HIV-1) Infectious Cycle
Acute stage: 2-4 weeks after infection
- Fever, lethargy, sore throat, generalized lymphadenopathy, maculopapular rash (trunks, extremities), leukopenia
Latent stage: 7-11 years
- Asymptomatic
- Virus produced and sequestered in lymph nodes
Immunodeficiency stage (AIDS)
- Decline in CD4 cells
Human Immunodeficiency Virus (HIV-1) control/prevent
Appropriate screening
- Avoid exposure
- Antiretrovirals
- Pre- and post-exposure prophylaxis
