Viruses Flashcards
What family is the influenza virus?
Orthomyxovirus famly
What are 3 features of the structure of the influenza virus?
- 100nm
- Envelope
- Nucleocapsid
What is the envelope of the influenza virus made of?
- Composed of lipoprotein
- Covered with glycoprotein surface projections
- hemagluttinin (spikes for virus attachment to cells; type and strain specific antigens) = causes agglutination of various animal erythrocytes
- neuraminidase - cleaves neuraminic acid (sialic acid) receptors to allow virus release
What is the nucleocapsid of influenza virus made of?
- 8 discrete RNA segments randomly incorporated into virion during maturation
- 3 types of RNA polymerase
- Type-specific antigenicity - influenza A, B, C
What is the incubation period for influenza?
1-4 days
Symptoms of influenza?
- Onset of fever, myalgia, malaise, headache
- Rhinorrhoae, Sneezing
- Sore throat, dry cough (due to viral multiplication in respiratory epithelium causing desquamation and ciliary damage)
What are 4 complications of influenza?
- Pneumonia
- Primary Viral
- secondary bacterial (s. pneumoniae, h. influenzae, s. aureus) - Myocarditis
- Myositis
- Reye’s Syndrome (cerebral edema, fatty degeneration, high mortality)
What 4 tests can be done in the lab to diagnose influenza?
- immunofluorescence (IF) of antigen in respiratory epithelial cells
- RT-PCR
- Point of Care Tests (lateral flow)
- Serology
What are two components making up the antigenic structure of the influenza virus?
- Soluble ‘s’ antigen
- in ribonucleoprotein core
- same antigen shared by all influenza A viruses etc - Hemagglutinin
- main neutralising antigen responsible for host immunity
What are the 3 types of influenza viruses and their significance?
- Influenza A - epidemics, pandemics
- Influenza B - Periodic epidemics
- Influenza C - less common
How do flu epidemics arise?
Antigenic Variation
How may antigenic variation of flu virus occur?
- Antigenic Shift - recombination of RNA segments of two antigenic types simultaneously infecting the same cell between different animal virus strains ; resulting in major antigenic change of both surface components
- Antigenic Drift
- Spontaneous mutations leading to minor changes in hemagglutinin
How many types of hemagglutinin and neuraminidase are there?
18 (H) and 11 (N)
How to treat influenza?
- Symptomatic treatment
- Recognise and treat complications
- Neuraminidase inhibitors (oseltamivir/zanamivir) & polymerase inhibitors (baloxavir)
- Wear mask
- Amantadine (but resistance is common)
What are two types of vaccines for flu?
- Inactivated vaccine comprising antigens from circulating A/H1N1, A/H3N2, B strains
- Quadrivalent vaccine to cover B/Victoria & B/Yamagata lineages
When is flu vaccine given? What are issues with it?
Annually during winter season for high risk groups.
Problems of timely preparation, short lived immunity, incomplete protection, rarely Guillain-Barre Syndrome
What are paramyxoviruses? Give 4 examples too.
Enveloped helical RNA viruses.
- Parainfluenza
- Respiratory Syncytial Virus
- Measles Virus
- Mumps
Does genetic recombination occur in paramyxoviruses?
No
What are the four serotypes of parainfluenza virus and generally what do they cause?
Type 1 - Croup in infants
Type 2 - Epidemics (winter)
Type 3 - Bronchiolitis and Bronchopneumonia, croup in older infants
Type 4 - Minor Respiratory Infection
What does parainfluenza virus infect?
Animals and Humans (acquired by 5 yo)
What are the typical symptoms of parainfluenza virus?
- Febrile common cold - sore throat, cough, hoarseness
- Croup - acute laryngo-tracheo-bronchitis; cough, hoarseness; (severe) dyspnea, stridor, cyanosis; ddx: diptheria, h influenza epiglottitis
- Bronchiolitis
- Bronchopneumonia
What are 4 methods to diagnose parainfluenza virus?
- Tissue culture in monkey kidney cells
- Antigenic detection (immunofluroescence of infected respitatory epithelial cells)
- RT-PCR
- Serology : detect antibodies to ‘s’ antigen (early) and ‘v’ antigen (hemagglutinin and neuraminidase) (late) *limited value
Methods to treat parainfluenza virus?
- Ventilatory support
- Antibiotics for secondary bacterial infection
- Sedation and hydration
*no vaccine
Does RSV have hemagglutinin and neuraminidase?
No
What are symptoms of RSV?
- Bronchiolitis in young children (fever, cough, dyspnea, tachypnea, wheezing, cyanosis, inspiratory indrawing)
- severe pneumonia from reaction between virus and maternal antibodies
- immune-mediated and/or mechanical obstruction of narrow bronchioles by inflammatory process
*5% mortality in bronchiolitis and pneumonia - Upper respiratory tract infection in older children and adults
What are complications of RSV?
Secondary bacterial infections, otitis media, cardiac failure, apnea
What are 4 methods of diagnosing RSV?
- Tissue culture = highly characteristic refractile syncytium formation of multinucleated giant cells
- Viral antigen demonstration (IF of nasopharyngeal aspirates)
- RT-PCR
- Serology - one serotype only
How can RSV be treated?
- Ribavirin aerosol therapy
- Ventilatory support
3 Isolate infected children - RSV immunoglobulin (palivizumab) to protect infants at risk of severe RSV disease
*no vaccine
What is a differential of RSV?
Metapneumovirus
What is metapneumovirus associated with?
- Infants and children with acute respiratory disease
- Asthma in children - acute wheezing attacks
- Symptoms similar to RSV
What is an adenovirus?
Icosahedral DNA virions with cubic symmetry and projecting fibres
What part does adenoviruses infect?
- Mucosa and lymphoid tissue
What are 8 symptoms of adenovirus infection?
- Pharyngoconjunctival fever (occasionally epidemic, usually type 3, swimming pool)
- URTI with fever (pharyngitis)
- Pneumonia
- Acute follicular Conjunctivitis
- Epidemic keratoconjunctivitis (shipyard eye)
- Hemorrhagic cystitis
- Enteritis - mesenteric adenitis & intussusception
- Chronic infection of tonsils and adenoids
What are 3 methods of diagnosing adenoviruses?
- Tissue culture (swelling and clustering infected cells with intranuclear inclusions [‘bunch of grapes’]
- Serology (IF for rapid detection of viral antigen & Serotyping by NT)
- PCR
How can Adenovirus be controlled?
Vaccine against certain serotypes - for military recruits
What are picornaviruses?
Large family of animal viruses characterised by small size, naked icosahedral symmetry and ribonucleic acid genome
What are two genera of picornaviruses?
Rhinovirus and enterovirus
3 features of Rhinoviruses?
- More than 100 serotypes
- May undergo genetic/antigenic variation
- Inhabit upper respiratory tract
What is the incubation period of rhinovirus?
2-4days
Symptoms of rhinoviruses?
rhinorrhoae, sneezing, sore throat, cough, mild fever, hoarseness, headache
Complications of rhinoviruses?
Sinusitis, otitis media, pneumonia, precipitate asthmatic attacks, aggravate chronic bronchitis
How long does rhinovirus last?
1-2 weeks
how is rhinovirus spread?
- readily spread by close contact and respiratory secretions
How can rhinovirus be diagnosed?
- Tissue culture
- unstable below pH 6
- optimal growth 33 degrees
- CPE in humna embryo lung – H rhinovirus
- monkey kidney cells – M rhinoviruses - Serotyping – NT
- RT-PCR
How to treat rhinovirus?
- Symptomatic
- No vaccine
What are coronaviruses?
Enveloped RNA viruses of size 100nm, contain crown-like projections on virion surface
Comment on antigenic types of coronaviruses.
multiple antigenic types, with some cross reactivity
Examples of coronaviruses.
SARS, COVID-19, MERS
Do coronaviruses hemagglutinate RBCS?
yes
Effect of coronavirus in domestic animals?
Mucosal Infections
Comment on diagnoses and treatment of coronavirus.
Difficult to culture
No specific treatment
No routine vaccine
Compare cold and flu (10 points)
Cold vs Flu
Gradual onset vs Abrupt onset
Fever rare vs fever
Slight aches, fatigue vs aches common, fatigue
Chills uncommon vs chills common
Sneezing often vs sneezing sometimes
chest discomfort vs chest discomfort
Cough mild to moderate vs cough commin
stuffy nose common vs stuffy nose sometimes
sore throat common vs sore throat sometimes
headache rare vs headache common
