Respiratory Tract Viruses Flashcards
1
Q
Examples of resp tract viruses (6)
A
- Influenza (orthomyxovirus)
- Parainfluenza (paramyxovirus)
- Respiratory Syncytial Virus, metapneumovirus (paramyxovirus)
- Adenovirus
- Rhinovirus (picornavirus)
- Coronavirus
2
Q
Structure of influenza virus
A
- Envelope
- Haemagglutinin - for attachment to host cells, antigenic variation
- Neuraminidase - facilitates release of virus from infected cell - Nucleocapsid
- 8 discrete RNA segments
- 3 types of RNA polymerase
3
Q
Variations of influenza virus
A
- Type specific antigenicity - soluble/s antigen in ribonucleoprotein core
- Subtype specific antigenicity - based on H & N expressed
4
Q
Epidemiology of influenza
A
- Influenza A - pandemics
- Influenza B - periodic epidemics
- Influenza C - less common, mild, no outbreaks
- Epidemics result from antigenic variation
1. Antigenic shift - genetic reassortment leading to antigenic change of both surface components
2. Antigenic drift - spontaneous mutation leading to minor changes in haemagglutinin
5
Q
Transmission of influenza
A
Respiratory droplets
6
Q
Incubation period of influenza
A
Short, 1-4 days
7
Q
Symptoms of influenza (2)
A
- Abrupt onset of fever, myalgia, malaise, headache
- Sore throat, dry cough, sneezing, rhinorrhea - viral multiplication in resp epithelium causes desquamation & ciliary damage
8
Q
Complications of influenza (4)
A
- Pneumonia - primary viral, secondary bacterial (damage of bronchial mucosa) caused by strep pneum, staph aureus, h influenzae
- Myocarditis - inflamm of heart muscle
- Myositis - inflamm of skeletal muscle
- Reye’s syndrome
- assoc w influenza B & aspirin intake in children, high mortality
- cerebral edema, fatty degeneration of liver
9
Q
Diagnosis of influenza (3)
A
- Virus isolation (chick embryo, monkey kidney cells - typing by HI)
- IF of antigen in resp epithelial cells
- Serology
10
Q
Treatment of influenza (5)
A
- Antivirals - Neuraminidase inhibitors (Oseltamivir/tamiflu, Zanamivir/Relenza), Amantadine (influenza A)
- Symptomatic treatment, recognise & treat complications, exclude differential diagnoses
- Minimise spread by resp route
- Vaccine (antigens from 2 influenza A & 1 influenza B strain) - inactivated, killed (IM) or live (nasal spray), problems of timely preparation, short lived immunity, incomplete protection, Guillain-Barre syndrome
- Prophylactic immunisation (for high risk groups, risk periods eg winter)
11
Q
Structure of parainfluenza virus
A
enveloped helical RNA virus with no genetic recombination
12
Q
Variations of parainfluenza virus
A
four serotypes
- Type 1: Croup in infants
- Type 2: Epidemics in winter
- Type 3: Bronchiolitis & bronchopneumonia in young infants, croup in older infants
- Type 4: minor resp infection
13
Q
Epidemiology of parainfluenza
A
- infects animals & man
- infection acquired by age 5
14
Q
Symptoms of parainfluenza (4)
A
- Febrile common cold - sore throat, cough, hoarseness
- URTI - croup - acute laryngotracheobronchitis, cough, hoarseness; if severe, dyspnea, stridor, cyanosis (may req tracheostomy)
- LRTI - bronchiolitis, bronchopneumonia
- DDx - diphtheria, H. influenzae epiglottitis
15
Q
Diagnosis of parainfluenza (3)
A
- Tissue culture (monkey kidney cells, CPE by type 2, guinea pig RBC haemagglutination)
- IF of infected resp epithelial cells (antigen detection)
- Serology - detect antibodies to
- s (soluble antigen) - nucleocapsid - early
- v (viral antigen) - H & N - late
16
Q
Treatment of parainfluenza (4)
A
- Ventilatory support eg tracheostomy
- Sedation (agitation from dyspnea) & hydration (replace lost fluid while breathing)
- Antibiotics for secondary bacterial infection (+/- prophylactic)
- No vaccine
17
Q
Structure of RSV
A
enveloped helical RNA virus with no H/N
18
Q
Symptoms of RSV (3)
A
- Bronchiolitis - commonest cause in young children, peak at 3m
- fever, cough, dyspnea, tachypnea, wheezing, cyanosis, inspiratory withdrawing
- immune mediated/mechanical obstruction of narrow bronchioles by inflamm process - Severe Pneumonia - may result from reaction between virus & maternal Abs
- URTI in older children/adults (larger bronchioles, less likely to be blocked by inflamm)
19
Q
Complications of RSV (5)
A
- Secondary bacterial infection
- Otitis Media
- Cardiac failure
- Apnea
- bronchiolitis & pneumonia - up to 5% mortality (increased mortality assoc w CNS malformations & congenital disease of the heart/lungs)
20
Q
Diagnosis of RSV (3)
A
- Tissue culture - inoculate HeLa/Hep-2 cells, highly characteristic refractile syncytium formation of multinucleated giant cells
- IF of nasopharyngeal aspirates (antigen detection)
- Serology (1 serotype)
21
Q
Treatment of RSV (3)
A
- Antiviral - Ribavirin aerosol therapy
- Ventilatory support, isolate infected hospitalised children
- No effective vaccine
22
Q
Features of metapneumovirus
A
- similar symptoms to RSV
- associated with infants & children with acute resp disease & asthma in children
23
Q
Structure of adenovirus
A
- Non enveloped icosahedral virion with projecting fibres
- ds DNA
variations: >40 recognised serotypes
24
Q
Symptoms of adenovirus (8)
A
- infects mucosa & lymphoid tissue
- Pharyngoconjunctival fever - spread in swimming pools
- URTI/pharyngitis w fever
- Pneumonia
- Acute follicular conjunctivitis
- Epidemic keratoconjunctivitis/shipyard eye
- Haemorrhagic cystitis (bladder inf)
- Enteritis
- mesenteric adenitis (inflammation of mesentery lymph nodes)
- intussusception (interference with peristalsis) - Chronic infection of tonsils & adenoids
25
Diagnosis of adenovirus (2)
1. Tissue culture - swelling/clustering of infected cells w intranuclear inclusions (bunch of grapes)
2. Serology
- IF for rapid detection of viral antigen
- CFT to adenovirus common group antigen
- NT
26
Treatment of adenovirus
1. Vaccine for certain serotypes, used for military recruits
27
Structure of rhinovirus
- non enveloped, icosahedral, ssRNA
| - variations >100 serotypes, may undergo genetic/antigenic variation
28
Incubation period of rhinovirus
2-4 days
29
Transmission of rhinovirus
- inhabit upp resp tract
| - readily spread by close contact & resp secretions
30
Symptoms of rhinovirus
- Main cause of common cold (lasts 1-2 weeks)
| - rhinorrhea, sneezing, sore throat, cough, hoarseness, mild fever, headache
31
Complications of rhinovirus
- may precipitate asthmatic attacks & aggravate chronic bronchitis
- rare: sinusitis, otitis media, pneumonia
32
Diagnosis of rhinovirus (2)
1. Tissue Culture
- unstable below pH6, optimal growth at 33C
- CPE in human embryo lung & monkey kidney cells (H&M rhinovirus)
2. Serology - NT
33
Treatment of rhinovirus (2)
1. Symptomatic
| 2. No vaccine
34
Structure of coronavirus
enveloped with crown-like projections, RNA
35
Variations of coronavirus
at least 3 antigenic types (with some cross reactivity)
36
Clinical presentation of coronavirus
- Mucosal infections in domestic animals
- Common cold in man
- SARS is due to an animal version of coronavirus - resp route transmission, req ventilatory support, quarantine
37
Diagnosis of coronavirus
Tissue culture
- difficult, isolated in human embryo trachea cultures
- CPE in human embryo lung cell line
38
Treatment of coronavirus
- no specific treatment
| - no vaccine
