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microb - viruses > Respiratory Tract Viruses > Flashcards

Respiratory Tract Viruses Flashcards

1
Q

Examples of resp tract viruses (6)

A
  1. Influenza (orthomyxovirus)
  2. Parainfluenza (paramyxovirus)
  3. Respiratory Syncytial Virus, metapneumovirus (paramyxovirus)
  4. Adenovirus
  5. Rhinovirus (picornavirus)
  6. Coronavirus
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2
Q

Structure of influenza virus

A
  1. Envelope
    - Haemagglutinin - for attachment to host cells, antigenic variation
    - Neuraminidase - facilitates release of virus from infected cell
  2. Nucleocapsid
    - 8 discrete RNA segments
    - 3 types of RNA polymerase
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3
Q

Variations of influenza virus

A
  • Type specific antigenicity - soluble/s antigen in ribonucleoprotein core
  • Subtype specific antigenicity - based on H & N expressed
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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
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5
Q

Transmission of influenza

A

Respiratory droplets

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6
Q

Incubation period of influenza

A

Short, 1-4 days

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7
Q

Symptoms of influenza (2)

A
  1. Abrupt onset of fever, myalgia, malaise, headache
  2. Sore throat, dry cough, sneezing, rhinorrhea - viral multiplication in resp epithelium causes desquamation & ciliary damage
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8
Q

Complications of influenza (4)

A
  1. Pneumonia - primary viral, secondary bacterial (damage of bronchial mucosa) caused by strep pneum, staph aureus, h influenzae
  2. Myocarditis - inflamm of heart muscle
  3. Myositis - inflamm of skeletal muscle
  4. Reye’s syndrome
    - assoc w influenza B & aspirin intake in children, high mortality
    - cerebral edema, fatty degeneration of liver
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9
Q

Diagnosis of influenza (3)

A
  1. Virus isolation (chick embryo, monkey kidney cells - typing by HI)
  2. IF of antigen in resp epithelial cells
  3. Serology
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10
Q

Treatment of influenza (5)

A
  1. Antivirals - Neuraminidase inhibitors (Oseltamivir/tamiflu, Zanamivir/Relenza), Amantadine (influenza A)
  2. Symptomatic treatment, recognise & treat complications, exclude differential diagnoses
  3. Minimise spread by resp route
  4. 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
  5. Prophylactic immunisation (for high risk groups, risk periods eg winter)
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11
Q

Structure of parainfluenza virus

A

enveloped helical RNA virus with no genetic recombination

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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
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13
Q

Epidemiology of parainfluenza

A
  • infects animals & man

- infection acquired by age 5

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14
Q

Symptoms of parainfluenza (4)

A
  1. Febrile common cold - sore throat, cough, hoarseness
  2. URTI - croup - acute laryngotracheobronchitis, cough, hoarseness; if severe, dyspnea, stridor, cyanosis (may req tracheostomy)
  3. LRTI - bronchiolitis, bronchopneumonia
  4. DDx - diphtheria, H. influenzae epiglottitis
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15
Q

Diagnosis of parainfluenza (3)

A
  1. Tissue culture (monkey kidney cells, CPE by type 2, guinea pig RBC haemagglutination)
  2. IF of infected resp epithelial cells (antigen detection)
  3. Serology - detect antibodies to
    - s (soluble antigen) - nucleocapsid - early
    - v (viral antigen) - H & N - late
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16
Q

Treatment of parainfluenza (4)

A
  1. Ventilatory support eg tracheostomy
  2. Sedation (agitation from dyspnea) & hydration (replace lost fluid while breathing)
  3. Antibiotics for secondary bacterial infection (+/- prophylactic)
  4. No vaccine
17
Q

Structure of RSV

A

enveloped helical RNA virus with no H/N

18
Q

Symptoms of RSV (3)

A
  1. 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
  2. Severe Pneumonia - may result from reaction between virus & maternal Abs
  3. URTI in older children/adults (larger bronchioles, less likely to be blocked by inflamm)
19
Q

Complications of RSV (5)

A
  1. Secondary bacterial infection
  2. Otitis Media
  3. Cardiac failure
  4. Apnea
  5. 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
  1. Tissue culture - inoculate HeLa/Hep-2 cells, highly characteristic refractile syncytium formation of multinucleated giant cells
  2. IF of nasopharyngeal aspirates (antigen detection)
  3. Serology (1 serotype)
21
Q

Treatment of RSV (3)

A
  1. Antiviral - Ribavirin aerosol therapy
  2. Ventilatory support, isolate infected hospitalised children
  3. 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
  1. Pharyngoconjunctival fever - spread in swimming pools
  2. URTI/pharyngitis w fever
  3. Pneumonia
  4. Acute follicular conjunctivitis
  5. Epidemic keratoconjunctivitis/shipyard eye
  6. Haemorrhagic cystitis (bladder inf)
  7. Enteritis
    - mesenteric adenitis (inflammation of mesentery lymph nodes)
    - intussusception (interference with peristalsis)
  8. Chronic infection of tonsils & adenoids
25
Q

Diagnosis of adenovirus (2)

A
  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
Q

Treatment of adenovirus

A
  1. Vaccine for certain serotypes, used for military recruits
27
Q

Structure of rhinovirus

A
  • non enveloped, icosahedral, ssRNA

- variations >100 serotypes, may undergo genetic/antigenic variation

28
Q

Incubation period of rhinovirus

A

2-4 days

29
Q

Transmission of rhinovirus

A
  • inhabit upp resp tract

- readily spread by close contact & resp secretions

30
Q

Symptoms of rhinovirus

A
  • Main cause of common cold (lasts 1-2 weeks)

- rhinorrhea, sneezing, sore throat, cough, hoarseness, mild fever, headache

31
Q

Complications of rhinovirus

A
  • may precipitate asthmatic attacks & aggravate chronic bronchitis
  • rare: sinusitis, otitis media, pneumonia
32
Q

Diagnosis of rhinovirus (2)

A
  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
Q

Treatment of rhinovirus (2)

A
  1. Symptomatic

2. No vaccine

34
Q

Structure of coronavirus

A

enveloped with crown-like projections, RNA

35
Q

Variations of coronavirus

A

at least 3 antigenic types (with some cross reactivity)

36
Q

Clinical presentation of coronavirus

A
  • 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
Q

Diagnosis of coronavirus

A

Tissue culture

  • difficult, isolated in human embryo trachea cultures
  • CPE in human embryo lung cell line
38
Q

Treatment of coronavirus

A
  • no specific treatment

- no vaccine

microb - viruses (10 decks)

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