Respiratory tract infections Flashcards
List the clinical terms to describe infection of the - Nose - Throat - Sinuses - Ear - Epiglottis - Larynx
- Rhinitis
- pharyngitis
- sinusitis
- ottitis
- epiglottitis
- laryngitis
Distinguish between upper and lower resp tract infections
Lower- BELOW LARYNX- life threatening- viruses and bacteria
bronchitis, bronchiolitis, pneumonia
Upper- acute infection- viral- nose sinuses pharynx larynx, tonsilitis, pharyngitis, laryngitis, otitis, common cold
Describe causes of coryza (common cold) and effects
Adenoviruses Rhinoviruses >1000 serotypes Enteroviruses- coxsackie, echos (babies, kids) Corona viruses eg SARS MERS Respiratory syncytial viruses
can lead to secondary bacterial infections
Describe causes of pharyngitis and tonsillitis and effects
Viruses (adenomas), EB virus, streptogene bacteria
white tonsils due to EB virus
Describe epiglottitis
Bacterial, life threatening, swell–block airway
Haemophilus influenzae type b (now rare)- EFFECTIVE VACCINE
Describe croup
Young children- inspiratory stridor- narrowed airways
Noisy expiration
due to viruses such as paraflu, RSV
Describe the features and causative agents of infectious mononucleosis
Glandular fever is a syndrome not an aetiological diagnosis
Features- pharyngitis, lymphadenopathy (cervical, generalised), fever, malaise
Atypical mononuclear cells in periphery, activated Tc cells and CD8
Causes: EB virus
Cytomegalovirus
Toxoplasmosis (parasite)
HIV seroconversion
List viral causes of LRTIs
- Influenza, resp syncytial virus
- Rarely- varicella voster (adults)
- Measles virus (giant cell pneumonia)
- Cytomegalovirus (immunocompromised)
- MERS (and SARS) coronaviruses
Describe the features, symptoms, pathogenesis and complications of influenza virus
Features:
- Segmented single stranded RNA genome (ssRNA)
- 8 segments encode 11 proteins.
- 4 haemaglutinic acid binds sialic acid on cells to initiate infection
Symptoms:
- Respiratory tract symptoms e.g. rhinitis, cough, shortness of breath
- Systemic symptoms e.g. fever, headaches, myalgia
Influenza- 3 types - A, B, C. A has subtypes
Pathogenesis
- Pneumotropic- infects cells lining resp tract–down to alveoli
- Is lytic- strips off resp epi- exoliate epi cells
- Remove innate defence mechanisms- mucus and cilia
- Interferon production – circulates in blood (virus doesn’t)
Complications
- In the respiratory tract – pneumonia – 2 types
- 1° viral pneumonia: mononuclear cell infiltrate
- 2° bacterial pneumonia: PMNL infiltrate
- Cardiovascular complications
myocarditis
- Central nervous system complications
Encephalitis
Describe antigenic drift
Happens in A and B
random spontaneous mutation in viral genome
encode HA and NA- 1-2% AA sequence change
- Mutations clustered in HA and NA- Darwinian evolution- selected by host immune response
Describe antigenic shift
Genetic reassortment between human and non human virus- new subtypes
A
20% AA difference- new pandemic strains against pop which has no immunity
- Large % of pop infected in epidemic become immune, next epidemic 4-5 years
Define the terms epidemic and pandemic
Epi- widespread occurence of influenza in community at a particular time
Pan- Epidemic spreads on worldwide scale and infects large proportion of pop
Describe the clinical features of RSV
Causes LRTI in infants – bronchiolitis, pneumonia
• High hospitalisation rates
• Low mortality (<0.5%) unless
o Congenital heart disease
o Congenital lung disease (incl. prematurity)
o Immunodeficiency (congenital or acquired)
Requires rapid diagnosis and appropriate infection control measures
• Re-infection occurs throughout life - antigenic drift
Describe the diagnosis of community acquired pneumonia and groups in which it is more common
Pulmonary shadowing on CXR and new or existing LRTI symptoms
Males, elderly, chronic illness, alcoholics
Describe the aetiology of CAP
60-80% caused by conventional bacteria
Atypical bacteria and viruses cause the rest
