1 respiratory infection
TRANSCRIPT
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Respiratory infection - 1
Dr Paul McIntyre
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Influenza - clinical presentation
• Fever: high, abrupt onset
• Malaise
• Myalgia• Headache• Cough• Prostration
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‘Flu - aetiology• Classical flu
– influenza A viruses
– influenza B viruses
• ‘Flu- like illnesses– parainfluenza viruses
– many others
• Haemophilus influenzae– bacterium
– not a primary cause of ‘flu– may be a secondary invader
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‘Flu - complications
• Primary influenzal pneumonia– seen most during pandemic years
– can be disease of young adults– high mortality
• Secondary bacterial pneumonia– more common in elderly and debilitated, pre-
existing disease– cause of mortality in all influenza epidemics
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‘Flu - therapy
• Symptomatic– bed rest, fluids, paracetamol
• Antivirals– oseltamivir– zanamivir
• see NICE guidelines www.nice.org.uk– ‘flu circulating– risk of complications
– use in prophylaxis (additional to vaccine)
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Epidemiology of ‘flu
• Winter epidemics
• Epidemics seen in association with minor mutations in the surface proteins of the virus– antigenic drift
• Pandemics: rare, unpredictable, influenza A– antigenic shift– segmented genome– animal reservoir/mixing vessel
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Current pandemic planning assumption
• the combination of “reasonable worst case” 30% Clinical Attack Rate and 0.1% Case Fatality Ratio would result in a total number of deaths of about 20,000, or about 1/30th of the total expected each year from all causes (about 600,000).
• These are planning assumptions for forthcoming winter, not predictions
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Novel Swine-Origin Influenza A (H1N1) Virus Investigation Team. N Engl J Med 2009;360:2605-2615
Comparison of H1N1 Swine Genotypes in Early Cases in the United States
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Future threats
• Highly pathogenic avian flu is influenza A H5N1
• bird to human transmission seen– High mortality
• not readily transmitted human to human
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11Egon Schiele,The Family,1918.Oesterreichische Galerie, Vienna
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Lab confirmation of influenza
• Direct detection of virus– PCR
• Throat swabs in virus transport medium• Pernasal swabs in virus transport medium• other respiratory samples
– Other labs may use immunofluorescence, antigen detection (near patient), virus culture
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Lab confirmation of influenza
• Direct detection of virus– PCR
• Antibody detection– may need paired acute and convalescent bloods– often retrospective
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PCR for Influenza A VirusPCR for Influenza A Virus
Influenza A RNAnegative samples
Influenza A RNA positive samples
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Prevention of ‘flu
• Vaccine– killed vaccine
– given annually to patients at risk of complications
– given to health care workers
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Antiviral as prophylaxis
• antivirals after a contact with ‘flu– NICE guidelines
– rarely used
• During “containment phase” of first wave of pandemic.
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Other causes of community acquired pneumonia
• Microbiological causes (all bacteria)– Mycoplasma pneumoniae
– Coxiella burnetii– Chlamydia
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Mycoplasma, coxiella and Chlamydophila psittaci
• Therapy– all respond to tetracycline and macrolides (eg
clarithromycin)
• Mortality– varies with pathogen, but generally lower than
classical bacterial pneumonia
• Often known as “atypical pneumonia”– relates to presentation and response to therapy
in the pre-antibiotic era
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Lab confirmation of mycoplasma, coxiella and
Chlamydophila psittaci• By serology
– send acute and convalescent bloods to lab
– gold top vacutainer
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Mycoplasma pneumoniae
• Common cause of community acquired pneumonia
• Older children, young adults
• Person to person spread
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Coxiella burnetii (Q-fever)
• Diseases– pneumonia– pyrexia of unknown
origin (Q fever)
• Uncommon, sporadic zoonosis
• Sheep and goats• Complication
– culture negative endocarditis
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Chlamydia and respiratory disease
• Chlamydophila psittaci causes Psittacosis– previously called Chlamydia psittaci
– uncommon, sporadic zoonosis – caught from pet birds
• parrots, budgies, cockatiels
– psittacosis usually presents as pneumonia
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Bronchiolitis• Clinical presentation
– 1st or 2nd year of life
– Fever– Coryza– Cough– Wheeze
• Severe cases– grunting
� ↓PaO2
– Intercostal / sternal indrawing
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Bronchiolitis - complications
• Respiratory and cardiac failure– prematurity
– pre-existing respiratory or cardiac disease
• Scottish Intercollegiate Guidelines Network– SIGN guideline 91
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Bronchiolitis
• Aetiology– >90% cases due to Respiratory Syncytial Virus
• Lab confirmation– By PCR on throat or pernasal swabs– (direct IF on NPA in some labs)
• Therapy– supportive– nebulised ribavirin no longer used
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Bronchiolitis - epidemiology and control
• Epidemics every winter
• Very common
• No vaccine
• Nosocomial spread in hospital wards– cohort nursing– handwashing, gowns, gloves
• Passive immunisation– poor efficacy and cost-effectiveness
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Metapneumovirus
• First isolated 2001 children with Acute Respiratory Tract Infection– Nat Med 2001;7:719-24.
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Epidemiology
• Most children antibody positive by age 5
• found in a wide range of ages
• Virus is newly discovered, not new
• World-wide distribution
• Highest incidence in winter– 8% of samples in Canadian children’s hospital
– J Clin Micro 2005;43:5520-5.
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Association with disease
• May be sole pathogen isolated • Possibly second only to RSV in bronchiolitis • Similar symptoms to RSV in both children and adults
• Range of severity from mild to requiring ventilation
• Incidence of asymptomatic infection low (in children at least)– Williams JV et al. NEJM 2004;350:443-50 (and editorial)
• 2% of cases of influenza-like illness– Emerging Infect Dis 2002;8:897-901
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Laboratory confirmation
• PCR
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Other recently discovered respiratory viruses
• Bocavirus
• Various coronaviruses
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Current Respiratory tests
• Samples for PCR: Throat swabs in viral transport medium, bronchoalveolar lavage (BAL), endotracheal aspirate etc– Flu A, Flu B, parainfluenza 1-3, metapneumo, adeno,
RSV
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Chlamydia trachomatis and Chlamydophila pneumoniae and
respiratory disease• Chlamydia trachomatis
– STI which can cause infantile pneumonia– diagnosed by PCR on urine of mother or
pernasal / throat swabs of child
• Chlamydophila pneumoniae– person to person (formerly Chlamydia
pneumoniae)– mostly mild respiratory infections
– may be picked up by test for Psittacosis
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Microbiology Problem Solving Session
• Remember to bring the relevant pages from the study guide with you to the class.
• Code for the classroom’s cloakroom is 1245
• Worthwhile looking at tuberculosis diagnosis and management before coming along.
• Remember to wash your hands before leaving the classroom as other students use live bacteria in their practicals in that room.
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Lecture objectives
• An understanding of the epidemiology, presentation, management and prevention of many of the most important viral and “atypical” causes of respiratory infection.