Respiratory Tract Infection PDF

Child block Respiratory tract infection college of medicine university of Garmian Samin Q.Mohamed M.B.Ch.b, C.A.B.P Pertussis (Bordetella pertussis) Pertussis is an acute respiratory tract infection; the term pertussis means “intense cough” and is preferable to whooping cough, because mo...

Child block Respiratory tract infection college of medicine university of Garmian Samin Q.Mohamed M.B.Ch.b, C.A.B.P Pertussis (Bordetella pertussis) Pertussis is an acute respiratory tract infection; the term pertussis means “intense cough” and is preferable to whooping cough, because most infected individuals do not “whoop.”  Pathogenesis Bordetella organisms are small, fastidious, gram-negative coccobacilli that colonize only ciliated epithelium. The exact mechanism of disease symptomatology remains unknown. Bordetella species share a high degree of DNA homology among virulence genes. Only B. pertussis expresses pertussis toxin (PT), the major virulence protein. PT has numerous proven biologic activities (e.g., histamine sensitivity, insulin secretion, leukocyte dysfunction).  Pertussis is extremely contagious , with attack rates as high as 100% in susceptible individuals exposed to aerosol droplets at close range. High airborne transmission rates were shown in a baboon model of pertussis despite vaccination with the acellular vaccine. B. pertussis does not survive for prolonged periods in the environment. Chronic carriage by humans is not documented. After intense exposure as in households, the rate of subclinical infection is as high as 80% in fully immunized or previously infected individuals. When carefully sought, a symptomatic source case can be found for most patients; usually a sibling or related adult. Clinical Manifestations Classically, pertussis is a prolonged disease, divided into catarrhal, paroxysmal, and convalescent stages. The catarrhal stage (1-2 wk) begins insidiously after an incubation period ranging from 3-12 days with nondistinctive symptoms of congestion and rhinorrhoea variably accompanied by low-grade fever, sneezing, lacrimation, and conjunctival suffusion. As initial symptoms wane, coughing marks the onset of the paroxysmal stage (2-6 wk). The cough begins as a dry, intermittent, irritative hack and evolves into the inexorable paroxysms that are the hallmark of pertussis. A well-appearing, playful toddler with insignificant provocation suddenly expresses an anxious aura and may clutch a parent or comforting adult before beginning a machine-gun burst of uninterrupted cough on a single exhalation, chin and chest held forward, tongue protruding maximally, eyes bulging and watering, face purple, until coughing ceases and a loud whoop follows as inspired air traverses the still partially closed airway. Posttussive emesis is common, and exhaustion is universal. The number and severity of paroxysms escalate over days to a week and remain at that plateau for days to weeks.  At the peak of the paroxysmal stage, patients may have >1 episode hourly. As the paroxysmal stage fades into the convalescent stage (≥2 wk), the number, severity, and duration of episodes diminish. Infants