Final answer:
The three phases of a Bordetella pertussis infection are the catarrhal stage with mild symptoms and high infectiousness, the severe paroxysmal stage with prolonged coughing, and the convalescent stage where symptoms gradually subside.
Step-by-step explanation:
Phases of a Bordetella pertussis Infection
The infection caused by Bordetella pertussis, known as pertussis or whooping cough, progresses through three distinct stages:
- Catarrhal stage: The initial phase is marked by mild respiratory symptoms such as nasal congestion, runny nose, sneezing, and a low-grade fever. This stage is when B. pertussis is most infectious.
- Paroxysmal stage: This is the most serious stage, characterized by severe and prolonged coughing spells that may be accompanied by the characteristic "whooping" sound during inhalation due to the restricted airway.
- Convalescent stage: This final phase involves a gradual recovery with a decrease in the frequency and severity of coughing spells. However, coughing can persist for several weeks.
The paroxysmal stage is known to lead to complications due to the mucus accumulation in the lungs, fostering colonization by B. pertussis and secondary infections.