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Infectious disease and microbiology – Pertussis
Pertussis, commonly known as whooping cough, is a highly contagious respiratory infection caused primarily by Bordetella pertussis and less commonly by Bordetella parapertussis. Although vaccination has greatly reduced the disease burden in children, pertussis remains a worldwide health problem, especially among adolescents and adults, who may unknowingly transmit the infection to vulnerable infants.
The incidence among vaccinated children is significantly lower compared with unvaccinated populations, but outbreaks still occur. Infection rates remain considerable among older children and young adults due to waning immunity over time. Adults and older siblings often serve as reservoirs for transmission to infants who are either unvaccinated or incompletely vaccinated.
Prevention relies mainly on routine immunization, typically given in combination with diphtheria and tetanus vaccines during infancy and childhood, with booster doses later in life. Prophylactic antibiotics are recommended for close household contacts once a case is identified. Macrolides or trimethoprim-sulfamethoxazole are commonly used for this purpose.
The pathogenesis of pertussis involves colonization of the respiratory epithelium by the organism. Bordetella produces several toxins, including pertussis toxin and tracheal cytotoxin, which damage respiratory tissues and contribute to the characteristic prolonged cough. Inflammatory mediators such as bradykinin may also play a role in the persistent paroxysmal coughing spells.
After an incubation period of about 7–10 days, the disease classically progresses through three stages. The catarrhal phase resembles a mild upper respiratory infection with rhinorrhea, low-grade fever, and conjunctivitis. This is followed by the paroxysmal phase, characterized by severe bouts of coughing that may last several weeks. Finally, during the convalescent phase, coughing gradually improves over 1–2 weeks.
In young unvaccinated children, the hallmark finding is the “whoop,” a high-pitched inspiratory sound following a coughing fit. These episodes may be associated with cyanosis and vomiting. Adults and previously vaccinated individuals often present atypically with only a prolonged cough, which contributes to underdiagnosis and ongoing transmission.
Diagnosis is confirmed through culture or PCR testing of nasopharyngeal specimens, especially during the first two weeks of illness. Marked lymphocytosis may be present during the paroxysmal phase. Serologic testing demonstrating high antibody titers or a significant rise in antibodies can also support the diagnosis. Chest radiographs may show perihilar infiltrates, atelectasis, or consolidation in complicated cases.
Treatment is primarily supportive, especially in infants younger than one year, who are at greatest risk of severe disease. Antibiotics are mainly used to eradicate the organism and reduce transmission rather than shorten the duration of cough once the paroxysmal phase has begun. Macrolides such as azithromycin, clarithromycin, and erythromycin are the preferred agents. Trimethoprim-sulfamethoxazole is an alternative for patients who cannot tolerate macrolides.
Hospitalization may be required for infants, unvaccinated children, or patients with severe disease. Despite modern therapy, pertussis can lead to serious complications, particularly in infants, including pneumonia, apnea, seizures, encephalopathy, and death. Severe coughing can also cause subconjunctival hemorrhage, pneumothorax, rib fractures, rectal prolapse, and intracranial hemorrhage. Prognosis is generally excellent after recovery, although mortality remains highest among infants too young to be vaccinated.
Pertussis, commonly known as whooping cough, is a highly contagious respiratory infection caused primarily by Bordetella pertussis and less commonly by Bordetella parapertussis. Although vaccination has greatly reduced the disease burden in children, pertussis remains a worldwide health problem, especially among adolescents and adults, who may unknowingly transmit the infection to vulnerable infants.
The incidence among vaccinated children is significantly lower compared with unvaccinated populations, but outbreaks still occur. Infection rates remain considerable among older children and young adults due to waning immunity over time. Adults and older siblings often serve as reservoirs for transmission to infants who are either unvaccinated or incompletely vaccinated.
Prevention relies mainly on routine immunization, typically given in combination with diphtheria and tetanus vaccines during infancy and childhood, with booster doses later in life. Prophylactic antibiotics are recommended for close household contacts once a case is identified. Macrolides or trimethoprim-sulfamethoxazole are commonly used for this purpose.
The pathogenesis of pertussis involves colonization of the respiratory epithelium by the organism. Bordetella produces several toxins, including pertussis toxin and tracheal cytotoxin, which damage respiratory tissues and contribute to the characteristic prolonged cough. Inflammatory mediators such as bradykinin may also play a role in the persistent paroxysmal coughing spells.
After an incubation period of about 7–10 days, the disease classically progresses through three stages. The catarrhal phase resembles a mild upper respiratory infection with rhinorrhea, low-grade fever, and conjunctivitis. This is followed by the paroxysmal phase, characterized by severe bouts of coughing that may last several weeks. Finally, during the convalescent phase, coughing gradually improves over 1–2 weeks.
In young unvaccinated children, the hallmark finding is the “whoop,” a high-pitched inspiratory sound following a coughing fit. These episodes may be associated with cyanosis and vomiting. Adults and previously vaccinated individuals often present atypically with only a prolonged cough, which contributes to underdiagnosis and ongoing transmission.
Diagnosis is confirmed through culture or PCR testing of nasopharyngeal specimens, especially during the first two weeks of illness. Marked lymphocytosis may be present during the paroxysmal phase. Serologic testing demonstrating high antibody titers or a significant rise in antibodies can also support the diagnosis. Chest radiographs may show perihilar infiltrates, atelectasis, or consolidation in complicated cases.
Treatment is primarily supportive, especially in infants younger than one year, who are at greatest risk of severe disease. Antibiotics are mainly used to eradicate the organism and reduce transmission rather than shorten the duration of cough once the paroxysmal phase has begun. Macrolides such as azithromycin, clarithromycin, and erythromycin are the preferred agents. Trimethoprim-sulfamethoxazole is an alternative for patients who cannot tolerate macrolides.
Hospitalization may be required for infants, unvaccinated children, or patients with severe disease. Despite modern therapy, pertussis can lead to serious complications, particularly in infants, including pneumonia, apnea, seizures, encephalopathy, and death. Severe coughing can also cause subconjunctival hemorrhage, pneumothorax, rib fractures, rectal prolapse, and intracranial hemorrhage. Prognosis is generally excellent after recovery, although mortality remains highest among infants too young to be vaccinated.
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