Whooping cough, medically known as pertussis, is caused by a specific type of bacteria called *Bordetella pertussis*. This bacterium is a tiny, rod-shaped, Gram-negative organism that primarily infects the respiratory tract. The infection spreads from person to person through airborne droplets released when an infected individual coughs or sneezes. Because it is highly contagious, pertussis can quickly move through communities, especially affecting those who are unvaccinated or have weakened immune systems.
The process begins when *Bordetella pertussis* bacteria enter the nose and throat of a susceptible person. A key factor in the bacteria’s ability to cause disease is its capacity to colonize the nasal passages and upper respiratory tract. Recent research has uncovered that the bacteria produce a special complex carbohydrate molecule, known as a glycan, which helps them stick to the lining of the nose and throat. This glycan is crucial because it allows the bacteria to establish themselves firmly, resist being cleared by the body’s natural defenses, and multiply. Without this glycan, the bacteria would struggle to maintain infection or spread to others.
Once the bacteria have colonized the respiratory tract, they begin producing toxins that cause the symptoms of whooping cough. These toxins damage the cells lining the airways, leading to inflammation and swelling. The damage makes it difficult for the lungs and airways to clear mucus effectively. As a result, the infected person experiences intense coughing fits, which are the hallmark of pertussis. These coughing episodes can be so severe that they cause the characteristic “whooping” sound when the person gasps for air after a coughing spell. In infants and young children, this can be particularly dangerous, sometimes leading to choking, difficulty breathing, or even suffocation.
The bacteria’s toxins also interfere with the immune system, helping *Bordetella pertussis* evade immune responses and persist longer in the respiratory tract. This ability to avoid immune clearance means that even vaccinated individuals can sometimes carry and spread the bacteria, although vaccination greatly reduces the severity of the disease.
Historically, whooping cough was a major cause of childhood illness and death worldwide. Before vaccines were developed, outbreaks were common and often deadly, especially for infants. The introduction of the pertussis vaccine in the mid-20th century dramatically reduced the number of cases and deaths. However, despite widespread vaccination, pertussis has not been eradicated. The bacteria’s ability to colonize the nose and evade immune responses, combined with waning immunity over time, means that outbreaks still occur, particularly among infants too young to be fully vaccinated and older individuals whose immunity has decreased.
The disease typically starts with mild cold-like symptoms, such as a runny nose, sneezing, and a mild cough. After one to two weeks, the cough worsens into severe, uncontrollable coughing fits. These fits can last for several weeks and are often followed by the distinctive whooping sound. In some cases, especially in infants, complications such as pneumonia, seizures, or brain inflammation (encephalopathy) can occur, which can be life-threatening.
The spread of pertussis is facilitated by close contact in crowded environments like schools and daycare centers. Because the bacteria spread through droplets, even brief exposure to an infected person can lead to transmission. This is why vaccination, good hygiene, and early diagnosis are critical in controlling outbreaks.
In summary, whooping cough is caused by the bacterium *Bordetella pertussis*, which infects the respiratory tract by attaching to the nasal and throat lining using a special glycan molecule. It produces toxins that damage the airways, leading to severe coughing fits and the characteristic whooping sound. Despite vaccination efforts, the bacteria’s ability to persist and spread means pertussis remains a public health concern, especially for vulnerable populations like infants and the elderly.
