Given the rise in cases in Mexico, it is essential to administer the hexavalent vaccine and the necessary boosters to children promptly to immunize at-risk adults
Claudia Villalobos
At the first sign of cold-like symptoms in infants under six months, parents should seek medical attention to rule out infection by the gram-negative bacterium Bordetella pertussis, the cause of whooping cough. The disease begins insidiously, initially resembling a mild cold, making it easy to mistake for a minor respiratory infection. However, if left untreated, it can lead to serious complications and even fatal outcomes.
To prevent further outbreaks of this disease in Mexico, it is crucial to remain vigilant and protect the most vulnerable populations.
Dr. Silvia Giono Cerezo, a microbiologist at the Instituto Politécnico Nacional (IPN), explained that infants under six months are highly susceptible to infection. Therefore, she recommends that parents provide timely medical care, ensuring appropriate medication and close monitoring of symptoms to prevent complications.
The expert in infectious disease studies, assigned to the National School of Biological Sciences (ENCB), explained that whooping cough progresses through three stages: catarrhal, paroxysmal, and convalescent. Its approximate duration is three months, which is why it is known in Japan as the 100-day disease.
Since initial symptoms (catarrhal period) are non-specific and similar to a viral upper respiratory tract infection, special attention must be paid to their evaluation. The preferred diagnostic method is culture and/or polymerase chain reaction (PCR) testing of a nasopharyngeal aspirate or swab.
Dr. Giono Cerezo stated that early diagnosis is ideal because the bacterium can be isolated in a special culture medium in its initial stage. Later on, it becomes more difficult to recover and cultivate the microorganism. She explained that the severity of the infection is because, in infants under one-year-old, symptoms are not very clear. At the beginning (catarrhal stage), the disease typically presents as a runny nose (rhinorrhea) with a mild cough.
At the first sign of this acute respiratory infection, if whooping cough is suspected in its early stage—when it is known to be highly contagious and exclusively human-borne—she urged parents to remain alert and take the child to a healthcare professional. The doctor can prescribe appropriate antibiotic treatment, following a confirmed diagnosis via culture or PCR and ruling out a common cold. She also emphasized the importance of avoiding self-medication.
The second stage, known as the paroxysmal stage, is severe because the cough, which mainly occurs at night, becomes so persistent that infants may turn purple, suffer seizures, and emit a high-pitched wheezing sound. Infants are at higher risk of death and complications, as their breathing may temporarily stop during coughing fits.
Dr. Silvia Giono stated that this respiratory condition may lead to complications such as pneumonia, caused by a secondary infection different from that generated by Bordetella pertussis.
She noted that during the paroxysmal stage, it is also possible for blood sugar levels to drop, and an increase in white blood cells (lymphocytosis) may be observed.
In the final phase, known as the convalescent stage, symptoms gradually diminish, but they persist for one to two months, especially coughing, which intensifies with physical exertion or other illnesses.
Whooping cough is transmitted directly from person to person via airborne droplets expelled when someone talks, coughs, sneezes, or breathes (Pflüger’s droplets).
As a vaccine-preventable disease, Dr. Giono Cerezo stated that, given the increase in cases, it is essential to administer the hexavalent vaccine and the respective boosters to children, as well as to vaccinate unprotected adults.
The vaccination schedule establishes the application of four doses of the hexavalent vaccine (which protects against diphtheria, whooping cough, Haemophilus influenzae type b, tetanus, poliomyelitis, and hepatitis B) at two, four, six, and 18 months of age, as well as a booster at four years old. The IPN researcher urged that these vaccines be administered on time to achieve immunity and thus reduce the number of cases of the disease.
The pathogenicity of Bordetella pertussis is associated with various virulence factors that are critical for invasion and disease production.
In this regard, the IPN researcher explained that the bacterium responsible for whooping cough produces a very potent toxin (pertussis toxin), along with other components that allow it to adhere to the respiratory epithelium, causing the symptoms of the paroxysmal stage. Additionally, it damages the respiratory cilia (tiny hair-like structures that line the respiratory tract), facilitating bacterial adhesion.
INSTITUTO POLITÉCNICO NACIONAL
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