Critical Pertussis Situation in the Americas
The Pan American Health Organization (PAHO) and the World Health Organization (WHO) released an epidemiological update for year-end, revealing a steep rise in pertussis (whooping cough) cases across the Americas. The report links this resurgence to low vaccination coverage in several countries, triggering an unprecedented outbreak including Mexico.
Pertussis is a respiratory infection characterized by paroxysmal cough, sudden, violent, and uncontrollable bouts of coughing. The most common causative agent is Bordetella pertussis, though it has also been associated with Bordetella parapertussis in human cases. Pertussis remains a significant cause of morbidity and mortality in infants under two years old.
Authorities have declared, “Globally, pertussis has skyrocketed.” In 2024, 977,000 cases were reported to WHO, a fivefold increase from the previous year. The Americas region experienced a drastic rise, going from 11,202 cases in 2023 to 66,184 cases in 2024.
They highlight the primary risk factor as weakened herd immunity, as regional DTP3 (difteria, tetanus, and pertussis) third-dose coverage hit a two-decade low of 81% in 2021 and, despite recovery to 87% in 2024, the PAHO emphasizes “significant disparities between countries.”
Historical Outbreak in Mexico
Mexico is at the epicenter of the regional alert due to insufficient vaccination coverage and a significant increase in pertussis cases’ morbidity and mortality in 2025.
DTP3 third-dose coverage data, crucial for pertussis protection in childhood, show a decline preceding the current outbreak: DTP3 coverage in 2024 was 78%, equaling the country’s historical minimum and remaining below the 80% threshold, exposing many children to the disease. In contrast, DTP1 coverage in 2024 was 83%.
The consequence of this low protection materialized in a public health alert during 2025. Between the Epidemiological Week (SE) 1 and SE 48 of 2025, Mexico reported 1,561 confirmed pertussis cases and 71 associated deaths. The cumulative incidence was 1.17 cases per 100,000 inhabitants.
The figures for 2025 surpass those recorded in the past decade in the country, confirming the outbreak’s magnitude. Cases have been registered in 31 of the 32 federal entities.
The most affected federal entities include Mexico City, leading the list with 154 confirmed cases and ten deaths. Close behind are Chihuahua (146 cases, seven deaths), Nuevo León (141 cases, seven deaths), and Aguascalientes (102 cases, including two deaths).
The under-one-year group concentrates the largest proportion of affected individuals, with 507 cases (32.5%) out of the total, followed by the one to four-year group with 140 cases (9%). The sex distribution shows a higher incidence among women, who represent 57% of the cases (895 cases).
Vaccination: The Most Effective Measure for Control
The pertussis resurgence underscores the importance of vaccination as the most effective tool for preventing the disease, especially in its severe and fatal forms affecting predominantly infants.
According to the WHO, the combined DTP (or its variants DTaP, Tdap) vaccine’s proven success “has historically been crucial, drastically reducing pertussis cases worldwide.” Protection is most effective when the population maintains high and complete vaccination coverage, which in Mexico includes doses at two, four, six months, and a booster at four years old.
The PAHO and WHO also recommend Tdap vaccination for pregnant women (ideally in the third trimester) to transfer antibodies to newborns, a group too young to complete their own immunization and most vulnerable to complications.
Alternatively, pertussis treatment focuses on administering antibiotics (mainly macrolides like azithromycin) to kill Bordetella pertussis, reduce contagiousness, and, if administered early, lessen the disease’s severity.
For severely ill infants and young children, especially those with respiratory difficulties, dehydration, or apnea, hospitalization with isolation is necessary. Hospital care focuses on keeping respiratory tracts clear, administering oxygen, and preventing dehydration with intravenous fluids. Over-the-counter cough medicines or suppressants are not considered effective for pertussis.
Today, Mexican health authorities face the urgent challenge of intensifying immunization campaigns and epidemiological surveillance to contain the current outbreak, reverse the decline in DTP3 coverage, and protect the infant population.
