The United States is grappling with a sustained and troubling resurgence of whooping cough (pertussis), a highly contagious respiratory infection once considered under control. Provisional data for 2025 reveals nearly 28,000 reported cases, marking the second consecutive year the national total has surpassed 25,000 infections. While this figure represents a decrease from 2024’s peak of 35,493 cases, it remains dramatically higher than pre-pandemic baselines. For context, only 7,063 cases were reported in 2023, making the current multi-year surge a significant public health alarm.
This pattern suggests we are not witnessing a simple, isolated outbreak but a fundamental shift in the disease’s epidemiology. The last time the U.S. saw numbers of this magnitude was prior to the widespread adoption of the acellular pertussis (aP) vaccine in the 1990s. The current crisis underscores a critical gap in population immunity and highlights vulnerabilities in our defense against vaccine-preventable diseases.
Decoding the Surge: More Than Just a Post-Pandemic Bounce
The simplistic explanation—that cases are rising because people are mixing more after the COVID-19 pandemic—fails to capture the full picture. While reduced social distancing plays a role, epidemiologists point to a confluence of deeper, more persistent factors:
- Waning Vaccine Immunity: The modern acellular pertussis vaccine (DTaP/Tdap), introduced to reduce side effects, does not confer lifelong protection like its whole-cell predecessor. Immunity from childhood DTaP shots begins to diminish significantly in early adolescence. Without the recommended Tdap booster, adolescents and adults become susceptible, often experiencing milder “cold-like” symptoms that go undiagnosed but allow them to unknowingly transmit the bacteria to vulnerable populations.
- The Transmission Reservoir: This creates a vast reservoir of contagious adolescents and adults. They act as a bridge, spreading the Bordetella pertussis bacteria to two critically at-risk groups: infants too young to be fully vaccinated and individuals who are immunocompromised.
- Diagnostic Awareness and Testing: Increased clinical suspicion and better access to PCR testing post-COVID may be identifying cases that were previously missed, contributing to the higher reported numbers. However, this alone cannot account for the fourfold increase from 2023 levels.
The Human Cost: Why Deaths Are Climbing
The most distressing metric is the climbing death toll, which disproportionately targets infants under six months of age. For these babies, who are too young to have completed the primary three-dose vaccine series, whooping cough is not just a bad cough; it is a life-threatening illness. Complications include:
- Apnea (Dangerous Pauses in Breathing): The classic “whoop” sound may be absent; instead, infants may turn blue from lack of oxygen.
- Pneumonia: A common and severe secondary bacterial infection.
- Encephalopathy: Brain swelling due to intense coughing or lack of oxygen, which can lead to seizures and permanent neurological damage.
Every adult case in a community represents a potential direct threat to the youngest and most vulnerable. This is why the strategy of “cocooning”—vaccinating all close contacts of a newborn, including parents, grandparents, and siblings—is considered a vital layer of protection.
A Path Forward: Beyond Basic Awareness
Addressing this surge requires moving beyond alarm and into actionable public health strategy. Key measures include:
- Booster Adherence: Ensuring adolescents receive their Tdap booster (typically at age 11-12) and that all adults receive a Tdap booster once, followed by a Td or Tdap booster every 10 years. Pregnant individuals should receive a Tdap dose during each pregnancy, ideally between 27 and 36 weeks of gestation, to pass protective antibodies directly to the fetus.
- Healthcare Provider Vigilance: Clinicians must consider pertussis in patients with a prolonged cough (lasting more than two weeks), even without the classic whoop, and test appropriately. Early diagnosis and treatment with antibiotics (like azithromycin) can reduce transmission.
- Community and Policy Action: Supporting policies that ensure easy access to vaccines for adults and promoting public awareness campaigns that frame vaccination not just as a personal choice, but as a communal responsibility to protect those who cannot protect themselves.
The 2025 data is a stark reminder that whooping cough never truly disappeared. The bacteria circulates continuously, and our collective immunity is a shield that requires regular maintenance. The surge in cases and deaths is a measurable consequence of gaps in that shield. Closing them is a matter of scientific knowledge, healthcare access, and societal commitment to the most fragile among us.
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