How CDC Tracks Pertussis, and What the Numbers Show

Pertussis is a nationally notifiable disease. CDC follows it through a national surveillance system, and in more depth through a partnership with several states. Reported cases have risen over the past few decades, and experts believe much of the disease still goes unrecognized and unreported.

How cases are reported

NNDSS is useful for following trends over time. Weekly case counts, current and past, are published in its infectious disease tables. Because reports lag and data must be checked, state and local health departments have the most current numbers. The case definition used for surveillance was last published by the Council of State and Territorial Epidemiologists in 2020.

Enhanced Pertussis Surveillance

CDC also works with seven states in the Emerging Infections Program network on Enhanced Pertussis Surveillance, which goes beyond what NNDSS collects. These sites:

• search more thoroughly for cases and collect more detail on each;
• gather bacterial isolates and specimens for further study at CDC;
• provide a base for special studies of pertussis.

The network also tracks other Bordetella species.

A century of pertussis

Before vaccines. In the 20th century pertussis was one of the most common childhood diseases and a major cause of child deaths in the United States. Before a vaccine was available in the 1940s, more than 200,000 cases were reported each year.

1940s to mid-1980s. Widespread vaccination of children began with the DTP vaccine (diphtheria, tetanus toxoid and whole-cell pertussis) in 1948. Since then, yearly cases have fallen by more than 90% compared with the pre-vaccine era.

Late 1980s to 2010s. Reports began to climb gradually in the 1980s, peaking in 2012 at 48,277 cases. Likely reasons include:

• better recognition of pertussis by health care providers;
• wider access to and use of laboratory tests;
• more surveillance and reporting to health departments;
• waning immunity from acellular pertussis vaccines, which fully replaced DTP in the childhood schedule in 1996.

Cases stayed high after 2012 until the COVID-19 pandemic began in 2020. CDC's historical chart marks the arrival of DTP (1948), DTaP (1992) and Tdap (2005).

2020s. Reported cases were lower than usual during and just after the pandemic, likely because measures such as masking and physical distancing also cut pertussis spread. In 2024 the country returned to the pre-pandemic pattern, in which more than 10,000 cases are typically reported a year:

• Preliminary data showed more than six times as many cases in 2024 as in 2023, and more than in 2019, before the pandemic.
• In 2025, preliminary counts stayed high compared with just before the pandemic, but cases had been trending down since a peak in November 2024.
• When CDC's page was captured, preliminary data showed fewer cases reported in 2026 than at the same point in 2025.

These figures are preliminary and will change as CDC finalizes them.

Infants are hit hardest

Babies under one year old face the greatest risk of serious illness and death, because their immune systems are still developing. They continue to have the highest reported rate of pertussis of any age group.

Antibiotic resistance

Reports of antibiotic-resistant Bordetella pertussis have so far been rare in the United States. Resistance to macrolides — a class of antibiotics commonly used to treat pertussis — is being reported more and more in other parts of the world, including Asia, Australia, Europe and South America. CDC monitors for resistance in the United States by testing isolates collected through Enhanced Pertussis Surveillance.

Where the data are

CDC publishes yearly pertussis surveillance reports — case counts and incidence by state and age, the DTaP vaccination history of cases, and deaths — with older reports held in the CDC Stacks library.

Sources

• Centers for Disease Control and Prevention: "Pertussis Surveillance and Trends."