Pertussis Rates Climbing in the United States

Pertussis cases in the United States have increased fourfold compared with the same time period last year, according to data from the Centers for Disease Control and Prevention (CDC). Reports from several states illustrate this trend, thought to be due to reduced immunity across the country.

The Alaska Department of Health issued a statement on its website about the significant increase in pertussis cases in the state during the summer, with 90 cases in July and 61 in August compared with 24 in June and a total of 26 cases in 2023. 

Similarly, the Florida Department of Health reported a pertussis increase in July 2024 that was higher than the June 2024 case count and also above the previous 5-year average.

Experts in these and other states suggest that several factors are driving the nationwide increase, including the fact that fewer people are consistently wearing masks. The mass masking during the COVID-19 pandemic caused a significant drop in pertussis, but the latest data suggest a return to prepandemic levels, and waning immunity likely plays a role as well.

Pertussis, also known as whooping cough, typically begins with symptoms similar to those of the common cold, including runny nose, sneezing, mild fever, and cough, according to the CDC. However, babies with whooping cough may experience trouble breathing rather than a cough. The coughing fits often associated with pertussis may not start until 2 weeks after the onset of other symptoms, according to the CDC. 

Those who have been vaccinated against pertussis can still become infected, but the risk is lower, and the illness, if it occurs, is likely to be milder. Complications such as apnea, pneumonia, and convulsions can occur in babies younger than 1 year, especially if they have not been vaccinated, according to the CDC.

Beyond Easing Pandemic Precautions

Many respiratory-based infections dipped during the COVID-19 pandemic, almost certainly from the multifactorial interventions of masking, distancing, and the general lack of comingling, said David J. Cennimo, MD, associate professor of medicine & pediatrics in the Division of Infectious Diseases at Rutgers New Jersey Medical School, Newark, New Jersey, in an interview.

The number of cases of many of these diseases returned to previous levels after COVID-19 restrictions were lifted, he said. 

“However, we know pertussis immunity wanes over time. Children get DTaP at 2, 4, 6, and 15 months, and a Tdap booster at 11-12 years old gets them to adulthood,” Cennimo said. Adults should be getting a Tdap every 10 years, he added. 

The latest available CDC data indicate that Tdap vaccine coverage in adults is approximately 40%, which means that there may be a large number of susceptible people who can become infected and propagate to others, said Cennimo.

Not Just the Young Ones

A recent pertussis outbreak among college students in Virginia highlighted the fact that the infection can affect all ages, and that the effectiveness of childhood vaccines may decrease over time. The majority of the recently diagnosed cases occurred in individuals who had been previously vaccinated, according to a press release from the Virginia Department of Health.

Clinical Clues

The initial stage of pertussis infection looks like a common cold with symptoms of upper respiratory infection, Cennimo told Medscape Medical News. “Unless there is reason to suspect pertussis exposure, it would almost certainly be missed,” he noted.

The characteristic barking/seal-like cough is mostly seen in children, said Cennimo. Adults and children can experience coughing fits that can lead to shortness of breath and/or vomiting, which would raise suspicion for pertussis, but is not universally present, he said. The convalescent stage of pertussis can be prolonged and is characterized by chronic coughing. “In the past, pertussis had been called the 100-day cough,” and at that point, treatment is ineffective, Cennimo said.

In clinical practice, “I advise everyone to get the Tdap vaccine every 10 years,” and remember that the “Td” is the every 10-year tetanus shot as well, Cennimo told Medscape Medical News. Reassure patients that the Tdap can be given with other vaccines, he said, and remind patients that, as with any of the respiratory illnesses, they should stay home if sick, cover a cough, consider wearing a mask in public, and wash hands frequently, he said. 

Cennimo had no financial conflicts to disclose.