More than 25,000 cases of whooping cough have been recorded in the U.S. so far this year, updated federal data shows.

This marks the second year in a row with higher than usual cases, according to data from the Centers for Disease Control and Prevention (CDC). At the same time this year, around 33,000 cases reported.

Cases are well above pre-pandemic levels. In 2019, about 18,600 whooping cough cases were recorded, CDC data shows.

Excluding last year, the last time whooping cough cases were this high was in 2014 when more than 32,900 cases were recorded, according to the CDC. 

Meanwhile, doctors’ visits for pertussis are trending down from the peak seen in winter of last year but still remain elevated compared to years prior, data from Epic Research shows. 

Whooping cough, also known as pertussis, is a very contagious respiratory illness caused by a type of bacteria called Bordetella pertussis, according to the CDC.

These bacteria attach to the cilia in the upper respiratory system and release toxins. The toxins damage the cilia — tiny, hair-like structures found on the surface of cells — and cause the upper airways to swell.

The illness is especially dangerous for babies and young children, and several deaths have been recorded this year, including in Louisiana and Washington state.

Whooping cough is spread from person-to-person through coughing and sneezing. Infected people can be contagious for weeks without knowing they have whooping cough.

Early symptoms often resemble a common cold — runny nose, cough and low-grade fever — and typically last for one to two weeks. Symptoms, however, can progress to rapid, violent cough coughing fits that can last up to 12 weeks.

Whooping cough can be treated with antibiotics and receiving treatment early can reduce the severity of the infection. Most whooping cough symptoms can be managed at home, according to the CDC.

A vaccine for whooping cough was introduced in the late 1940s and the number of cases each year has since dropped dramatically, decreasing more than 90% compared to the pre-vaccine era.

Before the vaccine, there were an estimated 200,000 cases annually among children and up to 9,000 children died annually, according to the CDC.

There are two types of vaccines used today to protect against whooping cough: diphtheria, tetanus, and pertussis (DTaP) vaccine for babies and children younger age 7 and tetanus, diphtheria, and pertussis (Tdap) vaccines for children aged 7 and older, adults and pregnant women.

However, vaccination rates for whooping cough have steadily dropped in recent year, CDC data shows.

Only 92.1% of kindergarteners were vaccinated against whooping cough during the 2024-25 school year, compared to about 95% pre-pandemic, during the 2019-2020 school year.