By Katia Hetter, CNN
(CNN) — Cases of whooping cough are climbing across the country this year, with about 6,600 already documented — nearly four times the number at the same point last year.
In 2024, there were more than 35,000 cases of whooping cough in the United States, the highest in more than a decade. Ten people died, including six babies less than 1 year old.
Given the rise in cases, I wanted to know what causes whooping cough, how it spreads and what the symptoms are. What vaccine is recommended to prevent it, and who should get it? Why do cases appear to be surging? And what should people who are concerned about whooping cough do protect themselves and others?
To guide us through these questions, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and clinical associate professor at George Washington University. She previously was Baltimore’s health commissioner.
CNN: What causes whooping cough?
Dr. Leana Wen: Whooping cough, also called pertussis, is a highly contagious respiratory illness caused by the bacteria Bordetella pertussis. These bacteria are spread from person to person. If someone infected with pertussis coughs or sneezes, tiny droplets are released that contain the bacteria. People nearby can become infected by breathing in the droplets. The bacteria can also be spread through prolonged close contact when people share the same breathing space — for instance, when infected people hold a baby.
CNN: What are the symptoms?
Wen: The symptoms generally start seven to 10 days following infection. Initially, an infected person develops symptoms similar to a cold and other mild respiratory infections, such as a low-grade fever, runny nose and cough. The cough often then progresses to a severe hacking cough that is characterized by violent coughing fits.
During these coughing fits, people may make a high-pitched “whoop” when they try to take breaths after they cough, hence the name whooping cough. The fits may be so severe that they vomit during or afterward. Many struggle to sleep as a result. Some may have trouble breathing, and patients have been known to break their ribs due to the severity of the force associated with coughing.
Pertussis is especially dangerous in infants. Globally, it is a significant cause of disease and death in infancy, according to the World Health Organization. About 1 in 3 babies younger than 1 year old infected with pertussis will need care in the hospital, according to the US Centers for Disease Control and Prevention. CDC statistics also indicate that about 1 in 5 of those hospitalized develop pneumonia, 1 in 50 have convulsions, and about 1 in 100 will die from their complications.
In addition, there are people with preexisting health conditions that may be exacerbated by pertussis. These include those who are immunocompromised or have moderate to severe asthma.
CNN: How long does recovery take? Can anything speed it up?
Wen: Length of time to recover depends on the individual. Coughing fits typically last between one and six weeks, but they can persist for as long as 10 weeks.
The treatment for pertussis is antibiotics. There are a variety of common antibiotics that are effective against pertussis, including azithromycin, clarithromycin and erythromycin. The earlier the treatment begins, the better the prognosis. Early treatment has been shown to reduce severity and the time to recover.
CNN: How is pertussis diagnosed? How long is someone contagious?
Wen: In some patients, the diagnosis can be made simply by hearing the characteristic cough. Others who are a bit more subtle will require testing via a nose and throat swab.
People infected with pertussis can spread the bacteria from the time their symptoms start until at least two weeks after coughing begins. Many cases of pertussis may be spread by people who think they have a run-of-the-mill virus before their severe coughing fits begin. Early use of antibiotics can shorten the time someone is contagious.
CNN: What vaccine is recommended to prevent it? At what ages should it be given?
Wen: There are two types of combination vaccines that include protection against pertussis, the DTaP vaccine and Tdap. These vaccinations include protection against tetanus (the “T” in each name) and diphtheria (the “D” and “d” in those names).
The DTaP series is five doses of the vaccine given at 2 months, 4 months and 6 months old, then 15 months through 18 months old, then 4 years through 6 years old, according to the CDC’s recommended immunization schedule. Tdap is then recommended for all adolescents, with the preferred age of administration being 11 to 12 years old.
Adults who never received Tdap should receive a single dose. To maintain protection, all adults should also receive a booster every 10 years. And pregnant women are recommended one dose of Tdap during a pregnancy to be given during gestational weeks 27 through 36 to convey some antibodies to their baby. Getting the vaccines reduces the likelihood of contracting pertussis as well as the severity of the disease if one were to get it.
CNN: Why are pertussis cases increasing?
Wen: The exact cause is not known, though there are some hypotheses. One is related to the Covid-19 pandemic: More people were wearing masks, isolating and taking precautions that reduced transmission of all respiratory illnesses. As a result, there were fewer pertussis cases then, with a rebound once these precautions stopped. Moreover, vaccination rates for DTaP along with other childhood immunizations have been declining. This is an unfortunate development. People should be reminded that during the early part of the 20th century, before widespread availability of the pertussis vaccine, pertussis was a major cause of childhood mortality in the US.
CNN: What should parents and people concerned about whooping cough do protect themselves?
Wen: Completing the DTaP series is important, as is receiving the Tdap vaccine for those who are eligible. Individuals with symptoms of pertussis should get tested so that they can know if they have pertussis and prevent spread to others.
People should also know that the likelihood of spread within a household is high. In addition to good handwashing and the limiting of contact with infected people, the CDC recommends that everyone who shares a household with someone who has pertussis, even if they don’t have symptoms, should get antibiotics within 21 days of the beginning of the cough in that initial person.
This method of receiving antibiotics after exposure, known as post-exposure prophylaxis, can help reduce their chance of contracting pertussis. In addition, the CDC supports providing antibiotics to people at high risk of severe infection within 21 days of exposure to someone who has pertussis.
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