What are the causes ?
Whooping cough is a highly contagious respiratory infection mainly caused by the bacterium Bordetella pertussis. It may also be caused by Bordetella parapertussis. The incidence of infections due to the latter agent varies considerably from one country to the next and is low in France.
How do the bacteria spread ?
Whooping cough is highly contagious: on average, one infected individual passes the disease on to 15 other people. Whooping cough is an airborne infection, spread by direct contact with infected people. In regions without a child vaccination program, transmission occurs among children. However, in regions like France where child vaccination programs have been in place for decades, whooping cough is now mainly transmitted from adults or adolescents to infants.
What are the symptoms?
Whooping cough is typically characterized by three phases:
(1) an incubation period which is initially asymptomatic, followed by rhinorrhea (runny nose) lasting approximately two weeks;
(2) a paroxysmal stage characterized by a persistent cough lasting over a week, in most cases without any fever. Bouts of coughing are combined with difficulty inhaling, and vomiting may occur after coughing fits. Infants may experience apnea, sometimes combined with bradycardia (slower than normal heart rate) or cyanosis (a bluish skin color) during coughing fits. In adolescents and adults, the symptoms are generally worse at night;
(3) the third stage of whooping cough is the convalescent stage, which may last for several weeks. In young children, the main complications include pneumonia and neurological disorders (seizures or encephalitis). In infants, whooping cough can be extremely serious or even fatal, causing respiratory failure or multiple organ failure.
How is infection diagnosed ?
As clinical characteristics may vary, especially in adolescents or adults depending on their immune status, laboratory diagnosis of whooping cough is vital so that the patient can be treated immediately with antibiotics, thereby preventing transmission as quickly as possible and protecting people in contact with the infected individual.
The only laboratory tests that are reimbursed under the French social security system are isolation of the bacterium (in culture) or detection of genetic material by PCR, from nasopharyngeal aspirates or swabs. Serology is not recommended as it is considered unreliable and has not been reimbursed since 2011.
What treatments are available?
The recommended antibiotics (most often macrolides) eliminate the bacteria from secretions, thereby reducing the risk of transmission. Antibiotic therapy is recommended for anyone in close contact with the patient who has not had a booster vaccination in the past five years, even if they are not yet experiencing any symptoms and irrespective of their age.
Hospitalization is strongly recommended for infants aged 0 to 3 months.
Since neither the bacterial infection nor the vaccine confer lifelong immunity, it is possible to contract the disease more than once.
How can infection be prevented?
Prevention is mainly based on vaccination.
Since 2022, vaccination during pregnancy has been recommended to protect newborn babies before they can be vaccinated themselves. Vaccination is recommended between 20 and 36 weeks of amenorrhea during each pregnancy.
In the absence of vaccination during pregnancy, postpartum vaccination is recommended for parents and anyone likely to come into close contact with the infant before the age of six months (the "cocooning" strategy).
Primary vaccination is given to children aged 2 months, 4 months and 11 months. A booster is given at age 6 and a further booster between the ages of 11 and 13. In adults, a booster is recommended at age 25 (a catch-up vaccine is recommended up to the age of 40).
As well as vaccination, antibiotics must be administered to patients with a confirmed case of whooping cough, and preventive antibiotics should be given to unvaccinated vulnerable individuals (even in the absence of symptoms) or those who have come into direct contact with a case of whooping cough.
As with all outbreaks of respiratory infections, masks are highly recommended, especially around vulnerable people, in health care facilities and care homes, in confined spaces and on public transport.
For more detailed and up-to-date information, please refer to the Santé publique France website (in French).
How many people are affected?
The incidence of whooping cough has fallen considerably in countries that have introduced routine vaccination programs for young children. The number of cases observed also decreased significantly during the COVID-19 pandemic, probably because of the general health and hygiene measures adopted during this period. According to Santé publique France, there are thought to be 40 million cases and 300,000 deaths each year worldwide.
Since early 2024, there has been a sharp rise in the number of cases of whooping cough caused by Bordetella pertussis in France. Between January and May 2024, more than 5,800 cases were recorded. Santé publique France has raised the alarm over this resurgence.
June 2024