Whooping cough, or the “100-day cough,” is a worldwide highly contagious disease caused by the Bordetella pertussis bacterium. Other species such as B. parapertussis and B. holmesii can cause similar but milder clinical conditions. Despite high vaccination coverage, pertussis remains a significant public health issue, particularly among young children. In recent years, the number of reported pertussis cases in adults and children has increased, according to the European Centre for Disease Prevention and Control (ECDC) (151,000 global cases in 2018, including 35,627 in Europe), with epidemic peaks occurring every 2–5 years. Currently, the disease prevalence is still likely underestimated.
What Is Whooping Cough and Why Is It Called the “100-Day Cough. Recommended Antibiotics for the Treatment of Pertussis in Pediatrics
When Do Children and Adults Get Whooping Cough?
There is no specific seasonality for pertussis. The rise in cases is partly due to waning vaccine protection, the availability of better diagnostic methods, and the increased awareness of the disease. Moreover, atypical presentations in adolescents and adults delay diagnosis and treatment, facilitating the spread of infection.
How Is Pertussis Transmitted?
Pertussis is extremely contagious and spreads through respiratory droplets released by coughing or sneezing. The primary sources of infection are asymptomatic or mildly symptomatic adolescents and adults (typically presenting with an isolated, persistent cough lasting more than three weeks) who are in close contact with children. Numerous toxins and virulence factors produced by the bacteria enable strong adhesion to the respiratory epithelium, causing mucosal damage that supports bacterial replication and symptom development.
Symptoms of Pertussis: How to Recognize It?
The incubation period of pertussis can be up to 4 weeks (typically 7–10 days). The illness progresses through three stages:
- the catarrhal phase;
- the paroxysmal phase;
- and the convalescent phase.
Catarrhal Phase (1–3 weeks)
presents with mild symptoms often indistinguishable from a common viral infection, such as nasal congestion, serous rhinitis, sneezing, tearing, slight dry cough, general discomfort, and low-grade fever (which may be absent).
Paroxysmal Phase (2–3 weeks)
is characterized by intense, rapid, violent coughing fits that last several minutes, often accompanied by inspiratory whoop, cyanosis, post-tussive vomiting, increased mucus and saliva production, and difficulty breathing. Triggers include crying, laughing, or swallowing, with attacks occurring mainly at night.
Final stage
Finally, during the Convalescent Phase symptoms gradually decrease, with a mild, less frequent, dry cough which can persist for 6–8 weeks.
The severity of the Pertussis depends on age and immune status.
Vaccinated adults and children usually experience milder symptoms, i.e. isolated prolonged cough. On the contrary, immunocompromised individuals and unvaccinated children—especially infants—are at greater risk of severe complications such as apnea, pneumonia, respiratory failure, seizures, and severe hyperleukocytosis, which can lead to pulmonary hypertension and even death, especially in newborns. Children are also frequently co-infected with respiratory viruses like Respiratory Sincitial Virus (RSV), influenza A, rhinovirus, or bocavirus.
Diagnosing, Treatment and Antibiotics of the Pertussis
Diagnosing and Treatment of the Whooping Cough
Given the high transmissibility, early diagnosis is essential to prevent further spread. Clinical suspicion alone is enough to initiate treatment: lab tests, although useful for public health purposes, should not delay therapy. Lab diagnosis can be done via nasopharyngeal swab (bacterial culture or PCR) or blood sample (serology). PCR is sensitive within three weeks of symptom onset, even in asymptomatic contacts, though false positives are possible. The diagnostic gold standard is bacterial culture, which requires specific media and 7–15 days to grow visible colonies. Cultures may be falsely negative if symptoms started long ago or antibiotics have already been started. Blood tests can measure anti-pertussis IgA (indicative of current or recent infection) and IgG (indicative of prior exposure or ongoing infection if IgA is also elevated).
What to Do in Case of Pertussis: Antibiotic Treatment
Treatment is based on antibiotic therapy (Table 1), which is most effective in reducing symptoms and transmission risk when started early (ideally within three weeks of symptom onset, during the catarrhal phase). In case of complications, supportive care including IV fluids or ventilation may be needed. In children with white blood cell counts above 10^5 cells/mm³ and pulmonary hypertension, plasmapheresis may be required. Unfortunately, the hallmark cough of pertussis in children has no specific remedy. Topical or systemic corticosteroids, bronchodilators, antitussive syrups, or antihistamines are not recommended, as their effectiveness has not been proven.
Recommended Antibiotics for the Treatment of Pertussis in Pediatrics
| Table 1. | |
| Azithromycin | 0-6 months of age: 10 mg/kg once daily for 5 days > 6 months of age: 10 mg/kg once on Day 1, then 5 mg/kg once daily from Day 2 to Day 5 |
| Clarithromycin | > 1 month of age: 15 mg/kg/die divided into two doses for 7 days |
| Trimetoprim +sulfamethoxazole* | > 2 months of age: 8 mg/kg/die of trimetoprim e 40 mg/kg/die of sulfamethoxazole every 12 hours for 14 days |
| * Alternative to macrolides if not tolerated. Do not administer to infants under 2 months of age or during pregnancy. | |
So when does pertussis go away?
Patients are no longer contagious after starting antibiotics. Symptoms gradually improve after about three weeks, but can last even 2–3 months, which is why pertussis is called the “100-day cough.”
Post-Exposure Prophylaxis
Close contacts include household members, healthcare workers, or anyone exposed to respiratory secretions or in confined spaces with a symptomatic patient for more than one hour at a distance of less than one meter. Up to 90% of household contacts and 50–80% of school contacts can quickly become infected. Therefore, it is essential—along with hand hygiene and prompt isolation of the infected person—to prevent further spread. Post-exposure antibiotic prophylaxis for close contacts (regardless of vaccination status) follows the same treatment protocol.
How Long Does the Pertussis Vaccine Last?
Italy’s 2023–2025 National Vaccination Plan includes three doses of whole-cell pertussis vaccine (DTaP) as part of the hexavalent vaccine in the first year of life (at 3, 5, and 11 months), with boosters at 5–6 and 12 years of age. After that, a Tdap booster (acellular vaccine for adults) is recommended every 10 years.
Vaccination for Whooping Cough During Pregnancy
There are no risks associated with receiving the pertussis vaccine during pregnancy. Recent pertussis cases in newborns in Italy highlight the importance of maternal vaccination with the acellular vaccine, ideally between weeks 27 and 36 of pregnancy. This strategy transfers protective antibodies to the baby through the placenta, reducing the risk of infection and severe outcomes during the most vulnerable early months of life.
Recommended Antibiotics for the Treatment of Pertussis in Pediatrics
| Table 1. Recommended Antibiotics for the Treatment of Pertussis in Pediatrics | |
| Azithromycin | 0-6 months of age: 10 mg/kg once daily for 5 days > 6 months of age: 10 mg/kg once on Day 1, then 5 mg/kg once daily from Day 2 to Day 5 |
| Clarithromycin | > 1 month of age: 15 mg/kg/die divided into two doses for 7 days |
| Trimetoprim +sulfamethoxazole* | > 2 months of age: 8 mg/kg/die of trimetoprim e 40 mg/kg/die of sulfamethoxazole every 12 hours for 14 days |
| * Alternative to macrolides if not tolerated. Do not administer to infants under 2 months of age or during pregnancy. | |
Action Plan of treatment for Pertussis in pediatrics:
- Vaccinate children and adults
- Avoid contact with contagious individuals
- Contact a doctor
- Get tested
- Start treatment in suspected cases
Checklist:
- Ensure your child receives all scheduled pertussis vaccinations
- Get booster shots during adolescence and adulthood
- Receive an extra booster dose if pregnant
- Avoid contact with sick individuals until they are no longer contagious (usually one week after starting antibiotics)
- If you or your child have suspected pertussis, contact your doctor for testing and prompt treatment.
Author: Beatrice Andrenacci, MD, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan (MI), Italy, SC Pediatric Pulmonology and Pediatric Infectious Disease
References
- Decker MD, Edwards KM. Pertussis (Whooping Cough). J Infect Dis. 2021;224(12 Suppl 2):S310-S320. doi:10.1093/infdis/jiaa469
- Kilgore PE, Salim AM, Zervos MJ, Schmitt HJ. Pertussis: Microbiology, Disease, Treatment, and Prevention. Clin Microbiol Rev. 2016;29(3):449-486. doi:10.1128/CMR.00083-15
- https://www.epicentro.iss.it/pertosse/epidemiologia
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