Pertussis

Pertussis, commonly known as whooping cough or the '100-day cough,' is a highly contagious bacterial respiratory infection caused exclusively by Bordetella pertussis. Humans serve as the sole natural host species for this pathogen. The disease is classified under ICD-10 code A37 and ICD-11 code CA01, and it represents one of the most prevalent vaccine-preventable diseases affecting the respiratory tract worldwide.

The clinical presentation of pertussis typically begins with mild respiratory symptoms resembling the common cold, including runny nose, fever, and a mild cough, which appear after an incubation period averaging 7-14 days (range 6-42 days). In typical cases, this initial phase progresses over one to two weeks into severe paroxysmal coughing fits that may last 10 or more weeks, giving rise to the colloquial designation as the '100-day cough.' Following coughing paroxysms, patients may produce a characteristic high-pitched whooping sound or gasp during inspiration. The violent nature of the cough can lead to complications including fatigue, vomiting, rib fractures, subconjunctival hemorrhages, urinary incontinence, and in rare cases, pneumothorax or vertebral artery dissection. Pneumonia represents a relatively common complication, while seizures and encephalopathy occur rarely. Infants under one year of age may present atypically with little or no cough and instead experience apneic episodes during which they cannot breathe. Disease can occur in previously vaccinated individuals, though symptoms are typically milder than in unvaccinated cases.

Pertussis demonstrates a worldwide distribution, with global case counts exceeding 151,000 reported cases in 2018. The disease epidemiology exhibits cyclical patterns with periodic outbreaks, and transmission occurs efficiently in close-contact settings including households, childcare facilities, and healthcare environments. While vaccination has substantially reduced disease burden, pertussis remains endemic in many regions with fluctuating incidence rates influenced by vaccine coverage levels, waning immunity in adolescents and adults, and the emergence of antigenic variants of B. pertussis. The disease disproportionately affects infants, who experience the highest rates of severe disease, hospitalization, and mortality, making pertussis a significant cause of disease and death in this vulnerable age group globally.

Pertussis is transmitted through airborne droplets generated by coughing or sneezing from infected individuals, making close person-to-person contact the primary route of spread. The bacterium B. pertussis is highly contagious, with secondary attack rates among susceptible close contacts approaching 80-100% in susceptible populations. Individuals remain infectious from the onset of symptoms until approximately three weeks into the coughing phase, though this period may be shortened by appropriate antibiotic treatment. As humans are the only natural host species, transmission dynamics are entirely person-to-person, with no animal reservoir currently recognized in the natural disease cycle.

Infants represent the highest-risk population for severe pertussis outcomes, including hospitalization and death, particularly those too young to have completed the primary vaccination series. Unvaccinated or incompletely vaccinated children remain at elevated risk for severe disease. Pregnant women in their third trimester benefit from vaccination to protect newborns through passive antibody transfer. Adolescents and adults may experience milder disease but can transmit infection to vulnerable infants in household and close-contact settings.

Immunization with pertussis-containing vaccines remains the cornerstone of prevention strategies. The World Health Organization recommends administration of the first dose as early as 6 weeks of age, with subsequent doses given at 4-8 week intervals (typically at 10-14 weeks and 14-18 weeks) to complete the three-dose primary series. A booster dose is recommended during the second year of life, and additional booster doses may be warranted later in life based on local epidemiological considerations. Maternal vaccination during pregnancy has proven effective in protecting infants too young to receive their own vaccinations. Global coverage with three doses of DTP-containing vaccine reached 86% of the target population in 2018, though coverage gaps persist in certain regions and population subgroups.

Pertussis surveillance should account for the disease's characteristic prolonged clinical course and the potential for milder presentations in vaccinated individuals, which may affect case detection and reporting completeness. Laboratory confirmation through nasopharyngeal sampling with culture or polymerase chain reaction testing is the standard diagnostic approach. The three-week infectious period beginning with symptom onset has implications for isolation protocols and contact tracing activities. Surveillance systems should monitor coverage of both primary vaccination series and booster doses across age groups, as waning immunity contributes to ongoing transmission in adolescent and adult populations who serve as reservoirs for infant infection.

1. 1 WHO Health Topics. Pertussis.
2. 2 WHO Fact Sheet. Detail.
3. 3 WHO Q&A. News.
4. 4 Wikidata. pertussis.
5. 5 Wikipedia. Whooping cough - Wikipedia.

ICD-10

A37

ICD-11

CA01

Total cases

1.4M

Total deaths

58

Peak month

2024-05

Coverage

4 reporting countries · 2000-01-01 → 2026-05-09