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Infant pertussis: who was the source?
Kristine M Bisgard1, F Brian Pascual, Kristen R Ehresmann
1Bacterial Vaccine Preventable Diseases Branch, National Immunization Program, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Insights
Family members are the primary source of pertussis (whooping cough) for infants. Identifying these sources is key to preventing the disease in vulnerable babies.
Area of Science:
- Epidemiology
- Infectious Disease Transmission
- Public Health
Background:
- Pertussis (whooping cough) incidence increased in the US during the 1990s, with infants under one year facing the highest risk.
- Reported pertussis cases in infants under one year of age showed significant variation across four states with Enhanced Pertussis Surveillance.
Purpose of the Study:
- To investigate the epidemiology of reported pertussis cases in infants.
- To determine the primary source of pertussis transmission to infants.
Main Methods:
- Examined pertussis case data from four states utilizing Enhanced Pertussis Surveillance.
- Defined the source of pertussis as an individual with acute cough illness in contact with the infant 7-20 days prior to symptom onset.
- Interviewed family members of reported case-infants to identify the source of infection.
Main Results:
- Family members were identified as the source of pertussis for 43% of case-infants with an identified source.
- Mothers were the source for 32% of these infants, and other family members for 43%.
- Individuals aged 30 years and older constituted the largest age group (35%) among identified pertussis sources.
Conclusions:
- Family members are the predominant source of pertussis transmission to infants.
- Variations in reported incidence may stem from differences in healthcare provider awareness, diagnostic capabilities, and case classification.
- Understanding transmission dynamics is crucial for developing effective prevention strategies for infants.
Background:
In the United States in the 1990s, the incidence of reported pertussis in adults, adolescents and infants increased; infants younger than 1 year of age had the highest reported incidence.
Methods:
In 4 states with Enhanced Pertussis Surveillance, we examined the epidemiology of reported pertussis cases to determine the source of pertussis among infants. A source was defined as a person with an acute cough illness who had contact with the case-infant 7-20 days before the infant's onset of cough.
Results:
The average annual pertussis incidence per 100,000 infants younger than 1 year of age varied by state: 22.9 in Georgia; 42.1 in Illinois; 93.0 in Minnesota; and 35.8 in Massachusetts. Family members of 616 (80%) of 774 reported case-infants were interviewed; a source was identified for 264 (43%) of the 616 case-infants. Among the 264 case-infants, mothers were the source for 84 (32%) and another family member was the source for 113 (43%). Of the 219 source-persons with known age, 38 (17%) were age 0-4 years, 16 (7%) were age 5-9 years, 43 (20%) were age 10-19 years, 45 (21%) were age 20-29 years and 77 (35%) were age > or =30 years.
Conclusions:
The variation in reported pertussis incidence in the 4 states might have resulted from differences in awareness of pertussis among health care providers, diagnostic capacity and case classification. Among case-infants with an identifiable source, family members (at any age) were the main source of pertussis. Understanding the source of pertussis transmission to infants may provide new approaches to prevent pertussis in the most vulnerable infants.
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