Seasonal influences on pertussis

Area of Science:

• Epidemiology
• Infectious Disease Dynamics
• Public Health Surveillance

Background:

• Pertussis (whooping cough) incidence and seasonal patterns have evolved significantly over the past four decades in England and Wales.
• Understanding these shifts is crucial for effective public health interventions and disease control strategies.

Purpose of the Study:

• To analyze changes in the absolute levels and seasonal patterns of pertussis over the last 40 years.
• To investigate the underlying transmission dynamics and identify factors influencing pertussis seasonality.
• To explore the potential impact of vaccination trends on observed epidemiological patterns.

Main Methods:

• Analysis of reported pertussis incidence data spanning four decades in England and Wales.
• Examination of temporal trends and seasonal variations in epidemic peaks.
• Correlation of seasonal patterns with known epidemiological factors, such as school opening times and vaccination coverage.

Main Results:

• Pertussis epidemics shifted from early/mid-year peaks before 1957 to the last quarter between 1958-1975.
• Since 1976, epidemics have exhibited a bimodal seasonal pattern with peaks in February and September.
• Increased transmission correlates with school openings in September; a notable low occurs in February-March, potentially linked to declining vaccine uptake.

Conclusions:

• The bimodal seasonality of recent pertussis epidemics is likely driven by a combination of seasonal transmission lows and highs, possibly exacerbated by reduced vaccine uptake.
• The observed seasonal trends may reflect the increasing proportion of pertussis cases among unvaccinated or under-vaccinated preschool children.
• Further investigation into the natural history of pertussis and its interaction with vaccination status is warranted.