Haemophilus influenzae Type b Invasive Disease in Amish Children, Missouri, USA, 2014

Area of Science:

• Microbiology
• Epidemiology
• Public Health

Background:

• Invasive Haemophilus influenzae type b (Hib) infections, though largely preventable by vaccination, can still occur.
• Certain populations, including unvaccinated communities, may remain at risk for Hib outbreaks.
• Rare strains of Hib can pose unique epidemiological challenges.

Purpose of the Study:

• To report and characterize invasive Haemophilus influenzae type b infections in a cluster of Amish children.
• To investigate the genetic relatedness of the infecting strains.
• To explore potential transmission dynamics within the Amish community.

Main Methods:

• Case identification and clinical data collection.
• Molecular subtyping and whole-genome sequencing of Haemophilus influenzae type b isolates.
• Epidemiological investigation including travel history and contact tracing.

Main Results:

• Three cases of invasive Hib infection were diagnosed in Amish children over a 5-month period in 2014.
• Two of the cases involved children from neighboring rural households and were infected with a rare, genetically similar strain (sequence type 45).
• One infected child had a recent travel history, indicating possible introduction or maintenance of the strain.

Conclusions:

• The findings suggest a potential for the maintenance of a rare Haemophilus influenzae type b strain within unvaccinated Amish communities.
• Community transmission among unvaccinated individuals is a plausible explanation for the observed cluster.
• This highlights the importance of vaccination programs even in communities with historically low uptake.