Haemophilus influenzae Type a Sequence Type 23, Northern Spain

Area of Science:

• Medical Microbiology
• Epidemiology
• Infectious Diseases

Background:

• Haemophilus influenzae type a (Hib) is a significant pathogen, particularly in invasive infections.
• Sequence type 23 (ST23) represents a specific, potentially virulent strain of Hib.
• Invasive Hib infections can lead to severe health outcomes, especially in young children.

Purpose of the Study:

• To investigate the occurrence and epidemiology of Haemophilus influenzae type a infections.
• To determine if a cluster of ST23 Hib infections in a daycare setting represented a broader outbreak.
• To assess the incidence of Hib ST23 invasive infections in northern Spain from 2013-2020.

Main Methods:

• Active surveillance for Haemophilus influenzae infections was initiated following two consecutive cases.
• Epidemiologic data collection focused on invasive Hib infections in children.
• Laboratory analysis confirmed the identification and strain typing (ST23) of Haemophilus influenzae isolates.

Main Results:

• Two consecutive cases of invasive Haemophilus influenzae type a, sequence type 23, were identified in children attending the same daycare in 2019.
• Despite the initial cluster and the known invasiveness of the strain, no additional cases of Hib ST23 were detected during the surveillance period (2013-2020).
• The surveillance did not reveal a sustained or widespread outbreak of this specific Hib strain.

Conclusions:

• The initial two cases of invasive Hib ST23 in a daycare setting did not lead to further identified infections within the study period.
• Enhanced surveillance did not detect additional invasive Haemophilus influenzae type a, ST23, cases in northern Spain between 2013 and 2020.
• Further research may be needed to understand the epidemiology and potential for sporadic invasive Hib ST23 infections.