Confirmed cases of invasive Haemophilus influenzae across the EU and EEA rose to 5,856 in 2024, continuing a post-pandemic increase driven by the return of typical respiratory transmission patterns and a notification rate reaching 1.3 per 100,000 population.
Surveillance figures released in an annual epidemiological report for 2024 document an upward trajectory for the pathogen following lower case counts recorded during the COVID-19 pandemic era. Total confirmed cases previously stood at 5,520 in 2023, 4,002 in 2022, 1,693 in 2021, and 1,838 in 2020. The notification rate of 1.3 cases per 100,000 population represents the highest observed level over a five-year window, climbing from 1.2 in 2023, 0.9 in 2022, and 0.4 in both 2020 and 2021.
Childhood Vaccination Programs Keep Serotype B Cases Low
Serotyping data was accessible for 55% of the total reported cases in the surveillance dataset. Among infections with a known serotype, non-capsulated strains accounted for the vast majority at 82%. Serotype b (Hib) represented 6% of known serotyped cases—amounting to 191 infections—which marks a slight increase from 5% in 2023. Serotype f appeared in 5.7% of cases, totaling 183 infections.
Epidemiologists attribute the comparatively low proportion of serotype b cases to the enduring effectiveness of childhood vaccination programs implemented across EU and EEA nations.
Medical Report Suggests Pathogen Spreads Within Domestic Environments
Beyond broad regional surveillance, clinical literature examines how the pathogen spreads within domestic environments. A documented medical report details an elderly cohabiting couple who developed pneumonia ten days apart. Sputum isolates recovered from both patients displayed identical minimum inhibitory concentration profiles across all tested antimicrobial agents, providing circumstantial evidence consistent with household transmission.
Kyotani, T. For one patient, findings listed a white blood cell count of 8,630/μL containing 81.2% neutrophils and 11.0% lymphocytes, a blood urea nitrogen level of 35.1 mg/dL, a creatinine level of 1.6 mg/dL, and a C-reactive protein measurement of 34.3 mg/dL.
The 90-year-old female patient also presented with chronic heart failure, atrial fibrillation, and dyslipidemia, and was receiving a regimen of bisoprolol at 1.5 mg per day, furosemide at 10 mg per day, dabigatran at 220 mg per day, minodronic acid at 50 mg per day, ramelteon at 8 mg per day, rosuvastatin at 2.5 mg per day, azosemide at 30 mg per day, and carbocisteine at 1,500 mg per day. Around the time her husband was admitted, she developed a productive cough and exertional dyspnea. She initially received oral amoxicillin/clavulanic acid for five days as an outpatient without improvement, subsequently developing worsening dyspnea, general fatigue, loss of appetite, and difficulty walking before being admitted 10 days after her husband.
Molecular epidemiological analyses were not performed, so isolates from the two cases could not be confirmed as the exact same strain.
While molecular confirmation in household settings can be limited, prior investigations—such as a study of 18 child-parent pairs that found identical pulsed-field gel electrophoresis patterns in 14 pairs, representing 77.8%—support the biological plausibility of household transmission.