Background: Few cross-population studies examining the epidemiology of invasive group B streptococcal (GBS) disease have been undertaken. To identify longitudinal trends in the burden and characteristics of infections, national surveillance data on diagnoses in England and Wales from 1991 to 2010 were analyzed.
Methods: A parallel review of laboratory-confirmed invasive GBS infection surveillance reports and isolates submitted to the national reference laboratory was undertaken. Cases were defined as GBS isolated from a normally sterile site.
Results: A total of 21 386 reports of invasive GBS infection were made between 1991 and 2010. The annual rate of reports doubled over the 20 years from 1.48 to 2.99 per 100 000 population. Significant increases were seen in all age groups but most pronounced in adults. Rates of early-onset (0-6 days) infant disease fluctuated but showed a general rise between 2000 and 2010 from 0.28 to 0.41 per 1000 live births. Rates of late-onset (7-90 days) disease increased steadily between 1991 and 2010 from 0.11 to 0.29 per 1000 live births. Resistance to erythromycin increased markedly from 2.5% in 1991 to 15% in 2010. The distribution of serotypes varied according to patient age and over time with type III increasing among early-onset cases and decreasing in adults.
Conclusions: Although risk of invasive GBS infection remains highest within the first few days of life, the relative burden of disease is shifting toward adults. The rise in incidence and antibiotic resistance makes development of an effective and safe vaccine all the more pressing.
Keywords: Streptococcus agalactiae; United Kingdom; drug resistance; epidemiology; streptococcal infections.