Global Disease Burden of Group A Streptococcus

Excerpt

Despite being in existence for hundreds of years, Streptococcus pyogenes (group A streptococci) remains a significant cause of global morbidity and mortality, with a particular impact in resource-limited settings. The vast majority of cases of acute rheumatic fever (ARF), rheumatic heart disease (RHD), acute post-streptococcal glomerulonephritis (APSGN), and invasive S. pyogenes cases occur in low-resource settings (Carapetis, 2005) (Figure 1).

Accurate estimates of the global disease burden are important in planning for disease control, allocating resources, advocating for interventions, and prioritizing new strategies and research. This is particularly relevant in light of the potential to invest in the development of a vaccine to control S. pyogenes disease (Moreland, et al., 2014) (for more information, see the chapter on vaccine development in this book). However, overall disease burden estimates are difficult, mainly because of the scarcity of comprehensive disease registries, the reliance on passive surveillance systems, and the underreporting of both acute and chronic cases. This is true in all regions, and particularly in countries where S. pyogenes diseases occur most frequently (Marijon, Mirabel, Celermajer, & Jouven, 2012).

Clinical manifestations of S. pyogenes are among the most diverse of any human pathogen (Ralph & Carapetis, 2013). S. pyogenes has a varied presentation that ranges from seemingly benign pharyngitis and skin infections to more severe glomerulonephritis and sepsis, as well as devastating rheumatic heart disease (RHD), toxic shock syndrome, and necrotizing fasciitis.

In 2005, a review of the global burden of group A streptococcal diseases was published, using conservative methodologies that were deliberately designed to under-estimate the burden (Carapetis, 2005; Carapetis, Steer, Mulholland, & Weber, 2005b). At that time, it was estimated that a minimum of 18.1 million people were suffering from invasive S. pyogenes diseases, with an additional 1.78 million incident cases occurring each year. These estimates did not include over 111 million cases of streptococcal pyoderma and 616 million cases of S. pyogenes pharyngitis each year (Carapetis, Steer, Mulholland, & Weber, 2005b). A subsequent review published in 2008 provided updated data on the RHD burden from Asia, which estimated between 1.96 and 2.21 million cases of RHD in Asian children 5 to 14 years of age (Carapetis, 2008). These studies also highlighted the dramatic gaps in reliable recent disease burden data from many regions, particularly Asia, Eastern Europe, and Latin America.

In this chapter, we will build on the 2005 review by including the considerable amount of studies that have been performed since that review. Improved capacity for case detection that includes the use of echocardiography, as well as an increase in notification, have been associated with increases in reported rates of S. pyogenes–related diseases in low-resource settings.