The effect of group A streptococcal carrier on the epidemic model of acute rheumatic fever

Abstract

Background Group A streptococcus (GAS) is the most frequent cause of bacterial pharyngitis in school-aged children. The postinfection sequel as acute rheumatic fever (ARF) and rheumatic heart disease that cause morbidity and mortality among young people is public health concerns in several developing countries. Asymptomatic carriage state of GAS is not fully understood in terms of host and bacterial factors. Although the ability of transmitting GAS of the asymptomatic carriers is relatively low, they may present the reservoir of the epidemic. A fraction of GAS carriers is difficult to estimate in practice and may greatly vary between populations. Understanding the role of carriage on the transmission dynamic of GAS is important for assessing the public health impact of the ARF. Method This study investigates the effect of GAS carriers on both the transmission and dynamic of ARF cases by using a mathematical model. Result We derive the sufficient conditions for which the GAS can spread or extinct from the naive population under the variation of the fraction of symptomatic cases over the incidence of GAS. The threshold is possible to occur in general, but the last condition which is rather restrictive and involves parameter uncertainty. The increasing of carriers in the endemic state leads to the reduction in magnitude of the reproduction number and the number of ARF patients. We demonstrate that the adjustment of parameters can be carried out by the use of endemic state and some specific data. Conclusion We show theoretically that the presence of asymptomatic carriers may induce the epidemic threshold and reduce the virulence of GAS and the prevalence of ARF.

The rise and fall of acute rheumatic fever and rheumatic heart disease: a mini review

“…RHD can lead to complications such as heart failure, endocarditis, embolic stroke, and atrial fibrillation, which may be fatal in severe cases ( 9 ). RHD is the leading cause of morbidity and mortality in children aged 5–15 years ( 1 ).…”

“…Acute pharyngitis is an acute, specific or non-specific inflammatory response of the pharyngeal mucosa, submucosa and lymphatic tissues and is a common disease that occurs in children between the ages of 5 and 15 years ( 1 , 9 ). The main clinical manifestations are sore throat, painful swallowing and fever.…”

“…Acute rheumatic fever (ARF) and rheumatic heart disease (RHD) are immune disorders caused by group A Streptococcus (GAS) infections; these conditions were the leading cause of death among children in the 1920s ( 1 , 2 ). However, the improvement of economic and living conditions, as well as the widespread use of antibiotics, led to a marked decrease in the frequency of GAS infections, which was paralleled by a decrease in the incidence of ARF and RHD ( 3 – 6 ).…”

Acute Rheumatic Fever and Rheumatic Heart Disease: Highlighting the Role of Group A Streptococcus in the Global Burden of Cardiovascular Disease

“…However, there is recent evidence that other routes may play an important role in the transmission: oronasal secretions, small airborne particles, skin-to-skin contact, surfaces, bedding and fabrics, food, and insects [ 6 , 7 ]. Though spread is from infectious individuals, some studies suggest that transmission from carriers may be of epidemiological importance [ 8 , 9 , 10 ].…”

Modes of transmission and attack rates of group A Streptococcal infection: a protocol for a systematic review and meta-analysis

“…dust (airborne) [20][21][22][23][24], skin-to-skin contact (direct contact) [19,[25][26][27], surfaces (indirect contact) [28][29][30], bedding and fabrics (indirect contact) [31][32][33], food (vehicle) [34,35], and insects (biological vectors) [36][37][38]. Both the infectious and carrier state may lead to transmission, dominated by the infectious state [39,40]. A few studies have reported Strep A transmission from carriers to uninfected individuals who have subsequently become symptomatic [41][42][43][44].…”