Household transmission of invasive group A Streptococcus infections in England: a population-based study, 2009, 2011 to 2013

Abstract

Invasive group A streptococcal infection has a 15% case fatality rate and a risk of secondary transmission. This retrospective study used two national data sources from England; enhanced surveillance (2009) and a case management system (2011–2013) to identify clusters of severe group A streptococcal disease. Twenty-four household pairs were identified. The median onset interval between cases was 2 days (range 0–28) with simultaneous onset in eight pairs. The attack rate during the 30 days after first exposure to a primary case was 4,520 per 100,000 person-years at risk (95% confidence interval (CI): 2,900–6,730) a 1,940 (95% CI: 1,240–2,880) fold elevation over the background incidence. The theoretical number needed to treat to prevent one secondary case using antibiotic prophylaxis was 271 overall (95% CI: 194–454), 50 for mother-neonate pairs (95% CI: 27–393) and 82 for couples aged 75 years and over (95% CI: 46–417). While a dramatically increased risk of infection was noted in all household contacts, increased risk was greatest for mother-neonate pairs and couples aged 75 and over, suggesting targeted prophylaxis could be considered. Offering prophylaxis is challenging due to the short time interval between cases emphasising the importance of immediate notification and assessment of contacts.

Severe group A streptococcal infections in mothers and their newborns in London and the South East, 2010–2016: assessment of risk and audit of public health management

“…However, there were no other dual iGAS infections, suggesting that, in other potential cases, dual cases of iGAS may have been averted by prophylaxis. In a national study of household transmission, to prevent a case of iGAS, only 50 mothers and neonates have to be given prophylaxis, and mothers/babies accounted for one in five of dual cases . However, there is no study assessing the effectiveness of the guidelines in practice, although this is much needed.…”

“…The risk of secondary iGAS infection in close contacts of cases is elevated, particularly for mothers and their infants during the neonatal period, with an attack rate of over 25 per 100 person‐years at risk, although the risk of death is not elevated compared with other iGAS infections. As GAS is not usually carried in the vaginal flora, genital exposure peripartum arising from an exogenous source may be the cause of the high risk of iGAS infection.…”

“…Guidelines for the management of close community contacts of iGAS infection issued in 2004 state that antibiotic prophylaxis should be administered to both mother and neonate if either develops suspected or confirmed iGAS infection during the neonatal period (the first 28 days following birth) . A review of linked maternal/neonate cases found that to avert one case, 50 contacts need to receive prophylaxis …”

Managing scarlet fever

“…Statutory notifications, based on clinical symptoms consistent with this diagnosis, are submitted to local health protection teams 8. Cases of iGAS infection should also be notified urgently, so that close contacts can be identified early and advised to be vigilant for symptoms of GAS infection 22122…”

Genomic sequence investigation Streptococcus pyogenes clusters in England (2010–2015)

“…GAS outbreaks may implicate healthcare workers (HCW) and infection control practises. Predominantly, vulnerable patients including elderly individuals, postpartum mothers and neonates are at risk [2].…”