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Invasive group A streptococcal infection: management of high-risk household contacts — MSRA MCQ

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HardInfectious DiseasesInvasive group A streptococcal infection: management of high-risk household contactsMSRA

A 76-year-old man requests advice after his wife was diagnosed with invasive group A streptococcal infection (iGAS) 6 days ago. She was admitted with necrotising fasciitis; Streptococcus pyogenes was isolated from blood and deep operative tissue. They live together and he provided personal care for her throughout the week before her diagnosis. She commenced intravenous antibiotics on admission. He is well, with no fever, sore throat, skin lesions, myalgia or focal pain. He has no penicillin allergy. No other household member has had confirmed or probable iGAS in the previous 30 days. What is the most appropriate management today?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: C — Prescribe phenoxymethylpenicillin for 10 days without screening and provide 30-day safety-net advice

Explanation lettering: E = shown as A · D = shown as C · C = shown as D · A = shown as E

This man is a household-type close contact: he had prolonged close contact with the index case during the 7 days before the wife’s iGAS diagnosis. He is also a high-risk contact because he is aged 75 years or over. High-risk household contacts should be offered chemoprophylaxis promptly, without screening, provided this is within 10 days of the index case’s diagnosis. First-line prophylaxis in an adult without penicillin allergy is phenoxymethylpenicillin for 10 days. All close contacts should receive information about symptoms requiring urgent assessment over the subsequent 30 days, including high fever, severe myalgia or localised muscle tenderness. A is incorrect because throat screening should not delay or determine prophylaxis in a high-risk contact. B would be appropriate for an asymptomatic contact who is not in a high-risk group. C incorrectly extends prophylaxis to the whole household: that is indicated if there has been another confirmed or probable iGAS case in the household within 30 days, which is specifically excluded here. E is inappropriate because he has no clinical features suggesting invasive or non-invasive GAS infection; emergency assessment is reserved for symptomatic contacts in whom invasive disease is suspected.

Reference: UK guidelines for the management of contacts of invasive group A streptococcus (iGAS) infection in community settings (2022; guidance page updated September 2025) — https://assets.publishing.service.gov.uk/media/64071ec5d3bf7f25fa417a91/Management-of-contacts-of-invasive-group-a-streptococcus.pdf UK guidelines for the management of contacts of invasive group A streptococcus (iGAS) infection in community settings (2022; guidance page updated September 2025) — https://assets.publishing.service.gov.uk/media/64071ec5d3bf7f25fa417a91/Management-of-contacts-of-invasive-group-a-streptococcus.pdf Accessible text versions of the 4 algorithms: management of contacts of iGAS in community settings (Updated 5 September 2025) — https://www.gov.uk/government/publications/invasive-group-a-streptococcal-disease-managing-community-contacts/accessible-text-versions-of-the-4-algorithms