Surveillance, Investigation, and Control of Scarlet fever – March 8, 2025

Abstract

Scarlet fever is caused by Group A Streptococcus bacteria and is transmitted through respiratory droplets and direct contact. Outbreaks commonly occur in schools and childcare centers. Although the illness is generally mild, if left untreated, it can lead to severe complications such as rheumatic fever and acute glomerulonephritis. Between 2022 and 2024, outbreaks have been reported in Europe and Japan. In Thailand, most cases are found in children aged 5–15 years. From January to February 2025, outbreaks were reported in multiple schools across various regions. This article reviews the basic knowledge of scarlet fever and outlines the guidelines for surveillance, investigation, and disease control. Scarlet fever is a notifiable disease under Thailand’s Communicable Disease Act B.E. 2558 (2015), with clear protocols for case reporting and laboratory confirmation. The objectives of outbreak investigation are to confirm the outbreak, study the epidemiological characteristics, identify risk factors, and implement control measures to prevent further transmission. The data used in investigations include patient information, contact and treatment history, and laboratory results. Descriptive analysis is performed based on person, time, and place. Diagnosis can be confirmed through culture, PCR testing, or serological testing. Control measures recommend that symptomatic patients complete a full 10-day course of antibiotics. However, prophylactic antibiotics are not recommended, except for individuals in close contact with those at high risk for severe illness, such as healthcare workers or caregivers of the elderly. Control efforts emphasize ensuring patients complete their prescribed antibiotic course. If not, they should refrain from close-contact activities for 21 days from symptom onset or until full recovery. Completing treatment and monitoring for complications are key to reducing the risk of severe outcomes.