Scarlet Fever Outbreak Investigation in Mueang District, Nan Province, Thailand, 12th – 15th January 2012

Abstract

Background: In January 2012, an outbreak of suspected scarlet fever was detected in Mueang District, Nan Province. FETP joined Surveillance and Rapid Response Team (SRRT) of Nan Hospital and Office of Disease Prevention and Control 10 to investigate the outbreak during January 12th-15th, 2012. The objectives were to identify etiologic agent, confirm diagnosis and outbreak, assess magnitude, describe epidemiologic characteristics of outbreak and give recommendations for prevention and control of the outbreak.
Methods: We reviewed scarlet fever situation, patients’ medical records in Nan Province from R506 system and Nan Hospital database, and interviewed pediatrician, medical epidemiologist, parents, caretakers and teachers in every school and nursery in Mueang District. Active case finding was conducted in 2 institutions with the highest number of cases. A suspected case of scarlet fever was defined as a under-15-year-old child who visited Nan Hospital or attended Nursery A or School B in Mueang District, Nan Province during November 1st – January 13th and either developed following symptoms (fever, sore throat and diffuse rash) or diagnosed as scarlet fever by a physician. A confirmed case was defined as a suspected case who was tested positive for Streptococcus pyogenes by bacteria culture. Environmental surveys in Nursery A and School B were also performed.
Results: Number of reported scarlet fever cases in Nan Province had significantly increased from 2 cases in December 2011 to 32 cases in January 2012, with majority of cases (60%) occurred in Mueang District. Median age of the cases was 3 years (Range: 0-13 years) and male to female ratio was 1.3:1. Four cases were confirmed with Streptococcus pyogenes infection. In Nan Hospital, we found 3 confirmed cases and 11 suspected cases. Seven schools/nurseries reported suspected cases of scarlet fever. Of those, 5 and 10 cases, with attack rate of 3.2% and 1.3%, were identified during active case findings in Nursery A and School B respectively. Most of the cases attended nurseries and kindergarten (92.6%). All of them had only mild symptoms and fully recovered. Although 18.5% were hospitalized, no fatal cases occurred. Clinical manifestations of cases were fever and diffuse rash (100%). Crowded environment and no isolation room for sick children in Nursery A, and close contacts among children in both nursery and school were observed.
Discussion and conclusion: This outbreak was confirmed as scarlet fever by clinical and laboratory evidences. The high risk groups were children in nurseries and kindergarten schools, where symptomatic and contagious cases came into close contact with susceptible children. Direct contact with secretion and respiratory droplets of sick children in nursery/school probably played an important role of bacterial transmission in this outbreak. Early diagnosis, laboratory confirmation and proper antibiotic treatment were key factors in the success of epidemic control. Surveillance in nurseries and schools should be established for early detection of infectious diseases in children, especially enhancing a screening system and case isolation after detection of an outbreak.