An investigation of influenza outbreak in aschool in Sanpatong District, Chiang Mai Province, August 2018

Abstract

          On 28 August 2018, six suspected influenza infection patients at a school in Sanpatong district were notified to Sanpatong SRRT Center. We investigated this event to confirm diagnosis, outbreak, describe the epidemiology of outbreak and to implement control measures. We conducted the descriptive study by reviewing medical records and did the active case findings. Retro-prospective cohort study was conducted by an interview with questionnaire to search for determinants or risk behaviors toward influenza infection. Environmental investigation was performed by surveying general condition of the school and interviewing teachers. Laboratory study was tested by collecting throat swabs to determine genetic material of influenza virus by PCR. Results showed that nine cases were confirmed influenza infection and ten cases were probable influenza infection. Ratio of female per male was 1.38:1, average age was 14.20 years old. The attack rate was 12.26%. Risk factor of this outbreak found that the students were seated nearby the influenza patients in the study room (RR =3.21, 95% CI = 1.44 - 7.17). The environmental factors showed distance between desks was too close, less than 1 meter, and the room had poor ventilation. Laboratory study could detect the type of H3N2 influenza virus.  It was to confirm the outbreak of influenza infection at a school in Sanpatong district, Chiang Mai province between 21 August – 2 September 2018 had 19 cases. Pathogen of this outbreak was influenza A virus subtype H3N2.