Dead Case Investigation caused by Influenza A (H3) and Rapid Survey of Incidence of Influenza in Schools, Sankamphaeng District, Chiang Mai Province, Thailand, August – September 2012

Abstract

Background: Bureau of Epidemiology and Chiang Mai Surveillance and Rapid Response Team conducted investigation between September 1 - 6, 2011 to verify diagnosis and confirm dead case and the outbreak, to identify source of infection and epidemiological linkage, to describe epidemiological characteristic and magnitude of the outbreak, to survey the incidence of Influenza - Like Illness (ILI) and influenza in school setting, and to recommend the prevention and control measures.
Method: The team reviewed medical record of the death, interviewed family members, colleagues (School-B), and villagers, and collected throat swabs of family members for confirmation of influenza. A suspect case was defined as a person who lived in Sankamphaeng (SKP) district or studied or worked in school in the SKP district had at least two symptoms as follows: fever, cough, sore throat, and rhinorrhea with onset date between August 1, and September 1, 2011. A confirmed case was a suspect case with positive result of influenza A (H3) from respiratory secretion by RT-PCR. We reviewed the number of cases in the influenza-like illness (ILI) reporting system in 2010 and 2011 of SKP Hospital, nearby hospitals in other districts of Chiang Mai. Interview local SRRT in health center and district health office about suspected influenza outbreaks in school in SKP District and conducted school survey of the incidence of ARI among 9 of 11 schools in SKP District and collected either throat swab or nasal swab from students and teachers for influenza testing in the National Institution of Health (NIH) and Siriraj Hospital. Interviewed all students, teachers, and staffs about their clinical and treatment in School-A and School-C also environment survey in School-A and C.
Result: A fatal influenza A (H3) case of 57 years old female school chef with her two daughters was found. Her underlying disease is untreated diabetes. Visiting her husband who admitted caused by myocardial injury at a hospital was a suspect source of infection and received Oseltamivir lately. In 2011, Chiang Mai reported ILI cases in the surveillance was increased in mid-August that it raise earlier than the incidence of ILI in 2010 Influenza outbreaks in late August 2011 by survey, there were high attack rate of ILI in 3 schools in SKP subdistrict and Influenza A (H3) was identified by RT-PCR but we did not find linkage evidence with the death.
Conclusion: This was a family cluster of influenza A (H3) with a fatal case who had untreated suspect DM and late specific treatment for influenza. Several confirmed influenza A (H3) outbreaks in schools in SKP District, Chiang Mai were concurrently happening in late August to early September 2011. Oseltamivir supply for private clinics in SKP district was given and active surveillance for ARI with severe complication was conducted. Incidence of ARI among school children in SKP sub-district was higher than the incidence of ARI among students in other sub-district. Only influenza A (H3) was found in both primary and secondary schools without severe cases. No any linkage found between dead case and outbreak in schools.