Trace-back investigation on consecutive Paratyphoid outbreak in a junior high school during 2009-2014

Objective To explore etiology of three consecutive Paratyphoid outbreak in a junior high school in Xuan'en County during 2009-2014,to reduce future outbreak risk and protect health of teachers and students.Methods Detailed history information on activities,drinking,diet and close contacts of the patients were collected.The outbreaks were compared with previous paratyphoid outbreak in Xuan'en County in epidemiological characteristics,clinical treatment and outcome.Laboratory tests were investigated,and traced back for possible risk factors.Results About 2.65%,2.76% and 2.25% of all students affected in the Paratyphoid outbreak,respectively,with no severe and fatal cases.Only 3 out of 75 water samples from centralized water supply,well and bottled water were eligible.No salmonella,shigella,eg.coli O157 was detected.No infectious agents was detected in 68 environmental specimens around school and patient house and 70 food samples from school canteen during the past week.Blood test and rectal swabs were negative among 79 canteen staffs and 21 family members.Eighteen healthy teachers and 117 students were randomly selected for health monitoring,3 students were detected salmonella paratyphi A and abnormal serum hypertrophy reaction was found in 10 blood samples.Seven patients in 2014 outbreak were the same students in 2013 outbreak.Average time for antibiotic treatment in hospital was 8 days,less than the standard treatment time,and no stool Salmonella culture before discharged from the hospital.Classmate,share the same table with patients,living in the same dormitory,close friend had the highest risk of being infected.PFGE source attribution analyses from in 38 Paratyphi strains in 2009-2014 showed high homologous rate.Conclusion Consecutive outbreak occurred in this school related with incomplete treatment on patients,no timely identification and proper management on source of infection.Schools,medical institutions play an important role in limiting the spread of infectious diseases by strengthen infectious disease monitoring and management guidelines.