An Cluster Event of Adenovirus Infection in Children Caused by a Contaminated Swimming Pool

Objectives To investigate the source of infection and the transmission route of an Cluster event among children with fever, sore throat and cough as main symptoms in Changtai county, Fujian province, so as to take effective control and preventative measures, and summarize experience and lessons.

Methods Epidemiological investigation was carried out and related specimens were collected for laboratory testing. A retrospective cohort study was conducted to examine the risk factors and to investigate the hygienic status of the swimming pool.

Results There was an outbreak of pharyngeal conjunctival fever in 22 members of a swimming school in Changtai county in Fujian province in September 2011, with an attack rate of 51.16%. The main symptoms of these cases were fever (100%) and sore throat (77.27%), etc. The first case occurred on 5^th September, the peak incidence was in 11^th September to 14^th September, but no new case was found after 15^th September, the epidemic lasted for 11 days. Of the 22 cases, 21 cases were team members (attack rate 52.50%) of the school, and 1 case was a coach (attack rate 33.33%), and there was no statistical difference in the attack rate (RR=1.6, 95%CI=0.3~8.0). The medium age of cases was 10 year-old (range:8~38 years old). There were 6 males (30.00% attack) and 16 females (69.57% attack rate), and the attack rate of female was higher than that of male (RR=2.3, 95%CI=1.1~4.8). A retrospective cohort study showed that the risk factor was an exposure to incomplete disinfected swiming pool water at B swimming pool in 4th September. In 13 throat swabs detected in the laboratory, 11 of which were positive for adenovirus nucleic acids. Hygienic survey showed that the change of water in swimming pools was on every Monday and the addition of disinfectant was only once in each time of changing water. The volume of this pool water was about 650 m³, the amount of bleaching powder should be 9.75 kg, but in fact, it was only 1.00 kg.

Conclusions Insufficient disinfection of water in swimming pool would easily lead to an eruption of pharyngo-conjunctival fever. Therefore, the administrative departments of public health should strengthen the management and supervision of swimming pools. A swimming pool that could not meet the requirement should be firmly closed until it could catch up relevant national standards to effectively prevent the occurrence of similar incidents.