Survey on Pharyngoconjunetival Fever Outbreak Caused by Type 7 Adenovirus

Objective To identify the pathogeny and risk factors for the children suffered from clustering high fever, sore throat and swollen tonsil, who had participated in a swimming training class during summer vacation in Shi Jiazhuang natatorium on July, 2011.

Methods Setting up a standardized definition to select cases and an uniformed epidemiological questionnaire to investigate and describe the epidemic characteristics. Pharyngeal swab samples were tested by PCR for etiological study. The risk factors, including swimming behavior, the history of swimming in pools No. 2~5 at this natatorium, and the relation of swimming at different time phase with the incidence, were analyzed by a retrospective cohort study. The children in this swimming training class were defined as the exposure group, and the children from dancing, English learning, drawing classes, swimming in other indoor pools, and swimmers who were trained at pool NO.1 of this natatorium were defined as non-exposure groups.

Results There were 131 cases suffered from pharyngoconjunctival fever in 225 middle and primary school children who participated in the swimming training class. The attack rate was 58.22%. The peak of the incidence was on July 18. The incidence rate in the exposure group with a history of swimming at pools No. 2~5 of this natatorium was 26.58 times higher than those in other training classes (RR=26.58, AR=56.03%, AR%=96.24%), 12.55 times higher than those swimming at other indoor pools (RR=12.55, AR=53.58%, AR%=92.03%), and 21.81 times higher than swimmers who were trained at pool NO.1(RR=21.81, AR=55.55%, AR%=95.41%). There was a time-response relationship between the incidence and swimming time phase (χ_trend²=29.43, P=0.000). The infection of type 7 adenovirus tested by PCR was revealed in 30 cases.

Conclusions The outbreak of pharyngoconjunctival fever in this swimming training class was caused by the pollution of type 7 adenovirus. Strengthening reporting infectious diseases, strictly disinfecting swimming pools, and reasonably arranging the number of trainees in each class to prevent the outbreak of infectious diseases.