Investigation on an outbreak caused by adenovirus type H7

Abstract

Objective To analyze the epidemiological characteristics, clinical features and etiological characteristics of a respiratory infection outbreak in a kindergarten in Jiangxi Province, so as to explore the causes of the outbreak and to provides experience for the prevention and control of such epidemic. Methods Cases were searched by interviewing the kindergarten principal and class teachers, and by referring to case information from medical institutions. Epidemiological questionnaires were used to collect the basic information of cases, clinical symptoms, disease onset and epidemiological history. The fluorescence quantitative PCR instrument was used to detect viral nucleic acid in the collected samples. The positive samples were proceeded for virus isolation. The amplified products were sequenced by a gene analyzer. At the same time, the full genome sequence of the virus was obtained by high-throughput sequencing. Results There were 32 cases in this outbreak and all were students. The incidence was 15.69% (32/204) and 90.60% (29/32) of the cases occurred in the April 27 to May 4. The mainly symptoms were high fever and dry cough accompanied by inflammatory changes in the lungs. The oldest case of 6 years old, the youngest one was 2 years old. The age of onset concentrated in range of 3-5 years old, accounting for 90.6% (29/32) of the cases. The incidence in the senior class 1 was 17.7% (6/34) was the highest. The incidence of preschool class was the lowest, only 9.4% (3/32). The difference was not statistically significant (x2=2.79, P=0.74). The incidence was 17.82% (18/101) in males , and 13.59% (14/103) in females. The difference was not statistically significant (x2=0.69, P=0.45). The incidence of students on the first floor was 13.08% (14/107) , and 18.56% (18/97) on the second floor. The difference was not statistically significant (x2=1.15, P=0.34). In addition, H7 adenovirus was detected in the samples by viral nucleic acid detection and whole genome sequencing. Conclusions The outbreak is caused by the human H7 adenovirus clustered outbreaks, mainly through close contact and respiratory droplets spread. Kindergarten poor ventilation, morning check and other systems are not perfect, is the main reason for the spread of the disease. Key words: Human adenoviruses; Respiratory tract infections; Pandemics; Epidemiologic studies