Investigation of an outbreak of acute hemorrhagic conjunctivitis in a school in Bao'an district, Shenzhen, 2023

Objective To investigate an outbreak of acute hemorrhagic conjunctivitis in a school in Bao'an district, Shenzhen of Guangdong province, in 2023, identify associated risk factors, and suggest prevention and control strategies.

Methods A field epidemiological investigation was carried out, descriptive epidemiological analysis was done on the clinical symptoms and distribution of three types of cases who met the case definitions and a retrospective cohort study was conducted for risk factor analysis. Conjunctival swabs and environmental smears were collected the detections of enterovirus 70 (EV70) and coxsackievirus A24 (CV-A24) with real-time fluorescence quantitative reverse transcription-polymerase chain reaction (RT-PCR).

Results In 1 487 students, 123 cases of acute hemorrhagic conjunctivitis were identified with an attack rate of 8.27%. The main symptoms included conjunctival hyperemia (90.25%), secretory ocular discharge (74.80%), foreign body sensation in eye (51.22%), and ocular pruritus (47.76%). The differences in attack rate were significant among students on different floors and in different classes/grades (P<0.001). The outbreak lasted from 5 to 21 in September, and the case count peaked on September 15 (27 cases), and the incidence curve suggested person to person transmission. RT-PCR detected CV-A24 in 17 conjunctival swabs and 1 tap water handle smear. Multivariate log-binomial regression analysis identified significant risk factors, including having sibling with acute hemorrhagic conjunctivitis at the same school relative risk (RR)=18.589, 95% confidence interval (CI): 3.688−93.798, direct hand contact (RR=2.789, 95%CI: 1.248−6.231), and interaction with symptomatic classmate (RR=2.303, 95%CI: 1.008−5.259), and the other risk factors were not statistically significantly associated with the onset of the illness (P>0.05).

Conclusion  This was an outbreak of acute hemorrhagic conjunctivitis caused by coxsackievirus-A24 variant, the disease was mainly transmitted through close contacts with the cases, including direct hand contacts, while the transmission among family members was a key risk factor in some classes and grades. It is suggested to avoid hand contact with classmate with acute hemorrhagic conjunctivitis and strengthen the isolation of acute hemorrhagic conjunctivitis cases and individual protection in siblings.