Clinical and virological analysis of epidemic keratoconjunctivitis caused by adenovirus type 54 in a regional ophthalmic clinic in Kyushu, Japan

BACKGROUND: Human adenovirus type 54 (HAdV-54) is a novel type of adenovirus that belongs to species D and has thus far been detected only in Japan in patients with epidemic keratoconjunctivitis (EKC). There was a large nationwide outbreak of HAdV-54 EKC from 2015 to 2016 in Japan. The clinical characteristics of an outbreak of HAdV-54 conjunctivitis treated in a regional ophthalmic clinic in Fukuoka, Japan, in 2016 were analyzed. PATIENTS AND METHODS: A consecutive series of 55 cases diagnosed clinically as EKC confirmed by HAdV-54 detection from conjunctival scrapings by polymerase chain reaction (PCR) method between 17 June 2016 and 29 August 2016 were enrolled. Viral DNA copies were counted by real-time PCR method. The clinical findings were recorded at the first visit to the clinic and evaluated. RESULTS: In the analysis of the relationship between mean clinical score groups and several factors, such as days after onset, sex, HAdV DNA number on a logarithmic scale, and age, most factors did not show a significant difference in clinical score between groups. However, mean clinical score of cases aged <23 years was significantly higher than that of cases aged ≥23 years (P<0.01). The correlation coefficient between DNA copies on a logarithmic scale and clinical score was 0.280, and a significant correlation was observed (P<0.05). Multiple subepithelial corneal infiltrates (MSI) were observed in 24 out of 31 cases (77%). CONCLUSION: These results suggested that the clinical features in the early phase of HAdV-54 keratoconjunctivitis were milder but the rate of MSI observed in the late phase was higher than those in previous epidemics of several HAdV types. The significant difference in clinical severity between age groups might be a virological characteristic of HAdV-54.