流行性角結膜炎の院内感染のウイルス学的，理論疫学的検討

Virological and theoretical epidemiological features of hospital infections of epidemic keratoconjunctivitis

　2つの異なる病院の眼科病棟（院内感染1：41床，院内感染2：30床）で発生した流行性角結膜炎の院内感染について検討した。罹患者はそれぞれ15例，28例で，発症率は19.0％，20.3％であった。アデノウイルス37型の全分離例のDNA切断パターンはすべて同一であった。院内感染1は病棟閉鎖によって終息し，院内感染2は感受性者数が不変であるにもかかわらず，11週間で制圧された。理論疫学のReed-Frostモデルを適用して求めた接触率は流行極期で0.18〜0.28／週，通常期で0.03〜0.05／週と推測された。流行性角結膜炎の伝播形式は水系伝染病に類似し，感受性者数を減らすか，接触率を下げる努力によって流行が制圧できることが理論疫学的に推測された。

Theoretical epidemiology analysis is a method used to extract mathematical models of the epi-demic curve. It is suited for investigation of epi-demic keratoconjunctivitis (EKC). We analyzed recent hospital infections of EKC in two institu-tions by applying the virological method and the Reed-Frost model. These two infections involved 15 and 28 patients each, representing 19.0% and 20. 3% of total inpatients at the time. We could isolate adenovirus type 37 (Ad 37) in all 14 specimens. All the 14 isolates showed identical cleavage patterns with those of Ad 37 prototype strain. Infection 1 was controlled by ward closing. Infection 2 was eradicated in 11 weeks, although the number of susceptibles remained unchanged. The probability of contact between two people in the group was estimated to be 0.18-0.28/week during the peak period and 0.03-0.05/week during the ordinary period according to the Reed-Frost model.

The above theoretical epidemiological analysis suggests that EKC spreads like a water-borne infec-tion and that it can be controlled by reducing the number of susceptibles or lowering the probability of contact.