Adenovirus Transmission in a Nursing Home: Analysis of an Epidemic Outbreak of Keratoconjunctivitis

<i>Background:</i> An epidemic outbreak of keratoconjunctivitis occurred in a nursing home in Madrid from August to December 2005. <i>Objective:</i> This article reports the outbreak, the infection control measures taken, and risk factors for keratoconjunctivitis. <i>Methods:</i> A cohort study was conducted on the nursing home staff and residents. Specific attack rates and relative risks with their 95% confidence intervals were estimated. A multivariate analysis (logistic regression) was performed proving odds ratios (OR) of becoming ill. Conjunctival swab samples were taken and tested for viral infection. More stringent infection control measures were implemented following the occurrence of the initial cases. <i>Results:</i> Forty-six cases were identified in the nursing home (infection rates of 30.5% in residents and 8.3% in workers). Total duration of the outbreak was 120 days. Corneal ulcer occurred in 3 cases. The factors appearing as independent risk factors were age (OR = 5.7 in people aged ≧90 years compared to those aged <80 years), cognitive impairment (OR = 2.64) and nursing home floor (OR = 2.74 for the first floor, where the outbreak started). Adenoviral DNA was amplified in 10 samples, and 8 of them could be typed as adenovirus serotype 8. <i>Conclusions:</i> Early adoption of adequate hygiene measures is essential to control these outbreaks. In nursing homes with a high number of people with cognitive impairment, an additional effort should be made when the first cases occur to provide such people an increased and improved care and monitoring.