A 2012 outbreak of adenovirus that occurred in a United States neonatal ICU was traced to medical instruments used for retinopathy of prematurity, or ROP, exams, according to a recent report in Infection Control Hospital Epidemiology.

Thirteen neonatal ICU (NICU) patients were affected by the outbreak, including one patient who died from adenoviral bronchopneumonia, according to Nicholas D. Hysmith, MD, of the department of pediatrics at the University of Tennessee Health Science Center College of Medicine, and colleagues.

The outbreak was first detected after two index patients with conjunctivitis tested positive for adenovirus. The initial cases led to facilitywide screening of all NICU patients. Qualitative and semiquantitative real-time PCR (qPCR) was used to test nasopharyngeal (NP) swabs obtained from the infants. Researchers conducted NP qPCR assessments three times a week to monitor new infections and viral clearance trends among cases.

“The availability of a rapid, reliable, in-house, real-time adenovirus PCR test made this outbreak monitoring approach feasible,” they wrote.

In addition to enhancing surveillance efforts, a multidisciplinary team was formed to guide infection control efforts, including extensive cleaning, contact precautions and enforcing family and visitor policies. Meanwhile, researchers investigated potential modes of transmission, including health care workers, family members, visitors and shared medical equipment.

All 13 patients who tested positive for adenovirus had an ROP examine in the previous month. Further investigation revealed that a recent ROP examination was associated with a greater risk for infection compared with no ROP examination (OR = 84.6; 95% CI, 4.5-1,601).

Hysmith and colleagues examined the sterilization procedure for ROP ophthalmological instruments. They reported that scleral depressors and blepharostats were sterilized after use and cleaned before each exam with alcohol antiseptic wipes and chlorhexidine gluconate solution. However, the researchers said adenoviruses have previously shown to have resistance to common disinfection strategies and can persist in the environment, making them “particularly suited for transmission via hands or contaminated instruments.”

After the outbreak was detected, health care providers used separate autoclaved instruments for each exam. No additional cases were reported, and outbreak response efforts were terminated 33 days after the first cases were identified. However, “best practice” measures and heat-sterilized instruments continue to be used during ROP examinations in the facility, according to the researchers.

Hysmith and colleagues said their findings indicate that ROP exams were the likely source of adenovirus transmission. They also recommended the use of real-time quantitative molecular diagnostic assessments for surveillance and viral load monitoring during future adenovirus outbreaks because it played an important role in controlling and ending the current outbreak.

“This adenovirus outbreak is a sobering reminder that our modern NICUs can still fall prey to a type of outbreak that was well described more than 20 years ago,” they concluded. “We hope that describing our experience will prompt pre-emptive evaluation of potential modes of adenovirus transmission, including ROP exam procedures, in other NICUs.” – by Stephanie Viguers

DisclosuresThe authors report no relevant financial disclosures.