VANCOUVER, B.C. – An adenovirus outbreak in a Chicago neonatal intensive care unit led to an important realization about infection control.
"Soaking ophthalmology equipment in 70% isopropyl alcohol – which is commonly done in NICUs for retinopathy of prematurity equipment – is probably not sufficient to eradicate adenovirus contamination," said Dr. Emily Mawdsley, an instructor of medicine at the University of Chicago.
Seven infants in the NICU developed adenovirus keratoconjunctivitis in March 2009; four more with the condition, soon identified, had recently been discharged.
"Our initial call was to the pediatric ophthalmologist. He told us that he was at home sick with conjunctivitis," said Dr. Mawdsley, who works in the university medical center’s infectious diseases and global health section.
"After a discussion with him, he recalled that a pediatric ophthalmology resident had [recently] worked with symptomatic conjunctivitis. He’d been sent home, but not until after he had seen a few patients in the NICU," she said.
All the infants had recently been examined for retinopathy of prematurity. Virus typing by the Centers for Disease Control and Prevention revealed that the infants had the same virus strain as did the resident.
"So we took a look at the ophthalmology equipment," said Dr. Mawdsley, to see if that was the transmission vector.
Scleral specula and ocular depressors, which were reused on the unit after being soaked for 10-30 minutes in 70% isopropyl alcohol, were positive for adenovirus on polymerase chain reaction assay. They had been set aside in a sterile bowl several days earlier, after the unit suspended eye exams pending investigation results.
The ophthalmology cart handles, miscellaneous supply bags, a lens case, a headlight and battery pack, the contents of an eye spray irrigation bottle, and the alcohol bottle used for disinfection were also positive for adenovirus. Three samples grew live virus.
Previous studies have found 70% isopropyl alcohol – and 3% hydrogen peroxide – insufficient to kill adenovirus. The authors of one study recommended disinfecting ophthalmologic equipment with 70% ethyl alcohol or 5,000 ppm chlorine. They also recommended cleaning environmental surfaces with 1,900 ppm chlorine, 65% ethanol/0.63% quaternary ammonium, or 79% ethanol/0.1% quaternary ammonium (Antimicrob. Agents Chemother. 2006;50:1419-24).
To keep the virus in check, NICU staff started to clean equipment and surfaces with bleach or quaternary ammonium wipes and nurses wore gloves and gowns during their shifts. Sick children were segregated from well children and contact precautions were used, among other measures. Two NICU workers, two family members, and an additional infant developed conjunctivitis.
The outbreak was contained within a few weeks. Previously ill infants returned negative viral cultures, and the unit reopened to transfers. Retinopathy of prematurity exams were also resumed, but this time with disposable depressors and specula.
The virus didn’t cause infants respiratory compromise, Dr. Mawdsley said.
During the investigation, families were told that an exam had given their children conjunctivitis.
But "we didn’t have a lot of backlash from this. They could see that we were doing a lot to try to control spread. That contributed a lot to helping families feel better about what happened," she said.
According to Dr. Janet Englund, a pediatric infectious diseases professor at the University of Washington, Seattle, “There’s a great take-home message here.”
Dr. Mawdsley said she has no disclosures. Dr. Englund also reported no disclosures.