An outbreak of norovirus in a District of Columbia elementary school last year was probably transmitted by unclean computer mouses and keyboards.
The Centers for Disease Control and Prevention was notified after 27 students and two staff members experienced symptoms of gastroenteritis (defined as nausea, vomiting, or diarrhea) within a 4-day period.
After inspecting the classrooms, CDC staff administered questionnaires to all staff and students. Results showed that students assigned to one particular first-grade classroom had almost double the risk of gastroenteritis during the 4-day period (relative risk 1.94). The affected classroom was the one that housed the school's computers, which were shared by students and staff. Foodborne illness was ruled out because no food was served at the school (MMWR 2008;56:1340–3).
Environmental samples taken from a computer mouse and keyboard contained norovirus subtype GII. This strain also was found in stool samples from two persons who had been on the site.
At the CDC's urging, the school cleaned all shared computer surfaces with a bleach solution, and all students and staff were restricted from the school until 72 hours after resolution of their illness to avoid recontamination.
In a commentary, the CDC noted that prior research has shown that norovirus can be transmitted to fomites and that a surrogate marker for norovirus, feline calcivirus, has been shown to survive on computer mouses and keyboards for up to 2 days.