Notes from the Field: Varicella Outbreak Associated with Riding on a School Bus - Muskegon County, Michigan, 2015.

On December 3, 2015, Public Health-Muskegon County (PHMC) in Michigan was notified by a local kindergarten-grade 2 school that a student aged 8 years (the index patient) had been sent home because of a rash suspected to be varicella (chickenpox); the rash had not been observed the previous day. Investigation by PHMC revealed that the student was one of five siblings in household A, none of whom had a history of having received any immunizations. During the preceding month the index patient's two older siblings (aged 12 years and 25 years) and two younger siblings (twins, aged 4 years) had been excluded from other schools in this rural district because of rashes that also were suspected to be varicella. Investigators also learned that a parent in household A had received a physician diagnosis of herpes zoster (shingles) nearly 7 weeks earlier, on October 20, after having been evaluated for a painful, unilateral trunk rash that had begun 3 days earlier, and for which acyclovir was prescribed. PHMC could not confirm whether any advice regarding prevention of possible transmission of varicella zoster virus to susceptible contacts was provided. The other children in household A had rash onsets on November 3, November 18 (two children), and November 22. The index patient rode a school bus and was the first student on and the last off each day; none of the index patient's four siblings attended the same school or rode on the same school bus as the index patient. Public health investigators subsequently linked three more cases in children to sharing the same school bus as the index patient.