Possible nosocomial transmission of measles in unvaccinated children in a Singapore public hospital.

INTRODUCTION

Measles is an acute, highly communicable viral disease, with measles outbreaks usually occurring in settings where there are unvaccinated populations. After being notified of a cluster of five measles cases in a Singapore public hospital in August 2011, the Ministry of Health Singapore conducted an outbreak investigation.

METHODS

Active case detection was conducted, and all notified cases' movement history within the hospital were reviewed to determine any common exposures in place and time. Cases were classified as nosocomial if they had contact with other measles cases in the hospital seven to 21 days before onset dates. Laboratory testing included serological and molecular diagnostic methods.

RESULTS

Of the 14 cases, seven cases were nosocomial cases. Investigations identified two wards where cases were epidemiologically linked. Two cases in Ward A were of D8 genotype and genotypically 100% identical, thus confirming a common source of infection. The six cases in Ward B (including one transferred from Ward A) had overlapping periods of admission and three cases were of the same D8 genotype, with a single nucleotide difference.

DISCUSSION

The epidemiological linkages of the cases and laboratory findings suggest nosocomial transmission in Wards A and B. As a result of this investigation, the hospital implemented a new policy of isolating suspected measles cases instead of waiting until they had been laboratory confirmed. This investigation emphasizes the importance of early identification and isolation of suspected measles cases within health care institutions and reinforces the requirement for high measles vaccination coverage of health care workers.