Outbreaks of Varicella Zoster in a Military Nursing Institute: Infection Control in Hospital and Institutional Environments

Varicella zoster (VZ) is a highly contagious exanthematous disease. The Indian VZ clade 5 has a high outbreak potential with attack rates of 90%, which thwarts all the infection control endeavors in hospital and institutional environments. Four VZ outbreaks occurring over four different years were investigated with military nursing students in a tertiary-care hospital in order to delineate infection control protocols.
VZ outbreaks were investigated by hospital infection control committee utilizing standard definitions and protocols after establishing epidemiological linkage. A total of 114 nursing students were evaluated through a questionnaire developed to assess clinicodemographic, exposure, confinement and vaccination parameters. Outbreak control measures included isolation of patients; quarantined close-contacts and suspects; acyclovir treatment; immunization of susceptible candidates against VZ.
There were four different outbreaks comprising a total of 23 patients including five breakthrough patients with cumulative attack rate of 39%. Most patients had mild VZ. Most common sources were friends. Also, 25 students had no exposure to VZ or VZ vaccine, and were identified to be susceptible candidates and accordingly, were vaccinated.
Outbreaks of VZ are emerging in the developing countries due to inadequate immunization coverage, primary failure to seroconvert, or failure to mount immune response despite seroconversion, or secondary failure due to waning immunity. Outbreaks of VZ may have variable epidemiological dynamics and may not be controlled with standard infection-control programs. There is a need to augment existing capabilities for optimizing outbreak management in institutional settings.