Rescue of Severely Immunocompromised HIV‐Positive Persons. Part 3
Varicella disease in adults is uncommon in the United States because most adults have naturally acquired immunity. National seroprevalence data from 1988 to 1994 showed that 95% of adults 20 years old were immune to varicella‐zoster virus (VZV). In addition, adults comprised only 2%–4% of varicella cases in outbreaks reported from a varicella surveillance site during 1995–2005.
In December 2008, the Connecticut Department of Public Health was notified of a varicella outbreak in a residential facility for adults with intellectual disabilities (facility A) operated by the Connecticut Department of Developmental Services. The Connecticut Department of Public Health subsequently undertook an investigation to describe the outbreak and identify challenges in case management and outbreak control in this setting.
Case investigation. Facility A employed 145 staff and housed 70 residents with various levels of intellectual and physical disabilities in apartments in 3 buildings. Each apartment had 3 bedrooms with 2 beds in each bedroom. Staff included nursing, direct care, physical and occupational therapists, psychologists, cleaning staff, and clerical staff. A varicella case was defined as a generalized maculopapular rash (with or without vesicles and without another apparent cause) occurring between 1 November 2008 and 1 February 2009 in a resident or employee in facility A. Cases were identified by facility medical staff and/or chart review.
Information on all residents was abstracted from medical charts and facility admission histories using a standardized form and from interviews with facility caregivers. Staff case patients were interviewed by using a standardized case investigation form.
Laboratory testing. Serum samples were tested for VZV‐specific immunoglobulin M (IgM) and immunoglobulin G (IgG) by using an in‐house Centers for Disease Control and Prevention assay as described elsewhere and an enzyme immunoassay at a commercial laboratory. VZV DNA isolation from skin lesions by polymerase chain reaction (PCR) and genotyping were performed as described elsewhere. To identify VZV in the environment, sterile polyester swabs moistened with phosphate buffered saline were used to collect samples from various surfaces ( cm2 sample area) in residents’ rooms and common areas. Samples were collected from residential building 2, where no cases were identified, as control samples. Environmental samples were collected during the outbreak investigation and 2 months after rash onset in the last case. VZV detection and genotyping of the environmental samples by PCR was done as reported elsewhere. Laboratory staff was blinded as to whether specimens were case or control samples.
Definitions and statistical analysis. The attack rate was calculated as the proportion of cases among the residents of facility A. Residents’ degrees of intellectual and physical disabilities were categorized by an intelligence quotient score (moderate, 35–55; severe, 20–40; or profound, <20) and by functional ability (requiring full physical assistance, some physical assistance, or verbal and/or visual and/or psychosocial prompts). We used a Student t test for continuous variables and Pearson χ2 or Fisher exact test for categorical variables to analyze data. A significant association was defined as one with a 2‐sided P value of <.05. Approval from an institutional review board was not required because this investigation was conducted as part of a public health response.