Varicella and Zoster, 2015

During 2015, 361 varicella cases (7 per 100,000 population) were reported. One hundred sixty-seven cases (46%) were reported from the metropolitan area. Cases ranged from 6 weeks to 97 years of age. Fifty (14%) cases were <1 year of age, 107 (30%) were 1-5 years of age, 126 (35%) were 6-12 years of age, 27 (7%) were 13-17 years of age, and 51 (14%) were ≥18 years of age.

Outbreaks in Minnesota K-12 schools have been declining markedly in number and size since vaccination requirements were phased in, beginning in 2004. In 2015, only one school reported an outbreak with 6 cases in a grades K-4 school; 5 were unvaccinated due to parental refusal. Four additional cases were unvaccinated siblings of the cases. Overall, 90% of students at the outbreak school were fully vaccinated. By comparison, 10 elementary schools with similar enrollments had cases that did not result in outbreaks; the average immunization rate at those schools was 96%. Two outbreaks were reported in childcare centers, one with 10 cases and one with 6 cases. All cases were too young to be vaccinated.

Seven cases were hospitalized, but there were no deaths. One was <1 year of age, 2 were 1-12 years of age, and 4 were ≥13 years of age. Five had severe disease and/or complications including pneumonia, bacterial cellulitis and group A streptococcal septicemia. Three had predisposing conditions for severe disease. Four had never received varicella-containing vaccine; 2 were underage for the vaccine, and 2 were adults who were never offered the vaccine. One case had been vaccinated with 1 dose of varicella vaccine and was hospitalized for observation rather than for severe disease, and vaccination history was unknown for 2 cases.

Varicella is sometimes identified by parents/guardians reporting to schools and child care facilities, rather than diagnosed by a provider. Of the 348 cases for which diagnosis information was available, 229 (66%) had visited a health care provider, 32 (9%) had consulted a provider or clinic by telephone, 5 (1%) had been identified by school health personnel, and 82 (24%) had not consulted a healthcare provider. Of the 332 cases for which information regarding laboratory testing was available, 86 (26%) had testing performed.

All zoster cases in children <18 years of age are reportable. Cases may be reported by school health personnel, childcare facilities, or healthcare providers. During 2015, 79 zoster cases were reported. Ages ranged from 1 to 17 years (median, 9 years). Laboratory testing by PCR or DFA confirms the diagnosis of zoster. Of the 73 cases for which information about testing was available, 39 (53%) had testing done; 37 (95%) of these were positive for VZV by PCR.

Zoster with dissemination or complications (other than postherpetic neuralgia) in persons of any age is also reportable. During 2015, 69 zoster cases with dissemination or complications were reported; 62 were hospitalized. Twenty-eight (41%) cases were ≥60 years of age, 30 (43%) were 30 to 59 years of age, and 11 (16%) were <30 years of age. Twenty-seven (39%) had underlying conditions or were being treated with immunosuppressive drugs. Twenty-three cases had meningitis, 20 had disseminated rash or disease, 17 had cellulitis or other bacterial superinfection, 8 had Ramsay-Hunt Syndrome, 6 had encephalitis or meningoencephalitis, 4 had Bell-like palsy, and 1 had myelitis. Immunocompromising conditions and immunosuppressive drug treatment were more common among cases with disseminated rash or disease (70%) than among those with meningitis without dissemination (17%). No deaths attributable to zoster were reported.

• For up to date information see>> Varicella (Chickenpox)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2015