Varicella and Zoster, 2018

In 2018, 325 varicella cases (5.8 per 100,000 population) were reported. One hundred ninety-seven (61%) were from the metropolitan area. Cases ranged from 19 days to 73 years of age. Forty-one cases (13%) were <1 year, 108 (33%) were 1-6 years, 86 (26%) were 7-12 years, 23 (7%) were 13-17 years, and 67 (21%) were ≥18 years of age. Eight cases were hospitalized; 3 were <1 year, 3 were 4-15 years, and 2 were >18 years of age. Seven of the hospitalized cases had never been vaccinated; 3 were underage for vaccination, 1 was unvaccinated due to parental refusal, 1 had a medical contraindication to vaccination, and 2 were adults who had never been offered the vaccine. In addition, there was 1 case that was reported while already hospitalized, and was likely a nosocomial infection. There were no varicella-related deaths.

Varicella cases are often identified by parents/guardians reporting to schools and childcare facilities, rather than directly reported by a clinician. Of the 325 cases for which information regarding diagnosis was available, 222 (68%) had visited a health care provider, 27 (8%) had consulted a provider or clinic by telephone, 1 had been identified by a school health professional, and 75 (23%) had not consulted a health care provider. Of the 317 cases for which information regarding laboratory testing was available, 117 (37%) had testing performed. Ten percent of cases occurred as part of an outbreak, defined as ≥5 cases in the same setting. Three outbreaks occurred in schools. Two were public schools, and one was a private school. The largest outbreak had 13 cases; 1 case was partially vaccinated, and 12 were unvaccinated. Of the unvaccinated cases, 9 were due to parental refusal, 1 was unvaccinated due to a previous report of disease, and 2 cases were unvaccinated because their parents reported they forgot to vaccinate.

Zoster cases in children <18 years of age are reportable in Minnesota; 61 cases were reported in 2018. Cases may be reported by school health personnel, child care staff, or healthcare providers. Ages ranged from 1 to 17 years (median 10 years). Varicella vaccine became a requirement for entry into kindergarten and 7th grade in 2004, and the incidence of zoster in children has declined from 15.7 per 100,000 population in 2006 to 4.7 per 100,000 population in 2018. In 2018, the PHL performed strain typing on specimens from 13 cases. Twelve of these cases had been vaccinated and of these, 11 (92%) were positive for the vaccine strain and 1 (8%) was positive for the wild type virus. The 1 unvaccinated case was positive for the wild type virus. Although the vaccine strain can reactivate and cause zoster, our data suggest that the incidence of zoster is lower in vaccinated children than in unvaccinated children, which is consistent with previously published findings.

Zoster with dissemination or complications (other than postherpetic neuralgia) in persons of any age is also reportable; 89 such cases were reported, and 83 were hospitalized. Cases ranged from 13 to 92 years of age, with a median age of 61. Fifty-six (63%) had comorbidities or were being treated with immunosuppressive drugs. Thirty-three had disseminated rash or disease, 31 had meningitis, 20 had cellulitis or other bacterial superinfection, 4 had encephalitis, 1 had meningioencephalitis, 11 had Ramsay-Hunt Syndrome, and 2 had pneumonia. Cases with disseminated rash or disease tended to be older than cases with meningitis without dissemination (median age of 62 vs. 44 years), and were more likely to have immunocompromising conditions or immunosuppressive drug treatment (83% vs. 46%). Four deaths occurred, 2 had meningitis, 1 had meningitis and Ramsay-Hunt Syndrome, and 1 had cellulitis or other bacterial superinfection. All deaths were in cases ≥50 years of age. Fifteen percent of cases ≥50 years of age had received zoster vaccine.

• For up to date information see>> Varicella (Chickenpox), Shingles (Herpes Zoster)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2018