Varicella and Zoster, 2017

In 2017, 432 varicella cases (8.0 per 100,000 population) were reported, the highest incidence since 2013. Two hundred ninety-seven (69%) were from the metropolitan area. Cases ranged from 7 weeks to 85 years of age. Sixty-one cases (14%) were <1 year, 170 (39%) were 1-6 years, 99 (23%) were 7-12 years, 29 (7%) were 13-17 years, and 73 (17%) were ≥18 years of age. Nine cases were hospitalized; 1 was 9 months, 2 were 5-14 years, and 6 were >24 years of age. Four had severe disease and/or complications including pneumonia, viral labyrinthitis, bacterial superinfection, and dehydration. One was immunocompromised and 2 had a co-morbidity. Seven had never received varicella-containing vaccine; 4 were adults who had never been offered the vaccine, 1 had a history of previous disease, 1 was underage for vaccination, and 1 was unvaccinated due to parental refusal. One case who was immunocompromised had been vaccinated with 1 dose of varicella vaccine, and 1 case had unknown history of vaccination. There were no varicella-related deaths.

Varicella cases are often identified by parents/guardians reporting to schools and child care facilities, rather than directly reported by a clinician. Of the 430 cases for which information regarding diagnosis was available, 313 (73%) had visited a health care provider, 28 (7%) had consulted a provider or clinic by telephone, 7 (2%) had been identified by school health personnel, and 82 (19%) had not consulted a health care provider. Of the 320 cases for which information regarding laboratory testing was available, 153 (36%) had testing performed. Eleven percent of cases occurred as part of an outbreak, defined as ≥5 cases in the same setting. Three outbreaks occurred in schools. All were charter or private schools offering grades K though 9 or higher. Two outbreaks included several sets of unvaccinated siblings. The largest outbreak had 21 cases; 3 cases were fully vaccinated, and 18 were unvaccinated. Of the unvaccinated cases, 10 were due to parental refusal; 8 were unknown because a parent interview could not be obtained. Two outbreaks occurred in the infant rooms of child care centers; each had 9 cases, all of whom were too young to be vaccinated. In one outbreak, hand, foot and mouth disease was clinically diagnosed  or  suspected by health care providers of several cases; specimens from 5 cases were submitted by parents using kits supplied by MDH for further characterization. All 7 cases tested positive for VZV by PCR, and all 5 specimens tested at MDH were negative for enteroviruses by PCR.

Zoster cases in children <18 years of age are reportable; 77 cases were reported. Cases may be reported by school health personnel, child care staff, or healthcare providers. Ages ranged from 10 months to 17 years (median 11 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 6.0 per 100,000 population in 2017. In 2017, the PHL performed strain typing on specimens from 28 zoster cases. Of the 23 vaccinated cases, 20 (87%) were positive for the vaccine strain and 3 (13%) were positive for the wild type virus. All 5 unvaccinated cases were 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 which is consistent with previously published findings.

Zoster with dissemination or complications (other than post- herpetic neuralgia) in persons of any age is also reportable; 65 such cases were reported, and 59 were hospitalized. Cases ranged from 15 to 93 years of age, with a median age of 61. Thirty-nine (60%) had co-morbidities or were being treated with immunosuppressive drugs. Twenty-nine had disseminated rash or disease, 18 had meningitis, 8 had cellulitis or other bacterial superinfection, 5 had encephalitis, 9 had Ramsay-Hunt Syndrome, 2 had Bell-like palsy, and 1 had pneumonia. Cases with disseminated rash or disease tended to be older than cases with meningitis without dissemination (median age of 68 vs. 44 years), and were more likely to have immunocompromising conditions or immunosuppressive drug treatment (82% vs. 15%). Two deaths occurred, 1 with encephalitis, and 1 with disseminated disease. Twenty-four percent of cases ≥60 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, 2017