Varicella and Zoster, 2014

Case-based surveillance for varicella was implemented for January 1, 2013. Due to declining varicella incidence in the post-vaccination era, the sentinel school program in place from 2006 through 2012 was no longer an effective surveillance tool and was discontinued.

During 2014, 297 cases (6 per 100,000 population) were reported compared to 483 in 2013. One hundred eighty-seven cases (63%) were reported from the metropolitan area. Cases ranged from 6 weeks to 52 years of age. Thirty-six (12%) cases were <1 year of age; 96 (32%) were 1-5 years of age; 97 (33%) were 6-12 years of age; 25 (8%) were 13-17 years of age; and 43 (14%) were 18 years of age and older.

For the first time since school outbreak surveillance began in 2005, no school outbreaks were reported. Two small outbreaks were associated with child care. One occurred in a home childcare and included 2 cases who were unvaccinated for varicella due to parental refusal, 2 cases who were underage for the vaccine, and 1 case with 1 dose of varicella vaccine. The other childcare outbreak occurred in a center with a separate infant room; all 5 cases were underage for vaccination.

During 2014, 12 cases were hospitalized, but no deaths were reported. Of the hospitalized cases, 3 (25%) were <1 year of age, 5 (42%) were 1-12 years of age, and 4 (33%) were ≥13 years of age. Seven had complications including bacterial superinfection, high fever, seizures, dehydration, and tachypnea with fatigue. Only 3 of the cases had predisposing conditions for severe disease; 1 was immunosuppressed due to chemotherapy, 1 was on an immunosuppressive drug following organ transplant, and 1 had an underlying condition of eczema. Eight of the cases had never received varicella-containing vaccine; 3 were underage for the vaccine, 2 were adults who were never offered the vaccine, and 2 were unvaccinated due to parental refusal. Three cases had been vaccinated with at least 1 dose of varicella vaccine; all 3 were hospitalized for observation rather than for severe varicella rash or complications. Vaccination history was unknown for the remaining case.

Varicella is sometimes identified by parents/guardians reporting to schools and child care facilities, rather than diagnosed by a health care provider. Of the 290 cases for which information is available, 213 (73%) had visited a health care provider, 15 (5%) had consulted a provider or clinic by telephone, 2 (1%) had been identified by school health personnel, and 60 (21%) had not consulted a provider. Laboratory confirmation of varicella by PCR is recommended for confirmation when rash presents atypically and for confirmation of outbreaks. Of the 258 cases for which information regarding testing was available, 74 (29%) had some type of testing performed.

Since 2006, ACIP has recommended 2 doses of varicella vaccine for children. The Minnesota school immunization law has required 2 doses of vaccine for students entering kindergarten and grade 7 since 2010. Beginning with the 2014-15 school year, all students in grades K-12 are required to have 2 doses. Children 15 months or older who are enrolled in childcare or preschool are required to have 1 dose. Young adults should be evaluated for varicella immunity (history of varicella disease or 2 doses of varicella vaccine at least 4 weeks apart) and offered vaccine if indicated. Varicella is often more severe in adolescents and adults and poses special risks to pregnant women and newborn infants.

All zoster cases in children <18 years of age are reportable. Cases may be reported by school health personnel, childcare facilities, or health care providers. During 2014, 69 zoster cases were reported. Ages ranged from 1 to17 years (median, 11 years). Sixty-four (94%) of the 68 cases for which information about diagnosis was available had been seen by a health care provider. Among the 53 cases for whom both varicella disease history and vaccination history were available, 17 (32%) had a history of disease but had not received vaccine, 23 (43%) had no history of disease but had received 1-2 doses of vaccine, and 13 (25%) had a history of disease and had received 1-2 doses of vaccine.

Zoster with dissemination or complications (other than post-herpetic neuralgia) in persons of any age is also reportable. During 2014, 73 zoster cases with dissemination or complications were reported; 70 were hospitalized. Thirty-six cases were ≥ 60 years of age, 25 were 30 to 59 years of age, and 12 were <30 years of age. Forty-one (56%) had underlying conditions or were being treated with immunosuppressive drugs.

Twenty-nine cases had disseminated disease, 23 had meningitis, 11 had encephalitis or meningoencephalitis, 8 had cellulitis or other bacterial superinfection, 7 had pneumonia, 2 had Ramsay-Hunt Syndrome, 2 had myelitis, and 1 had dehydration. The presence of underlying conditions or treatment with immunosuppressive drugs was more common among cases with disseminated disease (93%) than among those with meningitis without disseminated rash (22%). Three cases with encephalitis subsequently died; one of these was immunocompromised.

• For up to date information see>> Varicella (Chickenpox)
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2014