Varicella  
Annual Summary of Reportable Diseases

Varicella, also known as chickenpox, is caused by the varicella-zoster virus. It is highly contagious and typically causes an itchy, blister-like rash, but can cause serious illness. In 2022, 204 varicella cases were reported (3.6 per 100,000 population). One hundred and nine cases (53%) were from the metropolitan area. Case ages ranged from 92 days to 66 years. Twenty-eight cases (14%) were <1 year, 78 (38%) were 1-6 years, 41 (20%) were 7-12 years, 11 (5%) were 13-17 years, and 46 (23%) were ≥18 years of age. Five cases were hospitalized; one was 1-6 years, one was 7-12 years, one was 13-17 years, and two were >18 years. Three of the hospitalized cases had not been vaccinated; one was born outside of the United States, one case due to parental refusal, and one for unknown reasons. The other two hospitalized cases had been vaccinated.

Varicella cases are often identified by parents/guardians reporting to schools and childcare facilities, rather than directly reported by a clinician. In 2022, 153 cases (75%) had visited a health care provider, 12 (6%) had consulted a provider or clinic by telephone, five (2%) had been identified by a school health professional, and 34 (17%) had not consulted a health care provider. Of the 104 cases for which information regarding laboratory testing was available, 98 (94%) had appropriate testing performed.

Two outbreaks, defined as ≥5 cases in the same setting, were reported in 2022. One outbreak occurred in a household setting and included 6 cases, one of which was unvaccinated due to being born outside of the United States. One outbreak occurred in a daycare setting and included 5 cases, four of which were unvaccinated due to being underage (first dose recommended at age 12-15 months) and one of which was unvaccinated due to parental refusal.

Zoster cases in children <18 years of age are reportable in Minnesota and 36 cases were reported in 2022. Cases may be reported by school health personnel, childcare staff, or healthcare providers. Ages ranged from 1 year to 16 years (median 5.5 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 2.7 per 100,000 population in 2022.

Zoster with dissemination or complications (other than post-herpetic neuralgia) in persons of any age is also reportable. Eight-seven of such cases were reported, of which 65 (75%) were hospitalized in 2022. Cases ranged from 16 to 95 years of age, with a median age of 62. Fifty-six (64%) had co-morbidities or were being treated with immunosuppressive drugs. Twenty-five had disseminated rash or disease, 20 had meningitis, 11 had cellulitis or other bacterial superinfection, one had pneumonia, 18 had encephalitis, one had Bells-like Palsy, 8 had meningoencephalitis, and two had Ramsay-Hunt Syndrome. Cases with disseminated rash or disease tended to be older than cases with meningitis without dissemination (median age of 64 vs. 42 years) and were more likely to have immunocompromising conditions or immunosuppressive drug treatment (76% vs. 20%). One death occurred; one had disseminated infection. The death was in a case < 65 years old. Only 20% of cases ≥50 years of age had a record of receiving zoster vaccine.

• For up to date information see: Varicella (Chickenpox)

In 2021, 169 varicella cases were reported (3.0 per 100,000 population). Ninety-seven cases (57%) were from the metropolitan area. Case ages ranged from 95 days to 69 years. Thirty-two cases (19%) were < 1 year, 73 (43%) were 1-6 years, 36 (21%) were 7-12 years, 10 (6%) were 13-17 years, and 18 (11%) were ≥ 18 years of age. Four cases were hospitalized; 1 was < 1 year, one was 1-6 years, and 2 were >18 years. Two of the hospitalized cases had not been vaccinated; one had medical contraindications, and one was underage for vaccination. The vaccination status of the other two hospitalized cases was not available.

Varicella cases are often identified by parents/guardians reporting to schools and childcare facilities, rather than directly reported by a clinician. In 2021, 108 cases (64%) had visited a health care provider, 21 (12%) had consulted a provider or clinic by telephone, 16 (10%) had been identified by a school health professional, and 24 (14%) had not consulted a health care provider. Of the 168 cases for which information regarding laboratory testing was available, 64 (38%) had appropriate testing performed.

One outbreak, defined as ≥5 cases in the same setting, was reported in 2021. This occurred in an infant room at a daycare center and included 5 cases, 4 of which were unvaccinated due to being underage (first dose recommended at age 12-15 months).

Zoster cases in children <18 years of age are reportable in Minnesota; 34 cases were reported in 2021. Cases may be reported by school health personnel, childcare staff, or healthcare providers. Ages ranged from 10 months to 16 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 2.6 per 100,000 population in 2021.

Zoster with dissemination or complications (other than post-herpetic neuralgia) in persons of any age is also reportable; 56 such cases were reported, and 44 (79%) were hospitalized. Cases ranged from 2 to 94 years of age, with a median age of 60. Thirty-seven (66%) had co-morbidities or were being treated with immunosuppressive drugs. Fourteen had disseminated rash or disease, 17 had meningitis, 11 had cellulitis or other bacterial superinfection, 8 had encephalitis, 3 had meningoencephalitis and 7 had Ramsay-Hunt Syndrome. Cases with disseminated rash or disease tended to be older than cases with meningitis without dissemination (median age of 63 vs. 43 years) and were more likely to have immunocompromising conditions or immunosuppressive drug treatment (64% vs. 27%). Five deaths occurred; two had encephalitis, two had meningoenchephalitis, and one had meningitis and Ramsay Hunt Syndrome. All deaths were in cases > 65 years. Only 19% of cases ≥50 years of age had a record of receiving zoster vaccine.

• For up to date information see:  Varicella (Chickenpox) and Shingles (Herpes Zoster)

In 2020, 125 varicella cases (2.1 per 100,000 population) were reported. Eighty cases (64%) were from the metropolitan area. Cases ranged from 103 days to 72 years of age. Sixteen cases (13%) were <1 year, 45 (36%) were 1-6 years, 25 (20%) were 7-12 years, 10 (8%) were 13-17 years, and 29 (23%) were ≥18 years of age. Four cases were hospitalized; 3 were 1-6 years, and 1 was >18 years. None of the hospitalized cases had been vaccinated; 2 had medical contraindications, 1 was an adult who had never been offered the vaccine, and 1 did not have this information available.

Varicella cases are often identified by parents/guardians reporting to schools and childcare facilities, rather than directly reported by a clinician. Of the 124 cases for which information regarding diagnosis was available, 82 (66%) had visited a health care provider, 20 (16%) had consulted a provider or clinic by telephone, 5 (4%) had been identified by a school health professional, and 17 (14%) had not consulted a health care provider. Of the 124 cases for which information regarding laboratory testing was available, 56 (45%) had appropriate testing performed (including PCR, DFA and culture).

One outbreak, defined as ≥5 cases in the same setting, was reported in 2020. This occurred in a private school and included 5 cases, all of which were unvaccinated. Three were not vaccinated due to parental refusal, 1 was underage for vaccination and 1 did not have vaccine status information available.

Zoster cases in children <18 years of age are reportable in Minnesota; 27 cases were reported in 2020. Cases may be reported by school health personnel, child care staff, or healthcare providers. Ages ranged from 1 to 17 years (median 8 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 2.1 per 100,000 population in 2020.

Zoster with dissemination or complications (other than post-herpetic neuralgia) in persons of any age is also reportable; 70 such cases were reported and 56 (80%) were hospitalized. Cases ranged from 17 to 92 years of age, with a median age of 68. Fifty-four (77%) had comorbidities or were being treated with immunosuppressive drugs. Thirty-three had disseminated rash or disease, 9 had meningitis, 20 had cellulitis or other bacterial superinfection, 12 had encephalitis, 8 had meningoencephalitis, 3 had Ramsay-Hunt Syndrome, 1 had pneumonia and 1 had myelitis. Cases with disseminated rash or disease tended to be older than cases with meningitis without dissemination (median age of 69 vs. 37 years) and were more likely to have immunocompromising conditions or immunosuppressive drug treatment (85% vs. 38%). Five deaths occurred; two had encephalitis, one had encephalitis and disseminated infection, one had pneumonia and disseminated infection, and one had meningoencephalitis and cellulitis or other bacterial superinfection. All deaths were in cases >65 years. Thirty-three percent of cases ≥50 years of age had a record of receiving zoster vaccine.

• For up to date information see: Varicella (Chickenpox) and Shingles (Herpes Zoster)

In 2019, 366 varicella cases (6.5 per 100,000 population) were reported. Two hundred ten (57%) were from the metropolitan area. Cases ranged from 28 days to 66 years of age. Fortyfour cases (12%) were <1 year, 123 (34%) were 1-6, 89 (24%) were 7-12, 40 (11%) were 13-17, and 70 (19%) were ≥18 years of age. Nine cases were hospitalized; 3 were <1 year, 1 was 1-17, and 5 were ≥18 years. Eight of the hospitalized cases had never been vaccinated; 3 were underage for vaccination, and the other 5 were adults who had never been offered the vaccine.

Varicella cases are often identified by parents/guardians reporting to schools and childcare facilities, rather than directly reported by a clinician. Of the 366 cases for which information regarding diagnosis was available, 264 (72%) had visited a health care provider, 18 (5%) had consulted a provider or clinic by telephone, 2 had been identified by a school health professional, and 82 (22%) had not consulted a health care provider. Of the 361 cases for which information regarding laboratory testing was available, 150 (41%) had appropriate testing performed. Seventeen percent of cases occurred as part of an outbreak, defined as ≥5 cases in the same setting. Four outbreaks occurred in schools. Three were private schools, and one was a public school. The largest outbreak had 8 cases; 1 case was partially vaccinated, 1 case had an unknown vaccination status, and 6 cases were unvaccinated. Of the unvaccinated cases, 4 were due to parental refusal, and 2 were unknown.

Zoster cases in children <18 years of age are reportable in Minnesota; 58 cases were reported in 2019. Cases may be reported by school health personnel, child care staff, or healthcare providers. Ages ranged from 1 to 17 years (median 9 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 4.5 per 100,000 population in 2019.

Zoster with dissemination or complications (other than postherpetic neuralgia) in persons of any age is also reportable; 80 such cases were reported, and 66 were hospitalized. Cases ranged from 13 to 99 years of age, with a median age of 56. Forty-six (58%) had comorbidities or were being treated with immunosuppressive drugs. Twenty-six had disseminated rash or disease, 27 had meningitis, 20 had cellulitis or other bacterial superinfection, 9 had encephalitis, 3 had meningioencephalitis, and 6 had Ramsay-Hunt Syndrome. Cases with disseminated rash or disease tended to be older than cases with meningitis without dissemination (median age of 66 vs. 43 years), and were more likely to have immunocompromising conditions or immunosuppressive drug treatment (77% vs. 30%). Three deaths occurred; one had encephalitis and a disseminated infection, one had meningoencephalitis, and one had a disseminated infection. All deaths were in cases >65 years. Fifteen percent of cases ≥50 years of age had a record of receiving zoster vaccine.

• Find up to date information: Varicella (Chickenpox) and Shingles (Herpes Zoster)

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) and Shingles (Herpes Zoster)

• Archive of Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health
  Archive of past summaries (years prior to 2023 are available as PDFs).