Outbreak of Norovirus Gastroenteritis Associated With Ice Cream Contaminated by Frozen Raspberries From China-Minnesota, United States, 2016.

BACKGROUND: Norovirus is the etiology for about 60% of foodborne outbreaks identified in Minnesota. Contamination of food during preparation by food handlers is by far the most common cause of these outbreaks. Norovirus outbreaks due to commercially distributed foods are rarely reported in the United States, and only 2 have been previously identified in Minnesota, both due to oysters. METHODS: In August 2016, we investigated an outbreak of norovirus gastroenteritis in Minnesota that was linked to consumption of commercially distributed ice cream at multiple venues. Sanitarians from local public health agencies visited the facilities involved for follow-up, and case-control studies were conducted. The outbreak was identified by linking multiple independent illness reports to a centralized foodborne illness complaint system and subsequently confirmed though genotyping of stool specimens. RESULTS: A total of 15 cases from 4 venues were reported. Raspberry chocolate chip ice cream was statistically associated with illness in 2 analytic studies (6 of 7 cases vs 0 of 7 controls; odds ratio, undefined; P = .005). Norovirus GII.17[P17] (GII.17 Kawasaki) strains from case stool specimens matched norovirus found in frozen raspberries imported from China that were used to make the implicated ice cream. CONCLUSIONS: To our knowledge, this is the first norovirus outbreak due to commercially distributed frozen berries identified in the United States. To detect norovirus outbreaks associated with commercially distributed food vehicles, investigators should thoroughly investigate all norovirus outbreaks (including stool testing and genotyping), coordinate complaint and response activities across agencies and jurisdictions, and consider testing food for norovirus when appropriate.

An outbreak of measles in an undervaccinated community.

Measles is readily spread to susceptible individuals, but is no longer endemic in the United States. In March 2011, measles was confirmed in a Minnesota child without travel abroad. This was the first identified case-patient of an outbreak. An investigation was initiated to determine the source, prevent transmission, and examine measles-mumps-rubella (MMR) vaccine coverage in the affected community. Investigation and response included case-patient follow-up, post-exposure prophylaxis, voluntary isolation and quarantine, and early MMR vaccine for non-immune shelter residents >6 months and <12 months of age. Vaccine coverage was assessed by using immunization information system records. Outreach to the affected community included education and support from public health, health care, and community and spiritual leaders. Twenty-one measles cases were identified. The median age was 12 months (range, 4 months to 51 years) and 14 (67%) were hospitalized (range of stay, 2-7 days). The source was a 30-month-old US-born child of Somali descent infected while visiting Kenya. Measles spread in several settings, and over 3000 individuals were exposed. Sixteen case-patients were unvaccinated; 9 of the 16 were age-eligible: 7 of the 9 had safety concerns and 6 were of Somali descent. MMR vaccine coverage among Somali children declined significantly from 2004 through 2010 starting at 91.1% in 2004 and reaching 54.0% in 2010 (χ(2) for linear trend 553.79; P < .001). This was the largest measles outbreak in Minnesota in 20 years, and aggressive response likely prevented additional transmission. Measles outbreaks can occur if undervaccinated subpopulations exist. Misunderstandings about vaccine safety must be effectively addressed.