Outbreak Investigations At A Glance
Possible Multistate Outbreaks
This analysis includes 135 investigations of possible multistate enteric (intestinal) outbreaks during 2021. Some possible outbreaks were excluded from this report because they were determined to be single state or because they were linked to international travel. After investigation, 74 (55%) of these were determined to be multistate outbreaks, and investigators solved 47 (64%) of these outbreaks.
Multistate Outbreaks
The number of outbreaks increased from 2020 but was lower than the 82 investigated outbreaks in 2019. The number of outbreaks investigated in 2021 was likely lower than that in 2019 due in part to continued effects of the COVID-19 pandemic on enteric disease outbreak detection and investigation (e.g., decreased resources at local, state, and federal public health agencies, changes in healthcare-seeking behavior, and changed restaurant dining and grocery shopping patterns.) Additionally, changing diagnostic testing practices likely continued to affect enteric disease surveillance and the ability to identify possible outbreaks.
Solved Multistate Outbreaks
Among the 74 multistate outbreaks, 47 (64%) were solved, meaning a confirmed or suspected source of the outbreak was identified, including 25 (53%) outbreaks with confirmed sources and 22 (47%) with suspected sources. Among the 47 solved outbreaks, 28 (60%) were linked to contaminated foods, and 19 (40%) were linked to animal contact.
Solved multistate outbreaks caused at least 2,047 illnesses. Solved multistate outbreaks linked to contaminated food caused 1,740 illnesses, 496 hospitalizations, and 15 deaths, while multistate outbreaks linked to animal contact caused 1,307 illnesses, 329 hospitalizations, and 3 deaths.
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