What Happened to Major Outbreaks of Severe Diarrheal Illness (2024-2026)?

The period from 2024 to mid-2026 has been marked by a series of significant and often severe diarrheal illness outbreaks across the globe, highlighting persistent public health challenges and the impact of environmental and societal factors.

Global Cholera Crisis Continues: The seventh cholera pandemic, which intensified globally since 2022, continued its alarming trajectory. In 2024, 60 countries reported cases, an increase from 45 in 2023, with 560,823 cases and 6,028 deaths reported globally, though these figures likely underestimate the true burden. The burden remained concentrated in Africa, the Middle East, and Asia, accounting for 98% of all reported cases. These trends persisted into 2025, with a cumulative total of 614,828 cholera cases and 7,598 deaths reported from 33 countries by late December 2025. As of June 22, 2026, 105,813 cholera cases and 1,216 deaths have been reported worldwide since January 1, 2026. The World Health Organization (WHO) considers the global risk from cholera as very high, with extreme climate events, poverty, and conflict compounding the problem and leading to shortages of cholera tools, including vaccines. Efforts to combat the crisis emphasize integrated Water, Sanitation, and Hygiene (WASH) interventions alongside vaccination.

Norovirus Activity: Norovirus, a leading cause of acute gastroenteritis, showed increased activity in the United States. The 2024-2025 seasonal year saw an early surge, with 495 outbreaks reported by NoroSTAT-participating states from August 1 to December 11, 2024, exceeding previous seasonal ranges. A new dominant strain, GII.17, accounted for approximately 75% of outbreaks in the 2024-2025 season. While the 2025-2026 season, as of June 11, 2026, reported 1,287 outbreaks, which is within the typical interquartile range, norovirus remains a frequent cause of foodborne illness, often linked to infected food workers and contaminated produce or shellfish.

E. coli Outbreaks Linked to Food: Several E. coli outbreaks were reported, primarily linked to contaminated food products. In October 2024, an E. coli outbreak was linked to onions served at McDonald's, affecting over 100 individuals across 14 states. Another outbreak in May 2024 was tied to organic walnuts. A significant multistate E. coli O157:H7 outbreak linked to Raw Farm brand raw dairy products, specifically raw cheddar cheese, occurred between September 2025 and February 2026, affecting at least 9 people in 3 states, with 3 hospitalizations. Notably, Raw Farm declined the FDA's recommendation for a voluntary recall, leading to public health advisories to discard the product. As of May 2026, another E. coli O157:H7 outbreak sickened nine California residents, with five hospitalizations and two cases of hemolytic uremic syndrome (HUS).

Rotavirus Resurgence: Rotavirus, a severe threat to infants and young children, experienced a surge in cases across the United States in early 2026. Data from January to April 2026 showed positivity rates higher than the 2025 seasonal peak, with wastewater monitoring also indicating elevated levels. Experts attribute this rise partly to declining rotavirus vaccination rates, which have steadily decreased over the past eight years, with national completion rates in the low-to-mid 70 percent range in 2024-2025. A rotavirus A outbreak also occurred at a federal university campus in Southern Brazil in late September 2024, affecting over 200 students and suggesting a probable waterborne transmission route.

Cyclosporiasis Spike in 2026: As of July 2, 2026, the Centers for Disease Control and Prevention (CDC) is tracking a seasonal spike in cyclosporiasis cases in the United States. Between May 1 and June 16, 2026, 145 cases were reported across 17 states, resulting in 20 hospitalizations. While no single multistate outbreak has been identified, investigations into potential clusters and sources are ongoing. Cyclosporiasis, caused by the parasite Cyclospora cayetanensis, is typically acquired through contaminated food or water, with fresh produce often implicated during the spring and summer months.