Reportable Medical Events (RMEs) are documented in the Disease Reporting System internet (DRSi) by health care providers and public health officials throughout the Military Health System (MHS) for monitoring, controlling, and preventing the occurrence and spread of diseases of public health interest or readiness importance. These reports are reviewed by a team of validators from Defense Centers for Public Health (DCPH). The DRSi collects reports on over 70 different RMEs, including infectious and non-infectious conditions, outbreak reports, sexually transmitted infection (STI) risk surveys, and tuberculosis contact investigation reports. A complete list of RMEs is available in the 2022 Armed Forces Reportable Medical Events Guidelines and Case Definitions.¹ Data reported in these graphs and table are considered provisional and do not represent conclusive evidence until case reports are fully validated.

Total active component cases reported per week are displayed for the 5 most frequently reported RMEs for the prior year, or preceding 52 weeks. Each quarter, the graph is updated and presented with the quarter’s (Q1, 2026) 5 most frequently reported RMEs, which may differ from those of previous quarters.

DRSi requires the reporting of numerous gastrointestinal (GI) illnesses.¹ In Q1 2026, the most frequently reported GI illnesses among U.S. active component service members were cryptosporidiosis, norovirus, and campylobacteriosis. An outbreak of cryptosporidiosis occurred in the Republic of Korea (ROK), with most cases reported in January and February 2026, which contributed to a much larger number of reports of cryptosporidiosis in Q1 2026 compared to the entire calendar year of 2025. The number of reports for norovirus in DRSi were lower in January and March 2026 than in their respective months in 2025, while the number of norovirus reports in February 2026 was slightly higher than February 2025. Additionally, campylobacteriosis reports in DRSi during the months of Q1 2026 remained similar to the number of reports seen in the months of Q1 2025.

DCPH-A developed the Communicable Disease Toolkit to provide guidance for reporting RME cases and outbreaks to DRSi.² Tools such as investigation worksheets and case definition flowcharts are available in the Communicable Disease Toolkit for all RMEs, including reportable GI illnesses.

For questions about this report, please contact the Disease Epidemiology Branch at the Defense Centers for Public Health–Aberdeen. Email: dha.apg.pub-health-a.mbx.disease-epidemiologyprogram13@health.mil

References

1. Armed Forces Health Surveillance Division. Armed Forces Reportable Medical Events Guidelines and Case Definitions. Defense Health Agency, U.S. Dept. of War. 2022. Accessed Feb. 28, 2024. https://health.mil/reference-center/publications/2022/11/01/armed-forces-reportable-medical-events-guidelines 
2. Defense Health Agency–Public Health. Communicable Disease Toolkit. Health.mil. U.S. Dept. of War. Updated Apr. 14, 2025. Accessed Jul. 28, 2026. https://ph.health.mil/topics/healthsurv/de/Pages/cdt.aspx

Authors’ Affiliation

Defense Health Agency, Disease Epidemiology Branch, Defense Centers for Public Health–Aberdeen