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State of California—Health and Human Services Agency
California Department of Public Health

AFL 23-08
January 18, 2023

General Acute Care Hospitals (GACH)
Skilled Nursing Facilities (SNF)

Requirements to Report Outbreaks and Unusual Infectious Disease Occurrences 
(This AFL supersedes AFL 19-18)

​AUTHORITY:     Title 42 Code of Federal Regulations (CFR) section 482.42

                                Title 17 California Code of Regulations (CCR) sections 2500-2502,  

                                Title 22 CCR sections 70737, 70739, 72523, 72539, and 72541

​All Facilities Letter (AFL) Summary

This AFL reminds providers of the requirements to report outbreaks and unusual infectious disease occurrences to the local public health officer and the California Department of Public Health (CDPH) and provides definitions and updated examples of reportable incidents. 

​Health facilities licensed by CDPH Licensing and Certification (L&C) are required to report outbreaks and unusual infectious disease occurrences to the local public health officer and their respective District Office (DO). To account for changes in the local epidemiology of some multidrug-resistant organisms (MDRO), this AFL revises examples of incidents that should be reported relative to the usual frequency of the MDRO in the same facility, region or local health jurisdiction (LHJ). Facilities should consult with their LHJ for information about the local epidemiology of a given MDRO to determine whether incidents should be reported. In addition, this AFL refers to recommended pathogen-specific outbreak reporting thresholds, definitions and other resources provided by the Council for Outbreak Response – Healthcare-Associated Infections and Antimicrobial Resistance (CORHA), where available.


Outbreak - The occurrence of cases of a disease or condition above the expected or baseline level, usually over a given period of time, in a geographic area or facility, or in a specific population group. The number of cases indicating the presence of an outbreak will vary according to the disease or agent, size and type of population exposed, previous exposure to the agent, and the time and place of occurrence. Thus, the designation of an outbreak is relative to the usual frequency of the disease or condition in the same facility or community, among the specified population, over a comparable period of time. For example, a single case of a communicable disease long absent from a population or the first invasion by a disease not previously recognized requires immediate reporting and epidemiologic investigation.

Unusual Disease - A rare disease or a newly apparent or emerging disease or syndrome of uncertain etiology which a health care provider has reason to believe could possibly be caused by a transmissible infectious agent or microbial toxin.

Unusual Occurrences - Occurrences such as epidemic outbreaks, poisonings, fires, major accidents, death from unnatural causes or other catastrophes and unusual occurrences which threaten the welfare, safety or health of patients, personnel or visitors.

Examples of Reportable Incidents:

CDPH is aware that licensed facilities are interpreting these requirements differently. To improve understanding and consistency applying the requirements, CDPH provides the following examples of outbreaks or unusual infectious disease occurrences that should be reported, acknowledging that the determination of whether an incident meets the definition of an outbreak or unusual infectious disease occurrence may be relative to the usual frequency of the condition in the same facility, region, or LHJ:

  • Single case of colonization or infection with an MDRO if it was never previously or only rarely encountered in the facility, region or LHJ, such as Candida auris or a specific carbapenemase-producing organism (CPO), depending on the facility, region or LHJ;
  • Outbreak or increased incidence of any MDRO, such as methicillin-resistant S. aureus (MRSA) colonization or infection in a neonatal intensive care unit (NICU), or a specific CPO in a long-term care facility; in facilities or regions where a specific MDRO is considered endemic (PDF), this may be an increase in new cases above the baseline;
  • Single case of presumptive healthcare-associated Legionnaires' disease;
  • Single case of postpartum or post-surgical or facility outbreak of healthcare-associated invasive group A beta-hemolytic Streptococcus;
  • Outbreak or increased incidence of any infectious agent, device- or procedure-associated infection, such as an increase in cases of patients with cultures positive for Burkholderia in an intensive care unit, or a case of post-operative or post-procedure extrapulmonary nontuberculous mycobacteria infection;
  • Facility outbreak of COVID-19, influenza, pneumonia, other respiratory viral pathogen (e.g., respiratory syncytial virus), or gastroenteritis (e.g., norovirus);
  • Infections suspected to be associated with contaminated medication, transfused blood products (e.g., platelets), or other distributed medical product;
  • Foodborne infectious disease outbreak.

Outbreaks of any condition should generally be reported regardless of the results of genetic-relatedness testing (e.g., whole genome sequencing), if performed. Please note the above list is not all-inclusive. Rather, it should be used as a guide when making a determination on whether or not to report an occurrence. If in doubt, report.

Upon receipt of a report of an outbreak or unusual occurrence, the LHD recommends control actions and may conduct an epidemiologic investigation. The L&C DO makes a determination on regulatory follow-up action, which may include an onsite survey. The CDPH Healthcare-Associated Infections (HAI) Program is available to local public health authorities and L&C for consultation on infection control and containment measures.

If you have any questions, please contact your respective L&C District Office or the CDPH HAI Program at



Original signed by Cassie Dunham

Cassie Dunham

Deputy Director

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