​The national Council of State and Territorial Epidemiologists (CSTE) recently posted Proposed Investigation/Reporting Thresholds and Outbreak Definition for COVID-19 in Healthcare Settings (PDF). These thresholds are intended to expedite facilities' investigation of COVID-19 cases and reporting to public health authorities, to help ensure early detection of possible outbreaks and timely intervention to prevent the virus' spread. Reporting of outbreaks and unusual infectious disease occurrences does not replace reporting of individual COVID-19 cases as part of state and local COVID-19 surveillance nor daily reporting for upload on their behalf to the National Healthcare Safety Network (NHSN).[1] When the reporting threshold is reached and reported, LHDs will determine if the cases constitute an outbreak.

Acute Care Hospitals:
Threshold for Additional Investigation by Facility

• ≥1 case of confirmed COVID-19 in a patient 7 or more days after admission for a non-COVID condition;
• ≥1 case of confirmed COVID-19 in Healthcare Personnel (HCP)

Threshold for Reporting to Local Public Health

• ≥2 cases of confirmed COVID-19 in a patient 7 or more days after admission for a non-COVID condition, with epi-linkage[2];
• ≥2 cases of confirmed COVID-19 in HCP with epi-linkage[3] in counties with <4 daily new cases per 100k population or <5% test positivity based on the county positivity rate reported in the past week[4], or
• ≥3 cases of confirmed COVID-19 in HCP with epi-linkage3 in counties with ≥4 daily new cases per 100k population or ≥5% test positivity based on the county positivity rate reported in the past week[4].

Outbreak Definition

• ≥2 cases of confirmed COVID-19 in a patient 7 or more days after admission for a non-COVID condition, with epi-linkage[2];
• ≥2 cases of confirmed COVID-19 in HCP with epi-linkage[3] who do not share a household, and are not listed as a close contact of each other outside of the workplace during standard case investigation or contact tracing in counties with <4 daily new cases per 100k population or <5% test positivity based on the county positivity rate reported in the past week[4], or
• ≥3 cases of confirmed COVID-19 in HCP with epi-linkage[3] who do not share a household, and are not listed as a close contact of each other outside of the workplace during standard case investigation or contact tracing in counties with ≥4 daily new cases per 100k population or ≥5% test positivity based on the county positivity rate reported in the past week[4].

The determination of epi-linkage should generally be made irrespective of whether HCP were wearing a respirator or facemask. Although respirator or facemask use mitigates the risk of exposures, a cluster of cases meeting the investigation and reporting thresholds suggests a breach or lapse in practice (for example, HCP not using appropriate personal protective equipment while caring for a patient with unrecognized COVID-19, or HCP not physically distancing and wearing facemasks in breakrooms) that should be further investigated and reported.

Long-Term Care Facilities and Long-Term Acute Care Hospitals:

Threshold for Additional Investigation by Facility

• ≥1 probable[5] or confirmed COVID-19 case in a resident or HCP;
• ≥3 cases of acute illness compatible with COVID-19 in residents with onset within a 72-hour period

Threshold for Reporting to Local Public Health

• ≥1 probable[5] or confirmed COVID-19 case in a resident or HCP;
• ≥3 cases of acute illness compatible with COVID-19 in residents with onset within a 72-hour period

Outbreak Definition

• ≥1 facility-acquired[6] COVID-19 case in a resident

For additional information on the identification and response to COVID-19 cases please refer to Investigation of COVID-19 Outbreaks in Acute Care Hospitals (PDF). This document was developed by CDPH Healthcare Associated Infections (HAI) Program in accordance with CDC guidance on Responding to SARS-CoV-2 Infections in Acute Care Facilities. 

If you have any questions about this AFL, please contact the CDPH Healthcare-Associated Infections Program via email at HAIProgram@cdph.ca.gov.   

Sincerely,

Original signed by Cassie Dunham

Cassie Dunham

Acting Deputy Director

Resources:

• Proposed Investigation/Reporting Thresholds and Outbreak Definition for COVID-19 in Healthcare Settings (PDF)
• Tracking COVID-19 in California - Coronavirus COVID-19 Response
• Investigation of COVID-19 Outbreaks in Acute Care Hospitals (PDF)
  

[1] CDPH collects data from skilled nursing facilities and hospitals daily and transmits data to NHSN on behalf of those facilities that have conferred rights to CDPH.

[2] Epi-linkage among patients is defined as overlap on the same unit or ward for any duration or having the potential to have been cared for by common HCP within a 14-day time period of each other.

[3] Epi-linkage among HCP is defined as having the potential to have been within 6 feet for 15 minutes or longer while working in the facility during the 14 days prior to the onset of symptoms or positive test (for example, worked on the same unit during the same shift). 

[4] Facilities and LHDs should refer to the Tracking COVID-19 in California - Coronavirus COVID-19 Response for their county's daily new cases per 100k population and percent test positivity.

[5] Probable case is defined as any one of the following: a person meeting clinical criteria AND epidemiologic evidence with no confirmatory laboratory testing performed for COVID-19; a person meeting presumptive laboratory evidence AND either clinical criteria OR epidemiologic evidence; a person meeting vital records criteria with no confirmatory laboratory testing performed for COVID-19.

[6] Facility-acquired COVID-19 infection in a long-term care resident is defined as a confirmed diagnosis 14 days or more after admission for a non-COVID condition, without an exposure during the previous 14 days to another setting where an outbreak was known or suspected to be occurring.