These FAQs and data dictionary terms relate to the COVID-19 surveillance dashboard.
1. Why do the number of positive COVID-19 cases change on past dates?
The data sources we use are dynamic, which means they are routinely updated. Marin County Public Health receives reports of positive COVID-19 cases thru CalREDIE, the state’s electronic lab reporting (ELR) system. There are significant delays in CalREDIE reporting (approximately 4-7 days) especially from private labs. Labs are processing high volumes of tests daily and are not reporting same-day results. There are also delays due to the need for manual entry of faxed laboratory results. Data is updated daily as CalREDIE information is updated. Cases can be reassigned to the county of residence or have status changed from suspected to confirmed, which results in a change of case counts.
2. Why does the daily increase in the cumulative case count not always align with the daily positive cases reported?
You may notice that the number of new cases from day to day does not match the cumulative total of cases reported. Marin County Public Health has implemented quality control measures to ensure accuracy. For example epidemiologists de-duplicate data, including repeat tests, multiple reports, and corrected residency status (e.g., corrected home address). All official case counts for COVID-19 are based on county of residence.
The daily cumulative case count reflects new cases that were reported to Marin County Public Health since yesterday. New cases reported to us on a given day may have been tested at an earlier date. In comparison, the daily positive cases chart shows the number of cases identified by date someone was tested for COVID-19. This date estimates the day symptoms began, which helps us understand the timing of the spread of the virus in our community. Click here to watch a video of one Marin County's Epidemiologists explaining the difference between testing date and report date.
3. Why are the number of negative tests so low for the most recent 4-7 days?
While there are reporting delays (see question 1 & 2), reporting positive test results are prioritized by labs to assist in contact tracing and case investigation. Therefore positive test results are often reported sooner than negative test results. In many cases, negative tests results are reported into CalREDIE via electronic lab reporting, which may be delayed due to a high volume of tests.
4. Why is some data on the website for residents only and other data is for a broader population?
For some factors, we want to understand our county’s service capacity and needs. For example, we test non-residents who work in Marin County providing essential services (e.g., work as care providers in nursing homes or are first responders). For other measures, such as the number of cases in our community, we only look among Marin residents as it helps us understand how those who live in Marin County are impacted by this disease.
5. Why are COVID-19 cases, hospitalizations and deaths from San Quentin State Prison reported separately from the total case count for Marin County?
COVID-19 cases occurring in the community have different implications for community spread and health department contact tracing and investigation compared to cases occurring in San Quentin State Prison. Including cases that occur in San Quentin State Prison in our overall case counts may mask our ability to identify significant trends in community transmission. Tracking both indicators is important for understanding COVID-19 impacts among all of our community members, including hospital capacity, and to appropriately tailor prevention, outreach, and treatment to each setting. COVID-19 cases occurring in San Quentin State Prison are formally under the jurisdiction of the State of California and the California Department of Corrections. Marin County supports and collaborates with San Quentin State Prison during outbreak responses at their request. For up to date information on COVID-19 in state run correctional facilities please visit the CDCR Population COVID-19 Tracking Report.
Cumulative hospitalizations of San Quentin State Prison inmates hospitalized for COVID-19 at MarinHealth, Kaiser Hospital or Novato hospital will be counted separately from cumulative hospitalizations of Marin residents living in the community. Tracking the indicators separately allows for a greater understanding of COVID-19 impacts among all our community members. Daily hospital census counts include both community and San Quentin cases as it is a measure of hospital capacity. Daily hospitalization census data is primarily used to monitor impacts of COVID-19 on hospital capacity, whereas cumulative hospitalizations overtime help us under the community impacts as a result of COVID-19.
Deaths resulting from COVID-19 at San Quentin will also not be included in the cumulative total death count for Marin residents.
6. Why do increases in the daily hospital census (“Current COVID-19 hospitalizations”) not always align with the count of residents hospitalized for COVID-19 (“Weekly COVID-19 Hospitalizations and Deaths”).
There are a few reasons why increases in the daily hospital COVID-19 census do not align with the count of residents hospitalized for COVID-19:
- These are two different measurements coming from two different data sources– count of residents hospitalized for COVID-19 is calculated using Marin HHS’ contact investigation database to determine cases of Marin County residents who have been hospitalized for COVID-19. The “Current COVID-19 hospitalizations” and hospital census & ICU chart come from a daily poll conducted by California Department of Public Health (CDPH) where hospitals provide the count of COVID-19 patients in their hospital on that day. Daily hospitalization census data is primarily used to monitor impacts of COVID-19 on hospital capacity, whereas cumulative hospitalizations overtime help us under the community impacts as a result of COVID-19.
- Resident status – Finally, not all people counted in the daily hospital census are Marin county residents. CDPH daily census data can include out of county residents that are not included in the count of Marin residents hospitalized for COVID-19. For example, if someone who lives outside of Marin County was hospitalized at a Marin County Hospital they would be captured in the CDPH daily COVID-19 census (helping us understand hospital capacity), but not in the count of Marin residents hospitalized for COVID-19. Likewise, if a Marin resident was hospitalized in another county, that hospitalization would be included in the count of Marin residents hospitalized for COVID-19 but would be reflected in the daily COVID-19 hospital census.
- Reporting delay- if someone enters the hospital on 6/15 it may take 4-10 days for that hospitalization to be reported to Marin HHS and entered into Marin HHS’ contact investigation database. For example, if the daily hospitalization census jumps from 2 to 6 people from 6/8 to 6/9 it may not be reflected in the count of total hospitalizations until 6/12.
- Quality Assurance – MarinHHS actively engages in QI efforts to insure COVID-19 data is being accurately reported to the public. On occasion this may mean that data needs to be updated to reflect new guidance or to address any data entry errors.