OC Health Care Agency COVID-19 Data Frequently Asked Questions


Elevated Disease Transmission

Blueprint for a Safer Economy: California has a new blueprint for reducing COVID-19 in the state with revised criteria for loosening and tightening restrictions on activities. Find out how businesses and activities can open in counties statewide beginning on August 31. See the activities and business tiers. More information at: https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/COVID-19/COVID19CountyMonitoringOverview.aspx

Daily Case Rate Per 100,000: Calculated as the average (mean) daily number of COVID-19+ cases, excluding cases among persons incarcerated at state or federal prisons (identified as cases with an ordering facility name or address associated with prison locations), over 7 days (based on episode date), divided by the number of people living in the county/region/state. This number is then multiplied by 100,000. Due to reporting delays, there is a 7 day lag built into this calculation. For example, for data updated through 8/22/20, the case rate will be dated as 8/15/20 and will include the average case rate from 8/9/20 - 8/15/20.

Testing Positivity Percent: Calculated as the total number of positive polymerase chain reaction (PCR) tests for COVID-19 over a 7-day period (based on specimen collected date) divided by the total number of PCR tests conducted (excludes tests for persons out of state or with unknown county of residence), excluding tests for persons incarcerated at state or federal prisons (identified as cases with an ordering facility name or address associated with prison locations). This number is then multiplied by 100 to get a percentage. Due to reporting delay (which may be different between positive and negative tests), there is a 7-day lag. Example: For cumulative lab data received on 8/22/20, reported test positivity is dated as 8/15/20 and is calculated based on tests with specimen collection dates from 8/9/20 - 8/15/20.

Limited Hospital Capacity

Percent Intensive Care Unit (ICU) Beds Currently Available: The total number of available ICU beds divided by the total number of staffed ICU beds. This number is then multiplied by 100 to get a percentage.

Percent Ventilators Currently Available: The total number of available ventilators divided by the total number of ventilators. This number is then multiplied by 100 to get a percentage.

Confirmed Cases

Confirmed Cases: The total number of patients with laboratory confirmation of the virus causing COVID-19.

Cumulative Cases: The cumulative number of patients with laboratory confirmation of the virus causing COVID-19.

Daily COVID+ Cases Received: The number of laboratory confirmed cases received today. Note that it takes time for a person's specimen to be tested, the results logged and transmitted into the system.


Cumulative Deaths: The total number of COVID-related deaths to Orange County residents.

Daily (New) Deaths Received: The number of new deaths reported each day.

Cumulative Number of Deaths: The total number of COVID-related deaths to Orange County residents.

Number of Deaths by Data of Death: The number of COVID-related deaths presented by the decedent's date of death.


Cumulative Tests: The total number of polymerase chain reaction (PCR) tests (diagnostic tests) that have been conducted to date.

Daily Tests Received: The number of polymerase chain reaction (PCR) tests (diagnostic tests) reported on a given day.


Current Hospital Patients: The total number of patients hospitalized with a confirmed (laboratory confirmed) case of COVID-19  in an acute care hospitals for the most recent date on which data is available.

Current ICU Patients: The number of ICU beds filled by patients known to have COVID-19 (confirmed by a laboratory test) in an acute care hospitals for the most recent date on which data is available.

General Questions

What are the sources for the data?

  • Confirmed cases and testing data are from the California Reportable Disease Information Exchange, or CalREDIE. CalREDIE is a secure system that the California Department of Public Health (CDPH) has implemented for electronic disease reporting and surveillance. More information is available online at https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/CalREDIE.aspx.
  • Case demographics are from reported lab testing (if provided by the lab) and public health investigations.
  • Death data is from death certificates or gathered through the course of case investigation.
  • Hospital and intensive care unit (ICU) data are from CDPH via the California Health and Human Services Data Portal.
  • The State of California provides hospital data to the OC Health Care Agency (HCA).
  • Locally, the Emergency Medical Services (EMS) team may poll hospitals with emergency departments directly thru the ReddiNet system for time-sensitive questions. ReddiNet facilitates information exchange among hospitals, EMS, paramedics, law enforcement and other health care system professionals over a reliable and secure network. More information is available online at https://www.reddinet.com.

What is CalREDIE and why is it important when talking about data?

CalREDIE (California Reportable Disease Information Exchange) is a secure system that the California Department of Public Health has implemented for electronic disease reporting and surveillance. Laboratories submit reportable labs results to public health through CalREDIE Electronic Laboratory Reporting (ELR). More info can be found here: https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/CalREDIE.aspx 

Why are community members experiencing difficulty matching the CDPH 14-day case rate calculations using local data shared on HCA’s open data portal?

HCA doesn't calculate any of the County Monitoring Indicators. CDPH provides the indicators values to the county each day. As we state this on the first page of the dashboard: https://www.cdph.ca.gov/Programs/CID/DCDC/Pages/COVID-19/CountyMonitoringDataStep1.aspx

This analysis was based on date of specimen collection. However, CDPH uses the date of earliest episode (e.g., self-reported onset of symptoms or specimen collection date) when calculating case rates for the County Monitoring List. This is another variation in a dynamic situation that makes it very challenging to exactly match the results reported by CDPH.

How “real-time” is the data?

The hospital data provided to HCA from the State is delayed by about 24 hours. Case data reported each day has approximately a one-day delay from the time HCA receives reports from CalREDIE until reported on the website. On average, it takes two to three days from the time of specimen collection until HCA receives the report, but individual cases can vary. COVID-19 deaths are not directly reported to HCA, so it takes longer to identify and confirm deaths. Often this is done through review of death certificates, so the time from date of death until public reporting varies, but is a longer delay in most instances than case reports.

Does HCA evaluate the data to ensure it is accurate? If so, what is the process?

The hospital data is evaluated manually by an analyst to ensure there are no duplicates or gross inaccuracies. Due to the near real-time reporting of case data, all reports are preliminary and subject to change. As HCA conducts case investigations, data is verified, cleaned and corrected, as needed. Each day when the webpage data is updated, adjustments are made to provide the most accurate snapshot of all data at time of reporting.

Does HCA report on State data only, or are there data points that are specific and unique to CA? If so, what are those data points and where are they coming from?

HCA relies on State data for the hospital data points. Case data is gathered through local disease reporting and case investigation.

How many hospitals are reflected in the data?

There are 33 hospitals reflected in the data that is obtained from the California Health and Human Services Data Portal. https://data.chhs.ca.gov/dataset/california-covid-19-hospital-data-and-case-statistics.

I’ve heard 26 hospitals, 33 hospitals. Which is it and why is there a difference?

We are using CDPH’s data on all 33 hospitals to report hospital and ICU cases on our website. It is important to note that there are 26 acute hospitals with emergency rooms and 7 subacute hospitals without, here in Orange County.

Why are skilled nursing facilities (SNFs), jails, and homeless shelters broken out specifically but other congregate facilities are not?

Pursuant to Title 17 of California Code of Regulations Section 2502(f) (2), the County Health Officer has the discretion to release any data that is necessary to prevent the spread/occurrence of COVID-19. Given the high levels of outbreaks at the SNFs and jails and the highly transient nature of occupants and staff at homeless shelters, disclosing those numbers are necessary to prevent the spread/occurrence of COVID-19. Should other congregate facilities meet those threshold, the County Health Officer will evaluate to determine release of aggregate data for those facilities.

Testing Data

What tests are included in the testing data?

Only polymerase chain reaction (PCR) tests (diagnostic tests) are included in testing data.

What’s the difference between the daily testing data and cumulative data?

Daily testing data refers to new tests received by the HCA in CalREDIE on a given day and then reported publicly the following day. The daily counts include tests with various specimen collection dates so are not reflective of a particular day. Cumulative testing data refers to total test reports received by the HCA to date.

What is a Testing Positivity Rate? How is that rate calculated?

The Testing Positivity Rate is the percentage of total number of reported tests that resulted in a positive test. For our Testing Positivity Rate, we are using CDPH’s method of the total number of positive PCR tests divided by the total number of PCR tests conducted. This number is then multiplied by 100 to get a percentage.

Why is the Testing Positivity Rate important to monitoring COVID-19?

Testing Positivity Rate is important for monitoring elevated disease transmission in the county. The higher the number, the more the county is impacted by COVID-19.

Why is the State using a 7-day lag to measure Testing Positivity Rates?

CDPH uses a 7-day lag to base the calculation on more complete and reliable data. The 7-day lag allows for the State to “clean” and process the data due to reporting delays, which helps increase the level of accuracy.

Why do the testing numbers fluctuate so much even after they’ve been posted?

Labs can report tests to CDPH at any time after the test is resulted via the Electronic Laboratory Reporting (ELR) system. Depending on the lab’s capabilities and operations, tests performed and resulted on the same day could be reported on the same day or could be reported days later. Daily, HCA downloads the ELR system Orange County testing data. Once that is done, each test is then appropriately allocated to the date of specimen collection. This is what leads to the fluctuations in numbers.

Over time, the data becomes more and more accurate with the most recent days least complete and data from prior weeks or months more complete and accurate.

Can more than one test be attributed to the same person?

Yes, more than one test may be attributed to the same person. Some people in high-risk occupations or settings, such as health care workers or skilled nursing facility residents may need to be tested on multiple occasions due to ongoing elevated risk of infections. Each of these tests represents potential risk of infection, therefore it is important to capture all tests.

Case Data

Why do the case counts fluctuate?

Case counts fluctuate based on disease transmission and testing practices. Additionally, as Orange County and other local health jurisdictions complete their public health investigations, accurate determination of city of residence may result in cases transferred to the correct local health jurisdiction.

Is the case count number duplicated?

No, the case count is unduplicated. A person can only be counted once. Every time an individual tests positive is matched to that individual’s record so that they are only counted once.

Are out-of-county cases that are transferred to Orange County’s hospital system included in the total case count?

Case counts are based on the case’s residence. COVID-19 positive patients transferred from other counties will be included in the hospitalization count but not the case count.

Do out-of-county cases impact Orange County’s hospital metrics according to the State? 

The out-of-county COVID-19 hospitalized patients are included in the State metric but are not held negatively against the County.

What is the case rate and how is it calculated? 

The case rate is a way to account for the population size in order to make better comparisons between different areas with differing populations. The case rate is the number of cases in an area (like Orange County), divided by the population of that same area. It is often expressed in this site as per 100,000 population.

Why is the case rate important to monitoring the COVID-19 situation? 

Rates are an important way to compare our progress with COVID-19 with other areas. Case counts alone are not as meaningful, as places with large populations will usually have larger case counts, and smaller places will have smaller case counts.

For example, Orange County, with over 3 million residents, has a case count over 10,000 and Kings County has approximately 150,000 residents and less than 1,000 COVID-19 cases. When comparing rates, however, Orange County’s is much lower than Kings’.

Does the case rate change if people recover? 

No, the case rate represents confirmed cases over a specified population. It will not change based on patient outcome.

How do you calculate the number recovered? 

While every case of the new coronavirus that causes COVID-19 is reported to the HCA, there is no practical way to find out if they’ve recovered. Moreover, many people have experienced some symptoms of COVID-19, but were not tested, making it impossible to know the exact number of COVID-19 infections and recovered. However, because it is important to know approximately how many residents may have been exposed and recovered in Orange County, an attempt to estimate the number of recovered cases has been made by taking the difference between the prior 28-day cumulative case count and current day mortality to determine the current day recovered total. Please note that these data are only an estimate, and should be interpreted with caution.

Methodology: Prior 28-day cumulative case count - current day mortality = current day recovered.

For City-specific data, how many cases must a city or unincorporated area have before it is posted? 

For cities or unincorporated areas with less than 25,000 population, 5 or more cases are required before case counts will be reported.

For City-specific data, what is the reason for why the number may fluctuate? 

The data is preliminary and subject to change. As cases are investigated, the data is updated as additional information becomes available and corrections made, if appropriate. For example, a resident of Norwalk may have been tested in San Juan Capistrano. As the data is cleaned over time, that discovery will be made and the test result will be routed appropriately to Norwalk.

Hospitalization Data

Is the Orange County hospitals’ surge planning based on 33 hospitals or 26 hospitals?

Surge planning is based on 33 hospitals.

What is the hospitalization rate and is it important for monitoring COVID-19?

The hospitalization rate is the percent change in confirmed COVID-19 patients hospitalized: Calculated by comparing the average number of laboratory confirmed COVID-19 patients hospitalized over the past 3 days to the 3 days prior. The hospitalization rate is the number of residents admitted during a specified time period (usually a calendar year) divided by the population, and expressed as per 10,000 persons (per capita) proportion. The importance of monitoring the rate is that it provides objective details of patients with infection that is severe enough to warrant hospitalization. These details include but are not limited to demographics, co-morbidities, severity of illness. An example calculation for 1,000 persons hospitalized in Orange County: 1,000/3.2 million population X 10,000 = 3.13 per 10,000 population.

Why were these the metrics the State chose for monitoring COVID-19?

These metrics were chosen by CDPH to provide some early indication of developing areas of concern at the county-level. 14-day case rate and 7-day testing positivity are used to indicate elevated disease transmission. Percent change in confirmed COVID-19 patients hospitalized is used to monitor increasing hospitalizations. ICU bed and ventilator availability are used to determine hospital capacity. Elevated disease transmission and increasing hospitalization assesses the burden of COVID-19 in the county. Monitoring hospital capacity is important to determine if there is sufficient capacity remaining in the health care system to care for patients in the county.

Why do our numbers differ from the State?

The new dashboard will primarily rely on data directly from the State; but in some cases, such as ZIP code level maps of cases and deaths, we will rely on locally analyzed data.

How often is the HCA’s dashboard updated?

The dashboard will be updated daily, by the close of business (5 p.m.) each day.