Cases of COVID-19 are reported to the Tennessee Department of Health (TDH) by clinicians and laboratories across the state. Initially, public health has fairly limited information about each person that has tested positive, such as their name, date of birth, and address. Public health professionals contact every case of COVID-19 statewide to interview them and learn more about their illness, exposures and contacts.
The information that TDH receives from clinicians and laboratories is sometimes incomplete or occasionally incorrect. As we work to publish updated case counts and basic information on our website as quickly as possible, sometimes this information changes as it is updated, and correct information is learned during the investigation. This may mean that a case can move from one county to another once the patient’s county of residence is confirmed during their interview.
The number of active cases is based on the number of total cases minus the number of deaths and the number of inactive/recovered cases. Beginning September 3, TDH defines “inactive/recovered" as people who are (1) not deceased, and (2) at least 14 days beyond their symptom onset date, or are at least 14 days beyond the first test confirming their illness if asymptomatic.
Prior to September 3, TDH defined "recovered" as people who are not deceased and (1) have been confirmed to be asymptomatic by their local or regional health department and have completed their required isolation period or (2) are at least 21 days beyond their symptom onset date, or the first test confirming their illness if asymptomatic.
Pending refers to individuals who have been determined to be confirmed cases but the full public health investigation is still pending.
As a case investigation is conducted, more information is learned about the individual. Not all information may be gathered at one time, so different data points may be pending for each case.
If someone had COVID-19 when they died, they will be counted as a COVID-19 death. An exception to this is when a case died of something completely independent to COVID-19, like due to a car wreck.
- Anyone who does not have a Tennessee home of residence is counted as “Out of State”. These individuals sought care at a Tennessee facility and may be spending their infectious period in Tennessee.
- Cases among Tennessee residents are counted by their county of residence. Residents of other states who were tested at Tennessee healthcare facilities or laboratories are counted as “Out of TN.”
At a Tennessee healthcare facility or laboratory.
TDH routinely collects data about hospitalizations through case interview with people infected with COVID-19. This is how we monitor cumulative hospitalizations and is helpful to assess disease severity (how many COVID-19 patients require hospitalization), impact of vaccination status, demographics of hospitalized patients, etc. However, this is not reflective of real-time hospitalizations or healthcare system strain because it takes time to reach and interview cases, if they can be reached at all (see additional information below).
If TDH cannot reach someone for a case interview, then we may not know if they were hospitalized and therefore it would not have been reflected in the downloadable dataset prior to the completion of a new data linkage 8/31/21. TDH recently completed a process to link COVID-19 surveillance data to hospitalization data from the Tennessee Hospital Association. This has allowed us to have more comprehensive information on cumulative hospitalizations throughout the pandemic.
Please note, TDH presents two different data points about hospitalizations: current and total (cumulative) hospitalizations from COVID-19.On our main COVID-19 webpage, the hospitalization information in the green bar reflects patients currently hospitalized with COVID-19 across the state.
This is also presented in the ‘hospitalization data’ section. This is a marker of current hospitalizations and healthcare system strain from COVID-19. These data come from hospitals reporting information to TDH daily about the number of admitted COVID patients, available beds, staff, etc. This has not changed.
In addition, the hospitalization information in the daily data PDF, county dashboards and downloadable datasets, reflects all patients that have ever been hospitalized with COVID-19. This is not a marker of current hospitalizations or potential healthcare system strain from COVID-19, but more reflective of disease severity and the percent of patients that require hospitalization for their illness (currently ~4% of all COVID patients). This information is captured through case interview and reflects the county of residence of the COVID-19 patient, not necessarily where they were hospitalized. These data often lag substantially behind our ‘hospitalization data’ and underrepresent hospitalizations. The timeliness of the hospitalizations in this dataset will be improved with this new data linkage.
Hospitalization data reflect the cumulative (total) number of cases that were ever hospitalized from COVID-19. It does not reflect the number of people currently hospitalized.
We present two different data points about hospitalizations: current and total (cumulative) hospitalizations from COVID-19.
On our main COVID-19 webpage, the hospitalization information in the green bar reflects patients currently hospitalized with COVID-19 across the state. This is also presented in the ‘hospitalization data’ section. This is a marker of current hospitalizations and potential healthcare system strain from COVID-19. These data come from hospitals reporting information to TDH daily about the number of admitted COVID patients, available beds, staff, etc.
In addition, the hospitalization information in the daily data PDF, county dashboards and downloadable datasets, reflects all patients that have ever been hospitalized with COVID-19. This is not a marker of current hospitalizations or potential healthcare system strain from COVID-19, but more reflective of disease severity and the percent of patients that require hospitalization for their illness (currently ~4% of all COVID patients). This information is captured through case interview and reflects the county of residence of the COVID-19 patient, not necessarily where they were hospitalized. These data often lag substantially behind our ‘hospitalization data’ and underrepresent hospitalizations.
Laboratory reports of positive cases are reported to metro and local health departments as soon as results are available. State numbers are updated at 2 p.m. CDT daily. There may be a lag in the reporting of cumulative numbers at the state level. Metro Health Departments may also include individuals from out of Tennessee in their localized counts if the case is remaining in that county throughout the course of their illness.
Every laboratory has varying turnaround times. On average, if a specimen is tested at the State Public Health Lab, the results are ready within 48 hours of the time the specimen is received at the lab. Specimens collected by health departments may be sent to outside laboratories and turnaround times for these specimens may differ.
COVID-19 is a reportable condition in Tennessee. This means that clinicians and laboratories are required to report known cases to the Department of Health within 24 hours.
The Department of Health receives lab results (both positive and negative) from laboratories daily, and data from healthcare providers within 24 hours of identifying a case of COVID-19.
Beginning on Friday, June 12th, facilities who do not have any ongoing transmission of COVID-19 (no new cases among residents or staff in the preceding 28 days) will be removed from the website. Datasets with historic data will be available on the website.
These datasets are a running list of information reported out on the TN Department of Health website daily since Tennessee’s first case. If a variable was not on the website at a given time, there is no data to report for that timeframe.
A four day moving average is the average of one data point and the three preceding data points. Looking at a moving average helps to understand trends and account for fluctuations in the data.
- The Total Labs by Zip Codes and Total Cases by Zip Codes maps are updated once weekly on Fridays.
- The Incidence Rate and Testing Rate maps are updated once daily.
- An incidence rate looks at the number of cases of a disease divided by the population in that area. The incidence rate map shows:
- The number of COVID-19 cases in a given county since the outbreak started per 100,000 population. For example, if MadeUpCounty had an incidence rate of 3.0, this would mean there have been three cases of COVID-19 per 100,000 people that live in that county since the outbreak started. If MadeUpCounty’s population is 500,000, they would have approximately 15 cases.
- The population of the county is from the 2018 projected population estimate for Tennessee
- Why do we look at incidence rates?
- Incidence rates allow us to compare the burden of disease between counties with different population sizes.
- The testing rate is the total number of individuals tested for SARS-CoV-2 (the virus that causes COVID-19) in a county divided by the county population.
- The population of the county is from the 2018 projected population estimate for Tennessee.
Beginning Friday, June 12, 2020 the Tennessee Department of Health will provide more comprehensive information about the COVID-19 pandemic in Tennessee by updating data metrics presented on our COVID-19 webpage.
- The total number of COVID-19 cases presented beginning on 6/12 will include both confirmed and probable cases.
- On the full data report, the numbers will be broken down into confirmed and probable cases and confirmed and probable deaths consistent with Centers for Disease Control and Prevention surveillance case definitions: wwwn.cdc.gov/nndss/conditions/coronavirus-disease-2019-covid-19/case-definition/2020/.
- Our daily case count graph, demographics and outcomes reported include both confirmed and probable cases.
A confirmed case is someone who tested positive (via PCR test) for the virus that causes COVID-19 (SARS-CoV-2).
A probable case is someone who may have tested negative by PCR, tested positive by another type of test or may not have been tested at all, but has an illness consistent with COVID-19 and may have other risk factors. For example:
- If a person is a close contact of a COVID-19 case and has a clinically-compatible illness, this person meets the criteria to be a probable case.
- If a health care provider diagnoses a person with clinically-compatible illness with COVID-19, regardless of the test results, this person meets the probable case criteria.
- If a person dies and the health care provider that signs their death certificate determined that COVID-19 disease was their cause of death or a significant condition contributing to death, then the person meets the probable case criteria and would be considered a probable death.
For both confirmed and probable cases, public health officials take the same actions. All cases (confirmed and probable) undergo a case investigation and contact tracing interview and are asked to isolate per CDC/TDH guidance. Their contacts are then contacted and asked to quarantine for 14 days.
The number of cases shows the number of individual people who are either confirmed or probable COVID-19 cases. Individuals are only counted once in this number, no matter how many positive tests they might have had. The number of positive tests is the total number of PCR-positive laboratory results that have been reported to TDH. The number of negative tests is the total number of PCR-negative laboratory results that have been reported to TDH.
No, these numbers only show the testing volume for PCR tests, which look for active infection.