U.S. Coronavirus Data: Frequently Asked Questions

What is the source of this data?

Since late January 2020, The Times has tracked coronavirus cases and deaths as they are announced using data released by countries, states and local health officials. Times staff work around the clock to create, verify and maintain this data.

This data is used in Times reporting and graphics, sometimes as cumulative figures, new daily totals or per capita counts.

The Times uses testing and hospitalization data published by the U.S. Department of Health and Human Services, and has used data collected by The COVID Tracking Project. The Times uses case and death data for most countries from Johns Hopkins University.

How often are the virus tracking pages updated?

The Times’s virus tracking pages are updated multiple times a day, and county-level risk is updated every morning. Most states update their data daily, though some report less frequently. Many counties only update on weekdays.

Rhode Island, for example, doesn’t typically report on weekends, and this trend is visible as white gaps in the daily charts below. Counts on Mondays or Tuesdays may include totals from the weekend.

Local governments may also revise reported numbers as they get new information, and may offer updated data in press releases or on social media.

Testing and hospitalization data for the previous day is typically updated every afternoon.

Why do numbers and risk levels differ from what I’m seeing from my state or county government?

The Times data is sourced from states, counties and regional health departments. Local officials often report earlier than the states do, so this can be a source of variation. Displayed risk levels are based on an analysis of coronavirus case and testing data by The New York Times and public health experts, which may not align with states’ own risk assessments.

Jurisdictions typically count cases and deaths based on a person’s residence, rather than the location where they tested positive or died, though there are exceptions to this in Alaska, Hawaii and Vermont.

The Times also makes some adjustments to create a more uniform dataset across jurisdictions. For example, some states do not include cases in correctional institutions in county totals, and The Times includes these cases in the appropriate county when possible.

In some specific situations, such as an outbreak on a cruise ship or military vessel, The Times has tracked cases based on the locations where patients were treated.

There is also variation in the way states and counties report probable cases and deaths, which is described below.

Why is my county at a particular risk level?

The Times developed risk level guidance with public health experts at Johns Hopkins Bloomberg School of Public Health and Resolve to Save Lives, an initiative of Vital Strategies. The risk levels are determined for each location based on recent data about cases and testing. This is an independent analysis unrelated to states’ own risk level assessments.

Some locations are assigned an unknown risk level if there is insufficient data available. To view a detailed explanation of the thresholds for each risk level, view the “About the risk levels” section on risk pages.

What are probable cases and deaths, and are they included in the data?

While confirmed cases and deaths are counts of individuals whose coronavirus infections were confirmed by a molecular laboratory test, probable cases and deaths count individuals who meet criteria set by state and federal governments, including verified exposure to the virus, symptoms common to it, and other testing that suggested the virus.

Confirmed cases and deaths are widely considered to be an undercount of the virus’s impact, so many states and counties began reporting probable coronavirus cases after the Centers for Disease Control and Prevention issued guidance to do so in April and again in August.

Not all governments report these the same way: Some release only confirmed cases and deaths, some report confirmed and probable numbers separately, and others report a combined confirmed and probable figure. If a jurisdiction reports probable cases and deaths, these are typically presented on the health department website, though sometimes these are not clearly labeled. The Times verifies this information with officials and includes probable cases and deaths when reported, as recommended by the C.D.C.

To see whether a state includes probable cases and deaths, visit the individual state pages listed at the bottom of this page.

Why doesn’t the page show how many people have recovered?

Data on the number of recovered patients or currently active cases are not consistently available at the county level. The number of people who have recovered, as tracked by some states and counties, is an estimate based on an assumption that people diagnosed with Covid-19 have recovered after a particular length of time if they have not died. The criteria varies by state. Health officials do not typically follow up with people to find out when they recover.

Why do spikes sometimes appear in the daily case and death charts?

The Times data is based on the date cases and deaths are announced, as this is the closest to real-time data that is available from states. Governments sometimes revise data or report a single-day large increase in cases or deaths without specifying when those cases and deaths occurred, which can cause an irregular pattern in the daily reported figures. The Times is excluding these anomalies from seven-day averages when possible.

For example, the Times has noted a few anomalies in the U.S. daily deaths data, which are detailed here.

To see a detailed list of all reporting anomalies, visit the individual state pages listed at the bottom of this page.

Why do cumulative counts sometimes decrease?

Health officials frequently remove or reassign cases and deaths after receiving new information, resulting in small decreases in total state and county tallies. Common reasons include removing duplications or cases and deaths that turn out to involve people who live in other jurisdictions. Occasionally, jurisdictions report larger decreases after changing case or death definitions, as Massachusetts did in September.

How do Covid-19 deaths compare to other causes of death?

The Times has examined government mortality data to determine the number of “excess deaths” that have occurred this year, and has compared those deaths to official coronavirus death counts. This U.S. page and international page are updated regularly as data is available.

Tracking the Coronavirus