The need for the CDC to communicate clearly and transparently about rapidly evolving science is underscored by a quiet change in how the agency reports Covid death details.

The past two years have created numerous communication challenges for the agency, which works with massive amounts of data from scores of different sources.

Humans are fallible, but there should always be an effort to explain what happened and what is being done to prevent it from happening again.

He said that you have to over-communicate if something needs to be corrected.

Last week, after reporting from the Guardian on mortality rates among children, the CDC corrected a coding logic error that had inadvertently added more than 72,000 Covid deaths of all ages to the data tracker.

The agency briefly noted the change in a footnote, but did not explain how the error occurred or how long it had been in effect.

A total of 72,279 deaths in all age groups reported across 26 states were removed from the tracker because the CDC accidentally counted deaths that were not related to Covid-19.

According to a source familiar with the issue, the CDC asks two questions when they report deaths.

One data field asks if a person died from illness/complications of illness, and the other asks for the date of death. The date of death should be provided when the answer is yes.

There was a problem if the date of death was included in the answer. If a date was provided, the CDC's system assumed that the answer was an error and switched it to.

This resulted in an overcount of deaths due to Covid, and the error was corrected last week. The coding error was in effect for a while, but the CDC didn't say how long it was in effect.

A general view of the US Centers for Disease Control and Prevention (CDC) headquarters in Atlanta, Georgia.

A general view of the US Centers for Disease Control and Prevention (CDC) headquarters in Atlanta, Georgia. Photograph: Tami Chappell/Reuters

Working with near real-time data in an emergency is critical to guide decision-making, but may also mean we have incomplete information when it is first reported.

The death counts in the data tracker are real-time and subject to change, while the National Center for Health Statistics is the most complete source of data.

It is difficult to report causes of death in non-pandemic times.

Glen Nowak is a former director of media relations at the CDC and co-director of the Center for Health and Risk Communication at the University of Georgia.

There are a number of reasons for that. The initial data is usually reported by healthcare providers. Death certificates take time to complete and the cause of death may be difficult to determine. One-third of deaths are reported after 10 days, and states may have lags in sending the data to the CDC. The data can be involved in the CDC's process.

The quality of CDC data can vary widely because of the under-investment in public health at the national, state, city and local levels.

The public health and healthcare system makes it difficult to collect data.

The CDC estimates that more than 968,000 Americans have died of Covid, and this change doesn't seem to have changed that. There may be more than 180,000 deaths that aren't counted because of the demographic data on the tracker.

The recent change to demographic data shows the difficulty of offering up-to-date assessments while data reporting and analysis have lag in the face of a massive outbreak. Data on the same topic can be different depending on how numbers are calculated.

The level of precision that you see in these numbers makes you think that they must be really accurate. They are aware of the scope of Covid compared to other illnesses.

I don't think public health and others do a good enough job of reminding people that the numbers have significant margins of error.

Changes are inevitable and frequent as the scientific evidence accumulates. Significant changes in calculations and records need to be explained clearly, particularly in an emergency where the public is frequently aware of data.

The best practice is to have daily briefings so that you can keep up with what's happening. The agency dealt with past swine flu and other diseases.

He said that the briefings should be held by scientists with expertise in many areas. The current CDC administration has been getting back in the habit of doing that, and I hope that continues.

The CDC provides data to inform national policy, and public health policies often have some political component, according to Frieden. You should never have concerns about the accuracy of the data.