We recently came across this USA Today H1N1 Flu Map and it immediately raised a few red flags for us. At first glance, the map appears to offer the exact number of H1N1 cases by region. Here’s the problem: no one is actually counting individual cases of H1N1 at this stage of the pandemic and there is no indication on the USA Today map that their numbers represent estimates. Additionally, the count of H1N1 cases listed (sourced to the CDC) bears little resemblance to recent estimates from the CDC.
We raise the issue not to highlight the mistakes of the USA Today map, but to encourage caution and diligence when reporting the number and location of swine flu cases. There is an understandable inclination to provide specific numbers and geographic data to your audience. It’s frustrating that there are no official hard numbers to report. The danger lies in what fills that vacuum.
A number of popular flu maps, such as FluTracker, Google Flu Trends, and Health Map, (which feeds data to the Harvard Med School iPhone app we recently featured) rely on a mix of formal and informal sources to build out their source data. These informal sources can include self reporting, media reports, and even the frequency of flu-related keyword searches. Be careful using this kind of information as a replacement for official estimates. There is a high risk of bad data self-replicating among these platforms — and in your reports.
Since the end of August, the CDC has been providing estimates of H1N1 cases based on routine surveillance methods and statistical samples of hospitalizations and deaths for flu-like symptoms. Last week, the CDC released its new methodology for tracking the spread of H1N1. The count remains based on estimates, but the CDC feels it is a more accurate picture of the current situation. They are providing general estimates along with more specific numbers (pdf) that allow you to see how they extrapolate estimates from their surveillance methods.
So take a moment to check the official CDC estimates before running with a number published elsewhere. And if you have any questions or need additional information about official estimates, contact the CDC press office for clarification.