According to the CDC's map of flu activity, 46 states are currently reporting widespread H1N1 flu cases. Since almost all states have by now reported outbreaks, this map, which only a month ago was dappled with the different colors of flu levels, is now almost uniformly brown.
The CDC notes on its site that the map only shows geographical trends and "does not measure the severity of influenza activity." But with the CDC reporting little variance between states, let alone within each state, it is easy to conclude that the amount of swine flu activity is the same across the country.
A check of 60 hospitals by ABC News suggests a very different picture. The collection of reports from these hospitals, though not a scientific sample, suggested that not only does the extent and severity of the illness vary from region to region, but in some cases it varies even among hospitals in the same state.
In order to get a better idea of how flu activity varies across the nation, we asked hospitals to rate their level of flu activity in their emergency department and report the number of H1N1 patients in their intensive care unit (ICU) -- a sign that at least some cases were severe enough to warrant extraordinary treatment measures.
At least 10 out of the 60 hospitals reported heavy activity of H1N1 in their emergency departments, but nearly twice as many said flu levels were "moderate" and the largest proportion, 21 hospitals, said that the situation was "light" in their ER and reported few, if any, patients in the ICU due to swine flu-related problems.
There is no doubt that there are areas where flu activity is high. The Midwest remained the heaviest area of activity, and other "heavy" hospitals were spread out across the country.
In Columbus, Ohio, both the Nationwide Children's Hospital and Ohio State University Medical Center, have several patients who are currently on lung and heart support machines. They both reported heavy levels.
Richard Davis, associate executive director of Ohio State University Hospital and the Ross Heart Hospital, also in Columbus, said that out of a total of 38 medical ICU beds, there were only three that were unfilled.
"That's a pretty fine margin, frankly," Davis said. "We, like others, have a very thin excess when it comes down to ICU capacity."
In the South, there were signs that the strong activity was declining in some areas but not others. In the past month, such areas as Austin, Texas, attracted national attention when Dell's Children's Medical Center in Austin set up a tent outside the emergency department to accommodate all the people arriving with flu-like symptoms. But today several hospitals in Texas including the Harris County Hospital District reported light activity.
Though the southern states were among the first to receive the CDC's brown label, indicating "widespread" activity, flu levels seem to be easing up a bit with Emory University, in Atlanta, Ga., and Baptist Hospital Northeast in La Grange, Ky., reporting light activity.
However, there are still areas of the south where flu activity seems strong. In Florida, flu levels were still reported as heavy.
A spokesperson for the Hillsborough County emergency department in Tampa, Fla., said influenza-like illnesses are "well above what we normally see at this time of year," and Florida Hospital in Orlando, reported 4 patients in the ICU for H1N1-related complications.
In the Northeast, levels of flu have typically been lower than other regions, but several areas reported an uptick in swine flu, predominantly in the southern portion of the region. In Pennsylvania, Lancaster General Hospital had moderate to heavy levels, as did University of Pittsburgh Hospital. In New Jersey, Cooper Health in Camden reported moderate flu activity, though no ICU patients.
Many other medical centers in the Northeast remain relatively unscathed, with three Boston hospitals reporting light activity and several in the New York area, such as Beth Israel Medical Center, St. Luke's Roosevelt Hospital, St. Vincent Medical Center, and Staten Island University, also reporting light to very light flu levels.
Out West, the strong activity previously noted in some areas of California has seemingly migrated east to Denver and north to Oregon. Levels were moderate at the Oregon Health and Sciences University Hospital, and two hospitals in Denver, Colo. -- Porter Adventist and University of Colorado Denver Hospital -- now report heavy activity and swine flu patients in the ICU.
California, which has gotten a lot of attention for high levels of swine flu, was a prime example of how flu activity can vary greatly within a state and even within regions of a state. Of the seven California hospitals who responded to the ABC News query, two reported light flu activity, two heavy, and three moderate.
Dr. Larry Satkowiak, medical director of the emergency department at Children's Hospital Central California near Fresno, said that at his hospital, the virus has certainly added to the normal emergency department caseload.
"We're up about 25 percent from last October," he said. "Most of that is due to flu-related illnesses."
Roughly 300 miles south, Dr. Jake Jacoby, hospital director for emergency preparedness and response at the University of California at San Diego, said they "have not activated any surge steps at this point," he said.
"We are ready to deal with larger numbers of patients, but so far, we have not had to worry about that."
Even within the same city, levels can vary. At Georgetown University Hospital in Washington, D.C., levels are light, but across town at Providence Hospital, flu activity is at a "very heavy volume" according to Stephanie Herztog, director of public relations. At George Washington University's medical center, activity is somewhere in the middle.
Though these 20-odd "light" responders hint that there may be some areas less "widespread" than the CDC map would imply, there certainly are many hospitals nationwide struggling with heavy activity and widespread increases in ER volume.
Dr. Dennis Cunningham, medical director of the epidemiology department at Nationwide Children's Hospital, is currently seeing a bump in emergency department visits, but he notes that "when you talk to infectious disease experts, what they will always say is that the only thing that is predictable about influenza is that it's unpredictable."
"I've been doing this for 21 years, and there's just no way to predict what will happen with influenza," Satkowiak agreed. "We have no idea what the seasonal flu is going to do."