Feb. 1, 2013 -- The flu continues to wane on a nationwide basis, but don't tell that to residents of the western United States.
Of the 24 states reporting high levels of flu-like illness, 19 were west of the Mississippi River for the week ending Jan. 26, according to the latest "Flu View" report from the CDC.
In the last week of 2012, 18 of the 29 states reporting high flu-like activity levels lay east of the Mississippi.
This east-to-west migration of influenza is a long-standing pattern, according to the CDC.
Although the percentage of doctor visits for suspected flu was declining throughout most of the country, it was rising steeply in in eight Western states: Alaska, Arizona, California, Hawaii, Idaho, Nevada, Oregon, and Washington. In the Midwestern states of Iowa, Kansas, Missouri, and Nebraska, the flu-like illness crept up slightly.
Nationwide, the proportion of people going to the doctor for suspected flu was 4.2%, down slightly from the previous week. This rate has been decreasing since it reached 5.6% in the last week of 2012.
The number of states reporting widespread flu fell to 42.
The rate of hospitalizations per 100,000 people attributed to the flu and pneumonia kept climbing, however, reaching 25.9 for the flu season so far.
Both the hospitalization and death rates for the flu typically lag behind those for flu activity, because people infected with the virus may not become seriously ill right away, or promptly seek medical care.
Throughout the first three weeks of January, the percentage of deaths attributed to flu in 122 benchmark cities was on the rise, but this rate decreased slightly to 9.4% in week four, down from 9.8% but still far above the epidemic threshold of 7.2%