The uptick in influenza-like illnesses (ILI) that experts working with AccuWeather predicted did indeed occur. Most of the states in the United States - in a reversal of the last couple of weeks - experienced an increase in activity, according to the most recent data. However, its impact does not figure to be long-lasting for most of those states, those same experts predict.
Visits to health care providers for ILI increased from 4.7 percent last week to 5.0% this week, a slight increase after two straight weeks of declining totals, according to the latest report from the Centers for Disease Control and Prevention (CDC). Flu activity remains high nationally, the CDC notes; researchers at the Biocomplexity Institute, who work in a research partnership with AccuWeather, see the increase as the sum of its parts.
"It's a tough balance to strike since the picture at the national level is really a combination of a lot of smaller stories playing out in the different states," Dr. Bryan Lewis, a professor at the Biocomplexity Institute at the University of Virginia, told AccuWeather.
Some 38 states experienced an increase in activity; however, many of these increases were modest and many states continued to decline, the Biocomplexity researchers note. A total of 15 states had ILI activity that was considered either "moderate," "low," or "minimal," according to the CDC.
"In general, the current forecasts aren't calling for this ‘blip' to continue significantly and cause a larger national second peak," Lewis told AccuWeather. "But my gut says there are several states - and they are scattered all over the place - that could have a reasonable resurgence in the coming weeks, meaning a second peak with a couple of weeks of increasing infection, namely Missouri, Ohio, Alabama, Idaho and New England-area states."
The CDC estimates that so far this season there have been at least 15 million flu illnesses, 140,000 hospitalizations and 8,200 deaths from the flu. It's the tenth straight week flu activity is above baseline normal (2.4 percent). Last year, levels of ILI in the U.S. were at or above baseline for 21 straight weeks.
Influenza A continues to increase its share of activity nationally and is increasing its overall prevalence in nearly all regions, according to the Biocomplexity Institute researchers. Influenza B causes significant illness in those stricken; however, hospitalization and death are less frequent than with Influenza A.
Flu season typically begins in October, peaks between December and February and lasts well into March although activity can last as late as May. Flu viruses are more stable in cold air and the low humidity allows the virus particles to remain in the air, according to Peter Palese, who was the lead author on a key flu study in 2007. For example, there is no real flu season in the tropics.