With flu season still in full force, the Daily Beast has taken stock and ranked the nation's sickest cities. Houston makes the Top 20, but relatively low at No. 18. Many of the bedridden burgs are our Sun Belt neighbors, including Tampa (No. 2), Mobile (No. 3), San Diego (No. 4), Jacksonville (No. 5) and Phoenix (No. 15).

The Lone Star State, which claims a 70.1 percent influenza vaccination coverage, unfortunately scored relatively high overall, with San Antonio ranking at No. 8 and Dallas winning slot 14. Houston claimed its title just above the Big Apple, where 14 out of every 100,000 die of flu and pneumonia each year (the number is 16 per 100,000 in the Bayou City).

Why the emphasis on the dirty South?

"We don't know why," Glenna Rohlfing, director of clinical operations for SDI Health, an analytics firm, told the Daily Beast. "Some will say it's because Southern schools go back to school earlier, they start earlier than the Northeast schools, everybody has their speculation."

The Beast culled its rankings from SDI Health Ranking, statewide vaccination coverage, influenza and pneumonia deaths per 100,000 people and estimated flu activity for the remainder of the flu season.

Despite the broad range of factors, the data is still a little iffy. For example, Mobile's flu activity was estimated based on average changes in flu activity from regional cities Atlanta, Miami, Orlando, Tampa and Jacksonville.

The No. 1 sickest city? Dayton, Ohio.