An intensifying flu season could have ramifications for managed-care companies with major operations in harder-hit regions, especially Texas, depending on how well the activity compares with company expectations.

That is the view of Stifel Nicolaus analyst Thomas Carroll, who said data derived from Google Flu Trends indicates that influenza-related doctor visits, while lower than last year at this time, have doubled in the last three weeks nationally. In Texas, flu-related activity has reached 8.3%, he said, compared with 4.6% last year.

Such activity could affect results for four managed-care companies focused on flu-sensitive Medicaid or Medicare populations that do big business in the Lone Star State - Centene Corp. (CNC), Healthspring Inc. (HS), Amerigroup Corp. (AGP) and Universal American Corp. (UAM) - Carroll said in an interview Wednesday. He also published a report on the latest data.

"Those are the ones that I think the flu could have the most impact on," Carroll said. He had a caveat: If flu prevalence is higher than company expectations it could be an issue. If a company has anticipated an intense flu season and reserved accordingly, it won't be.

"There's a potential for either negative sentiment to build going into first quarter [reporting season] or for the actual impact of flu to have a negative effect" on medical expenses for those companies, he said.

Texas is the largest market for Medicaid managed-care company Centene, which derives 33% of its revenue from that state, Carroll said. Healthspring, a Medicare health insurer, generates some 30% of its revenue from Texas, he said. The numbers are 29% for Medicaid managed-care concern Amerigroup and 23% for Medicare player Universal American from Texas, he said.

Humana Inc. (HUM) has exposure in Texas and other states where higher numbers of flu cases are indicated, although the company is larger and more diversified, Carroll noted.

This is the first year that data from Google Flu Trends is available, and it is tracking closely to data from the U.S. Centers for Disease Control and Prevention, which lags the Google data, he said.

Google Flu Trends provides estimates of flu activity in the U.S. based on aggregated queries in the Google Inc. (GOOG) search engine. Google says that by comparing its counts of search queries with CDC data, it has found a close relationship between how many people search for flu-related topics and how many have flu symptoms.

Representatives of Centene, Healthspring and Universal American didn't immediately return calls or weren't available for comment. A Humana spokesman said the company isn't seeing any significant effect from the flu this year. An Amerigroup spokesman said the company doesn't discuss the flu until after the first quarter. Amerigroup has 452,000 members in Medicaid and other publicly funded health programs in Texas.

-By Dinah Wisenberg Brin, Dow Jones Newswires; 215-656-8285; dinah.brin@dowjones.com