Three more people have died of the flu in Dallas County, bringing the total number of deaths to nine this season, officials announced Thursday.

All three patients were Dallas residents, ages 37, 69 and 78. The ages of the previous patients were 98, 59, 81, 73, 80 and 60.

"Older adults, individuals with chronic health conditions, pregnant women, young children and infants are more vulnerable to flu illness," Dr. Christopher Perkins, Dallas County health authority, said in a statement. "With influenza activity on the rise, individuals in these groups should take special precaution as we continue throughout the season."

Texas is among 36 states to have reported widespread flu activity this season, according to the Centers for Disease Control.

The CDC recommends a yearly flu vaccine for everyone six months and older.

About 20 percent of influenza tests in Dallas County hospitals came back positive before Dec. 23, Dallas County Health and Human Services said in a recent report, which is 5.5 percent higher than the national average.

Flu season typically peaks in January and February. Symptoms include a fever, cough or sore throat, aches, chills, and fatigue.