The number of whooping-cough cases in Salt Lake County dropped for the first time in three years during August.

Health officials don't know if it marks a turnaround, but they're hoping, said Pamela Davenport, Salt Lake Valley Health Department spokeswoman.

"The exciting point is that it decreased lower than the three-year average," she said.

After years of consistently high and climbing monthly pertussis counts, August brought only 25 cases, compared to 33 last August. The three-year case average for the month is 29, Davenport said. And while a decrease of eight over last August might not seem like much, it's the first time there's been any decrease in years, she added.

The statewide pertussis rate is well above the national average. Utah County has also been plagued with increases, but more than half the cases statewide are in Salt Lake County.

Pertussis is a highly contagious bacteria nicknamed "whooping cough" for the distinctive whoop sound of the cough, which may persist for many weeks or even months. It's potentially deadly for infants, who along with small children are vulnerable to complications.

County health experts believe the decrease may be due in part to an awareness campaign about whooping cough they launched recently, and to the availability of a vaccine for adolescents and adults, since childhood immunizations wear off.

"They've been giving a lot of (the Tdap) vaccine to seventh-graders in the clinics," Davenport said.

Dr. Dagmar Vitek said the department is "excited" about the decrease, but won't know if it really means anything until they see if numbers climb again, now that more children are back in school. The close confines mean a single child with pertussis could easily spread the disease to others, she noted in a press release announcing the decrease.

"We'll keep our fingers crossed it's a trend," Davenport said.