Nearly three times as many whooping cough (search) cases have been reported in California this year compared to 2004, according to the state Department of Health Services.

The state tallied 1,276 cases and four infant deaths through August. For the same period in 2004, it logged 450 cases and two deaths.

The higher numbers may be due to improved testing and diagnosis, rather than a surge in actual cases, officials said.

"The general consensus is that the increased number of cases is due to better awareness and increased testing," said Celia Woodfill, a state health department epidemiologist. "When the health department finds one case, it keeps investigating. And once you find one case of pertussis, you find more."

Nationally, whooping cough cases rose sharply starting in the 1990s. The 25,827 cases reported last year were the highest total since 1959, but didn't come close to the 265,000 cases in 1934, which was the peak before vaccinations became routine.

Health officials attributed the increase largely to adults and teenagers contracting the illness after immunity from childhood vaccinations (search) wore off.

The disease causes severe coughing, accompanied by "whooping" gasps for air, that can last for months. It spreads through coughs and sneezes.

Health officials recommend that babies be vaccinated five times: at 2, 4 and 6 months, 1 year and 15 months. Booster shots for adolescents and adults also were recently approved.