ATLANTA – U.S. life expectancy has hit another all-time high, rising above 78 years. The estimate of 78 years and 2 months is for a baby born in 2009, and comes from a preliminary report released Wednesday by the Centers for Disease Control and Prevention.

About 2.4 million people died in the United States in 2009 — roughly 36,000 fewer deaths than the year before.

Deaths were down for a range of causes, from heart disease to homicide, so experts don’t believe there’s one simple explanation for the increase in life expectancy. Better medical treatment, vaccination campaigns and public health measures against smoking are believed to be having an impact.

U.S. life expectancy has been generally increasing since at least the 1940s, though some years it held steady and a few times it temporarily dipped.

Previously, the CDC said a one-month dip occurred in 2008 to 77 years and 11 months. But in Wednesday’s report, the agency corrected that to 78 years, attributing the glitch to a computer programming error.

The 2009 report by the CDC’s National Center for Health Statistics is based on nearly all the death certificates for that year. A final report is due later this year.

More good news from the new report: The infant mortality rate hit a record low of 6.42 deaths per 1,000 live births, a drop of nearly 3 percent from 2008.

But not everyone benefited. While life expectancy for whites rose, it held steady for blacks.

As a result, the racial gap got a little wider. Whites already live about four years longer than blacks, and the margin grew by about two months.

The gap between the sexes also persisted. Overall male life expectancy is roughly 75 1/2, for females it’s about 80 1/2.

Other highlights:

Death rates declined slightly for 10 of the 15 leading causes of death, including heart disease, cancer, stroke, accidents, Alzheimer’s disease, homicide and influenza and pneumonia.

Suicide passed blood infections to become the 10th leading cause of death.

The influenza/pneumonia death rate dropped nearly 5 percent, even though 2009 was the year that the swine flu pandemic hit.