DENVER (AP) — An annual aerial survey of forest health in Colorado shows the mountain pine beetle epidemic is slowing dramatically, but the spruce beetle outbreak is expanding, forest officials said Wednesday.

The mountain pine beetle epidemic has spread by 31,000 acres, down from an increase of 140,000 acres reported last year, the U.S. Forest Service and Colorado State Forest Service said. Since the first signs of the outbreak in 1996, the infestation has grown to nearly 3.4 million acres, or roughly 5,300 square miles. The infestation remains active from Estes Park to Leadville.