As many as 646,000 people may die from influenza each year worldwide, according to the latest estimates from the Centers for Disease Control and Prevention — a larger number than what other health experts have predicted in years past.

The CDC said between 291,000 and 646,000 people die from seasonal flu-linked respiratory illnesses. Earlier projections from the World Health Organization’s earlier projections of deaths from seasonal flu — 250,000 to 500,000 per year — “are outdated,” according to the study published Wednesday in The Lancet.

This “builds the evidence base for influenza vaccination programs in other countries.”

“This work adds to a growing global understanding of the burden of influenza and populations at highest risk,” said Danielle Iuliano, a CDC researcher and the study’s lead author. “It builds the evidence base for influenza vaccination programs in other countries.”

Researchers at the CDC analyzed the WHO’s Global Health Estimate data from 1999 to 2015, including statistics from 33 countries that represent more than half of global population. They then used computer modeling to develop estimates for flu-linked deaths, excluding pandemics, in 185 countries.

Based on these new estimates, adults over age 75 and people living in parts of sub-Saharan Africa are most at-risk of dying from the flu, the study said, and people living in the Eastern Mediterranean and Southeast Asia also face a high risk.

“Estimates of influenza-associated mortality are important for national and international decision making on public health priorities,” the report said.

William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center in Nashville, said these revised estimates could prompt greater adoption of better methods of diagnosing and tracking flu strains around the world.

“The earlier we notice strains of influenza, the better we can combat them,” he said.