A multinational study that analyzed data from 47 countries over 15 years shows a worldwide increase in annual deaths caused by seasonal influenza-related respiratory illnesses. Published in The Lancet, the study was conducted by the Centers for Disease Control and Prevention and global partners in collaboration with Emory's Rollins School of Public Health. 

A. Danielle Iuliano, PhD, adjunct professor at Rollins, is lead author of the paper and the paper. Howard Chang, PhD, associate professor at Rollins, is lead statistician.

The researchers report that between 291,000 and 646,000 people worldwide die from seasonal flu-related illnesses annually. Previous estimates placed this number at 250,000 to 500,000. The estimate excludes deaths during pandemics.  

"This work adds to a growing global understanding of the burden of influenza and populations at highest risk," says Iuliano. "It builds the evidence base for influenza vaccination programs in other countries."

The new estimates were calculated using death records and seasonal influenza surveillance information from 47 countries from the years 1999-2015. Researchers calculated region-specific estimates and age-specific mortality estimates for people younger than 65, people 65-74, and people 75 and older. They found that the greatest flu mortality burden was seen in the world's poorest regions and among older adults. People age 75 and older and people living in sub-Saharan African countries experienced the highest rates of flu-associated respiratory deaths. Eastern Mediterranean and Southeast Asian countries had slightly lower but still high rates of flu-associated respiratory deaths.

Despite World Health Organization recommendations to use flu vaccination to help protect people in high-risk populations, few developing countries have seasonal flu vaccination programs or the capacity to produce and distribute seasonal or pandemic vaccines.