Influenza and Parkinson’s: How Big Is the Risk? An Updated Meta-Analysis

Making sense of the complicated epidemiological link between influenza and Parkinson’s disease.

Image adapted from rawpixel.com.

Originally published at The Infected Neuron on February 28, 2025.

Everyone knows the U.S. is experiencing one of the worst flu seasons in 15 years. From October 2024 to February 2025, about 50 million people were infected, almost a million were hospitalized, and almost 100,000 died (Figure 1). Certain regions in Europe and Asia are also experiencing one of the most aggressive flu seasons this year. Japan, in particular, recorded its worst flu season since it started keeping records 25 years ago in 1999.

These recent flu outbreaks are primarily driven by the avian influenza A virus (IAV). This strain circulates among wild birds and poultry, which can spread to humans. Unlike the influenza B virus (IBV), which is generally milder and mainly infects humans, the pandemic risk of IAV is high due to its ability to reassort with animal influenza strains, leading to new, unpredictable strains. While both IAV and IBV can drive seasonal flu, IAV is often more serious. So, I’m mainly referring to IAV in this article.