There is a connection between infections and brain health that has been quietly accumulating in the research literature for years — and that has come into much sharper focus since 2020, when millions of people began experiencing firsthand what it looks like when a viral infection affects the brain’s immune system in lasting ways.
Long COVID, with its characteristic brain fog, cognitive sluggishness, and difficulty concentrating, has brought the infection-brain connection into public consciousness in a way that previous research had not. But the phenomenon it represents — viral and bacterial infections triggering neuroinflammation that persists long after the acute infection has resolved — is not new. It has been observed across a range of pathogens, and the research suggests it may be more significant for long-term brain health than most of us have been told.
How Infections Affect the Brain
When the body encounters an infection, the immune system mounts a response — and that response, as we’ve explored throughout this series, extends to the brain. Microglial cells — the brain’s immune system — activate in response to the systemic inflammatory signals generated by an infection, even when the infection itself is not directly in the brain.
For many acute infections, this microglial activation is temporary. The infection resolves, the immune response winds down, and the microglia return to their normal surveillance mode. But for some infections, in some individuals, the microglial activation persists. The immune system remains in a state of heightened alert even after the pathogen is gone — and that persistent neuroinflammation can affect cognitive function, mood, energy, and overall brain health in ways that outlast the infection by months or years.
The Viral Suspects
Several specific pathogens have received attention in the research for their potential links to long-term neurological effects.
Herpes simplex virus type 1 — the virus responsible for cold sores, present in the majority of the adult population — has been studied extensively for a potential association with Alzheimer’s disease risk. The hypothesis is that HSV-1, which can travel to the brain and remain latent there, may be reactivated under conditions of immune stress and contribute to the inflammatory processes associated with cognitive decline. The evidence is not definitive, but it is suggestive enough to be taken seriously in the research community.
Epstein-Barr virus, which causes mononucleosis, has been associated with increased risk of multiple neurological conditions. SARS-CoV-2, the virus responsible for COVID-19, has demonstrated the capacity to trigger neuroinflammation and cognitive effects in a subset of individuals that persist long after acute infection. And influenza, in older adults, has been linked to increased short-term cognitive vulnerability.
What This Means for Those Who Have Been Ill
I want to speak directly to those who may be reading this in the wake of a significant illness — whether that is long COVID, a serious infection of another kind, or a pattern of recurrent infections — and experiencing cognitive effects they weren’t expecting.
What you are experiencing has a mechanism. It is not imaginary, not a sign of weakness, and not inevitable to be permanent. Neuroinflammation triggered by infection is real, measurable, and — in many cases — responsive to the same interventions that support brain immune health in general: anti-inflammatory diet, sleep, stress reduction, movement, and support for gut health.
This does not mean recovery is simple or quick. It means there is a biological basis for your experience and a rationale for the interventions most likely to help.
Prevention as Brain Protection
From a brain health perspective, preventing infections — particularly the ones with the strongest evidence for neurological effects — is a meaningful act of cognitive self-care.
Maintaining the lifestyle foundations that support a robust immune system — adequate sleep, anti-inflammatory diet, stress management, regular movement — reduces both the frequency and the severity of infections.
And supporting the gut microbiome, which plays a central role in immune regulation, is relevant here as it is across virtually every dimension of brain health we’ve explored in this series.
A Gentle Closing
The relationship between infections and brain health is one of the most active areas of current research — and one of the most hopeful, because understanding the mechanism opens doors to intervention.
The infections you have had are part of your history. What you do to support your brain’s immune system going forward is part of your future. Both matter.
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