As a physician who has spent decades investigating the root causes of chronic illness, I'm continually amazed by how interconnected our health truly is. Today, I want to share something that may fundamentally shift how you think about Alzheimer's disease and dementia—groundbreaking research revealing that these devastating conditions may not be purely genetic or age-related, but potentially triggered by infections that have been quietly residing in our bodies for years.

The Paradigm Shift: From Plaques to Pathogens

For over a century, we've focused on amyloid plaques and tau tangles as the primary culprits in Alzheimer's disease. But what if these hallmark features aren't the cause, but rather the consequence of something deeper? Recent research published in multiple prestigious journals is revealing a fascinating possibility: What if amyloid-beta actually serves as an antimicrobial defense mechanism, and the plaques we see in Alzheimer's brains are the battlefield remnants of the immune system's fight against infectious invaders?

This isn't just theoretical speculation. The evidence linking infections to Alzheimer's disease has grown so compelling that it demands our attention—and our action.

The Mouth-Brain Connection: Periodontitis and Porphyromonas gingivalis

Let's start with something that affects nearly half of American adults over 30: gum disease. A groundbreaking 2025 study published in ScienceDirect has revealed a startling connection between periodontitis—chronic inflammation of the gums—and Alzheimer's disease.

The culprit? A bacterium called Porphyromonas gingivalis (P. gingivalis), one of the primary pathogens responsible for periodontal disease. Here's what makes this discovery so significant: researchers have detected P. gingivalis in the brainsof individuals with Alzheimer's disease. This isn't just correlation—the bacteria's toxic proteases (called gingipains) have been found co-localized with tau tangles and amyloid plaques in affected brain tissue.

Think about that for a moment. A bacterium from your mouth, making its way to your brain, potentially contributing to neurodegeneration. This underscores something I've been saying for years: oral health is brain health. The chronic inflammation from untreated gum disease doesn't stay in your mouth—it can travel systemically, cross the blood-brain barrier, and potentially set the stage for cognitive decline decades later.

The Spirochete Connection: Lyme Disease, Syphilis, and Dementia

Perhaps one of the most controversial yet compelling areas of research involves spirochetes—spiral-shaped bacteria that include Borrelia burgdorferi (the causative agent of Lyme disease) and Treponema pallidum (which causes syphilis).

We've known for over a century that late-stage syphilis can cause dementia, brain atrophy, and—remarkably—amyloid deposition that is virtually indistinguishable from Alzheimer's pathology. As one 2011 study in the Journal of Neuroinflammation powerfully states: “Each curly fiber corresponds to a single spirochete and each senile plaque to a spirochetal colony.”

More recent research has extended this connection to Lyme disease. Multiple studies have found:

• Borrelia burgdorferi DNA and antigens in the brains of Alzheimer's patients at rates 13 times higher than controls
• Spirochetes detected in over 90% of Alzheimer's cases when comprehensive detection methods are used
• Co-localization of Borrelia with amyloid and phospho-tau markers in brain tissue
• Evidence of Borrelia forming biofilms in the brain—making them particularly resistant to treatment

A 2022 study published in the Journal of Alzheimer's Disease found that Borrelia-positive aggregates co-localized with amyloid markers in Alzheimer's brain tissues, and when mammalian cells were infected with B. burgdorferi in the laboratory, there was a significant increase in amyloid-β and phospho-tau protein expression.

Having treated thousands of patients with Lyme disease and co-infections here in Colorado, I can tell you that the neurological manifestations are profound and often persist long after initial treatment. The brain fog, memory issues, and cognitive dysfunction I witness in my Lyme patients bear a striking resemblance to early dementia—and now we're beginning to understand why.

The Herpes Family: A Lifetime of Latent Infection

Perhaps the most extensively studied infectious connection to Alzheimer's involves the herpes simplex virus type 1 (HSV-1)—the virus that causes cold sores. Here's what makes this so relevant: an estimated 67% of the global population under age 50 is infected with HSV-1, and once infected, the virus remains in your body for life, residing latently in nerve cells.

The evidence linking HSV-1 to Alzheimer's is substantial and growing:

The APOE4 Connection

Research has consistently shown that HSV-1 in the brain, in combination with the APOE-ε4 genetic variant, dramatically increases Alzheimer's risk. This gene-environment interaction is crucial—it's not just about having the virus or the gene, but about how they interact to create the perfect storm for neurodegeneration.

Antiviral Protection

Perhaps most compelling is the epidemiological evidence: multiple large-scale studies have found that:

• Antiviral medications (valacyclovir and acyclovir) are associated with significantly reduced risk of Alzheimer's disease
• Treatment of herpes zoster (shingles) with antivirals reduces dementia risk
• Patients with HSV infections who receive antiviral treatment show 40-50% reduced risk of dementia compared to untreated patients

A January 2025 study in Scientific Reports examined participants from France and found that while HSV-1 seropositivity was widespread, those with suspected frequent HSV-1 reactivation (indicated by high antibody levels) showed lower cortical amyloid load, suggesting the immune response might be protective—but chronic reactivation could drive inflammation.

The Reactivation Problem

HSV-1 doesn't just lie dormant forever. It can periodically reactivate, particularly during times of:

• Stress
• Immune suppression
• Aging
• Other infections
• Head trauma

When HSV-1 reactivates in the brain, it triggers a cascade of inflammatory responses, activates microglia (the brain's immune cells), and promotes the production of amyloid-beta—potentially as an antimicrobial defense. A 2024 study published in Science Signaling found that repeated mechanical injury (mimicking concussions) reactivated latent HSV-1 in brain tissue models, triggering β-amyloid aggregation and other Alzheimer's-associated pathology in an IL-1β-dependent manner.

Other members of the herpes family implicated in dementia include:

• Varicella-zoster virus (VZV)—causes chickenpox and shingles
• Epstein-Barr virus (EBV)
• Cytomegalovirus (CMV)
• Human herpesvirus 6 (HHV-6)

The Transposable Elements Pathway

Groundbreaking 2025 research from Cleveland Clinic's Genome Center revealed a novel mechanism: HSV-1 can activate “jumping genes” called transposable elements (LINE-1) in our DNA. These elements make up nearly half of our genome and become more active as we age. When HSV-1 triggers their activation, they can disrupt key genetic processes associated with tau accumulation and Alzheimer's pathology. This discovery provides the first concrete evidence supporting the HSV-Alzheimer's link and identifies two FDA-approved drugs (valacyclovir and acyclovir) that can reverse this pathway in laboratory settings.

The Parasite Puzzle: Toxoplasma gondii

Here's something that might surprise you: approximately one-third of the world's population is infected with Toxoplasma gondii, a parasite typically contracted from undercooked meat or cat feces. Most people have no idea they're infected.

The connection to Alzheimer's is complex and somewhat contradictory:

The Risk Factor Evidence

• A 2021 Taiwan study found that patients with toxoplasmosis had an increased risk of developing dementia
• Research has shown T. gondii can alter NMDA receptor signaling and induce Alzheimer's-like signs in mice
• The parasite can trigger chronic neuroinflammation and interfere with normal brain metabolism

The Protective Paradox

Interestingly, some animal studies have shown that T. gondii infection can actually reduce amyloid plaque burden in Alzheimer's disease model mice by:

• Recruiting monocytes and activating microglia
• Enhancing phagocytic clearance of amyloid-beta
• Modulating the neuroimmune environment

However, a 2020 study published in Scientific Reports found that in aging mice, T. gondii was eventually cleared from the brain and had minimal long-term effects on cognition—suggesting the parasite's role may be more nuanced than initially thought.

The jury is still out on whether T. gondii is a net positive or negative for brain health, but the mere fact that it can influence Alzheimer's pathology highlights how deeply our microbial exposures shape our neurological destiny.

The Viral Roster: COVID-19, Influenza, and Beyond

The infectious hypothesis of Alzheimer's extends to numerous other viruses:

SARS-CoV-2

The COVID-19 pandemic has given us a real-time look at how viral infections can affect the brain. SARS-CoV-2 can:

• Enter the brain through the olfactory nerve
• Cross the disrupted blood-brain barrier
• Activate microglia and trigger neuroinflammation
• Increase oxidative stress through NADPH oxidase activation

We're already seeing reports of cognitive dysfunction (“brain fog”) persisting long after acute COVID-19 infection—and time will tell whether this increases long-term dementia risk.

Influenza and Other Respiratory Viruses

Multiple studies have linked influenza infection to increased dementia risk, while flu vaccination has been associated with reduced Alzheimer's incidence—adding to the evidence that infections play a causal role.

The Antimicrobial Protection Hypothesis

One of the most elegant explanations for all this data is the “antimicrobial protection hypothesis.” This framework proposes that:

1. Amyloid-beta has antimicrobial properties – It can directly combat bacteria, viruses, and fungi
2. Infections trigger amyloid production – When pathogens invade the brain, amyloid is produced as a defense mechanism
3. Chronic infection leads to chronic deposition – Persistent or recurring infections drive ongoing amyloid accumulation
4. Plaques are the battlefield – What we see as Alzheimer's pathology may be the debris of decades of immune warfare

This shifts our entire understanding of Alzheimer's from a disease of misfolded proteins to a disease of chronic infection and dysfunctional immune response. It explains why amyloid-targeting therapies have largely failed—we've been treating the symptom, not the cause.

The Multi-Hit Model: When Multiple Infections Collide

In my clinical practice, I rarely see patients with just one chronic infection. More commonly, they're dealing with a constellation of microbial challenges:

• Chronic Lyme disease with co-infections (Bartonella, Babesia)
• Reactivated herpes viruses (EBV, HSV, CMV)
• Fungal overgrowth and mold exposure
• Gut dysbiosis and intestinal permeability
• Periodontal disease

Research on “total infectious burden”—the cumulative effect of multiple infections—shows that cognitive decline correlates with the number of pathogens a person has been exposed to. It's not just about one microbe; it's about the chronic inflammatory state created by multiple, often subclinical, infections working in concert.

The Gut-Brain-Infection Axis

We can't discuss brain infections without acknowledging the gut-brain axis. Emerging research shows that:

• Gut dysbiosis can promote systemic inflammation that affects the brain
• Leaky gut allows bacterial components like lipopolysaccharide (LPS) to enter the bloodstream and cross the blood-brain barrier
• Periodontal bacteria can translocate to the gut, creating a mouth-gut-brain inflammatory circuit
• Short-chain fatty acids produced by beneficial gut bacteria (like butyrate) have neuroprotective effects by modulating microglial activation

When we support gut health, we're simultaneously supporting brain health and creating a less hospitable environment for pathogenic infections.

What This Means for Prevention and Treatment

This infectious model of Alzheimer's opens up exciting new possibilities for prevention and intervention:

1. Aggressive Infection Management

• Treat periodontal disease – Regular dental care, proper oral hygiene, and addressing active gum disease
• Address chronic Lyme and co-infections – Proper testing and comprehensive treatment protocols
• Manage herpes virus reactivation – Consider antiviral therapy for high-risk individuals, especially APOE-ε4 carriers
• Support immune function – Optimize vitamin D, zinc, and other nutrients essential for immune health

2. Reduce Inflammatory Load

• Optimize gut health – Probiotics, prebiotics, and healing leaky gut
• Address mold and biotoxin exposure – Environmental cleanup and detoxification
• Anti-inflammatory diet – Reduce processed foods, increase omega-3 fatty acids and polyphenols
• Stress management – Chronic stress reactivates latent viruses and suppresses immune function

3. Support the Blood-Brain Barrier

• Omega-3 fatty acids (especially DHA) – Essential for brain cell membranes and barrier integrity
• Magnesium L-threonate – The only form of magnesium proven to cross the blood-brain barrier
• Polyphenols – Compounds like resveratrol and curcumin support barrier function
• Sleep optimization – Deep sleep facilitates glymphatic drainage and brain detoxification

4. Neuroprotective Nutrients

Several nutrients show promise in protecting against infection-driven neurodegeneration:

• Phosphatidylcholine – Supports cell membrane health and repair; essential for brain cell integrity and communication
• Butyrate – Produced by gut bacteria, crosses into the brain to reduce neuroinflammation and support the gut-brain axis
• B vitamins (especially methylated forms) – Support methylation pathways crucial for detoxification and neurotransmitter production
• Glutathione – The master antioxidant for cellular protection; critical for detoxifying the brain

5. Emerging Therapies

The research is pointing toward several promising interventions:

• Repurposed antivirals – Acyclovir and valacyclovir show protection in epidemiological studies
• Antimicrobial peptides – May help clear chronic infections without antibiotic resistance
• Immune modulation – Targeting specific inflammatory pathways while preserving protective immunity
• Biofilm disruptors – Addressing the protective matrices that make infections so persistent

Recommended Products from Dr. Jill:

• Brain Mag – Magnesium L-threonate for cognitive support and blood-brain barrier health
• Omega Essentials DHA – High-potency DHA for brain health and neuroprotection
• Sodium Butyrate – Short-chain fatty acid for gut-brain axis support
• PC Liposomal Phospholipid Complex – Phosphatidylcholine for cellular and brain health
• Liposomal Glutathione – Master antioxidant for detoxification and cellular protection
• Methyl B-Complex – Activated B vitamins for methylation and energy support
• Probiotic Essentials with Saccharo – Comprehensive probiotic for gut microbiome balance

For additional reading, check out my other related blog articles: 

• 2 Surprising Facts About Alzheimer's: Mold Can Cause Alzheimer's & It's Reversible
• Lyme Disease & Breast Cancer Connection with Dr. John Oertle
• Persistent Post-Concussion Syndrome: Could Underlying Lyme Disease Be the True Culprit?
• The Gut-Brain Axis: How Your Microbiome Shapes Neuroinflammation and Mental Health
• Mold and Your Brain: The Surprising Connection Between Fungal Exposure and Neurological Health
• Could Autoimmune Encephalitis Be Caused by Mold, Lyme, and Hidden Infections?

My Personal and Professional Perspective

As someone who has personally recovered from both Crohn's disease and mold illness, and who sees patients daily struggling with complex chronic infections, this research resonates deeply with my clinical experience. I've witnessed firsthand how addressing underlying infections—whether it's Lyme disease, reactivated viruses, or mold-related illness—can dramatically improve cognitive function, energy, and overall neurological health.

The patients I see with the most severe “brain fog” and cognitive decline are almost always dealing with:

1. Chronic infections (often multiple)
2. Compromised gut health
3. Environmental toxin exposure
4. Mitochondrial dysfunction
5. Chronic inflammation

When we systematically address these root causes with a functional medicine approach, the results can be transformative. I've seen patients in their 60s and 70s regain mental clarity they thought was lost forever.

The Road Ahead: Research and Hope

The infectious hypothesis of Alzheimer's disease is gaining momentum, but we need:

• More clinical trials testing antivirals, antimicrobials, and immune-modulating therapies
• Better diagnostic tools to identify brain infections before symptoms appear
• Longitudinal studies tracking infections and cognitive outcomes over decades
• Mechanistic research clarifying exactly how each pathogen contributes to neurodegeneration

What's most exciting to me is that this paradigm shift offers actionable interventions. Unlike genetic risk factors we can't change, infections are potentially preventable and treatable. We have the tools—we just need the will to use them proactively.

Taking Action: Your Brain Health Checklist

Based on this research, here are practical steps you can take today:

Immediate Actions:

• [ ] Schedule a comprehensive dental exam and address any periodontal disease
• [ ] Optimize oral hygiene (brushing, flossing, antimicrobial mouthwash)
• [ ] Get tested for chronic infections if you have unexplained symptoms
• [ ] Support your gut microbiome with fermented foods and quality probiotics
• [ ] Ensure adequate omega-3 intake (aim for 1-2g EPA/DHA daily)

Ongoing Practices:

• [ ] Manage stress through meditation, yoga, or other mindfulness practices
• [ ] Prioritize 7-9 hours of quality sleep nightly
• [ ] Maintain an anti-inflammatory diet rich in vegetables, berries, and healthy fats
• [ ] Consider periodic fasting to support autophagy and immune function
• [ ] Stay socially and cognitively engaged

For High-Risk Individuals (APOE-ε4 carriers, family history, recurrent infections):

• [ ] Discuss preventive antiviral therapy with your healthcare provider
• [ ] Consider more aggressive infection screening and treatment
• [ ] Implement comprehensive neuroprotective supplement protocols
• [ ] Work with a functional medicine practitioner for personalized care

The Power of Faith and Resilience

As I share in my book Unexpected: Finding Resilience through Functional Medicine, Science, and Faith, healing is not just about protocols and supplements—it's about hope, resilience, and the profound belief that our bodies have an innate capacity to heal when given the right support.

The infectious model of Alzheimer's disease is not meant to frighten you, but to empower you. For the first time, we're beginning to understand the true root causes of this devastating disease, and with that understanding comes the possibility of genuine prevention.

Your brain is not destined to decline. With the right knowledge, support, and interventions, you can protect your cognitive health for decades to come.

Conclusion: A New Era of Hope

The evidence linking infections to Alzheimer's disease represents one of the most significant paradigm shifts in neuroscience in recent decades. From the bacteria in our mouths to the viruses lying dormant in our nerves, from parasites we didn't know we had to the gut microbiome that shapes our thoughts—we are finally seeing the bigger picture.

This isn't about creating fear around every infection or microbe. Rather, it's about recognizing that our health is deeply interconnected, that prevention matters, and that addressing root causes—not just symptoms—is the path to genuine healing.

As functional medicine physicians, our role is to be medical detectives, uncovering the hidden triggers of disease and supporting the body's innate healing capacity. The infectious origins of Alzheimer's disease give us new clues to follow, new interventions to explore, and most importantly, new hope to offer our patients.

The future of Alzheimer's prevention and treatment lies not in chasing plaques, but in supporting optimal immune function, addressing chronic infections, reducing inflammation, and creating the conditions for lifelong brain health.

And that future starts today, with each choice you make for your health.

If you're struggling with cognitive decline, brain fog, or chronic infections, I encourage you to seek out a functional medicine practitioner who can help you address the root causes of your symptoms. Together, we can change the trajectory of brain health—one person, one infection, one intervention at a time.

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Medical Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products mentioned in this article are not intended to diagnose, treat, cure, or prevent any disease. The information in this article is not intended to replace any recommendations or relationship with your physician. Please review the references cited for scientific support of any claims made.