The distinction between the two virus stories on this page is clinically important. Tick-borne viruses are transmitted the same way as Lyme — through a bite. Reactivated viruses, like EBV or HHV-6, were already present in the body long before the tick bite. What Lyme disease does is weaken the immune surveillance that kept them suppressed. Understanding which viruses belong to which category changes how you think about treatment and recovery.
Powassan virus — the fast one
Powassan is the most dangerous virus transmitted by the same Ixodes ticks that carry Lyme disease in North America. Cases are still relatively rare — but they are increasing year on year, and the virus has a unique and frightening characteristic: it can transmit within minutes of the tick beginning to feed, long before the 24–36 hours typically required for Borrelia transmission.
Symptoms begin 1–5 weeks after infection: fever, headache, vomiting, progressing to encephalitis, seizures, and respiratory failure in severe cases. There is no specific treatment or vaccine. Of those who survive, roughly half carry permanent neurological damage — memory loss, recurrent headaches, muscle weakness, cognitive impairment.
The standard advice to remove ticks promptly provides real protection against Lyme disease — but essentially no protection against Powassan. This is the clearest argument for tick prevention before exposure, not just tick removal after attachment.
Heartland & Bourbon viruses — America's newest tick threats
First identified in Missouri in 2009, Heartland virus is transmitted by the Lone Star tick — the same tick that carries Ehrlichia and can trigger alpha-gal syndrome. Its symptoms closely mimic Ehrlichiosis: fever, fatigue, loss of appetite, headache, muscle aches, low white blood cell count, low platelet count, and elevated liver enzymes. This overlap means it can easily be misidentified — and standard Ehrlichia tests return negative.
Most patients require hospitalisation. The majority recover fully, though some deaths have been reported — particularly in older patients or those with underlying conditions. More than 50 cases had been confirmed as of 2020, but this is certainly an undercount given diagnostic challenges. No specific treatment or vaccine exists; supportive care is the only option.
The Bourbon virus is one of the most recently discovered tick-borne viruses in the Western hemisphere — identified in 2014 in Bourbon County, Kansas, when a farmer who had removed multiple ticks developed a severe febrile illness that killed him after 11 days. Extensive testing for known bacterial and viral causes came back negative; the virus was identified as an entirely novel organism — a thogotovirus, a type previously unknown in the Americas.
The symptoms mirror Heartland virus: fever, headache, fatigue, muscle and joint pain, rash, and the same characteristic laboratory pattern of leukopenia and thrombocytopenia. Tick transmission is presumed but not yet formally proven. Cases remain very rare, but the fact that it went undetected until 2014 raises questions about what else is circulating unrecognised in tick populations.
Colorado tick fever — the classic western virus
Colorado tick fever has been recognised for much longer than the emerging viruses above. It causes a characteristic biphasic illness — two to three days of fever, headache, chills, and muscle pain, followed by a brief improvement, then a second fever episode lasting several more days. This saddle-back pattern is clinically distinctive when recognised.
Most cases resolve fully without treatment. Serious complications including meningitis, encephalitis, and haemorrhagic fever occur in a small minority, primarily in children. The virus can infect red blood cells directly, where it persists for weeks — meaning blood donors who have recently had Colorado tick fever can transmit the virus through transfusion. No vaccine or specific antiviral treatment exists.
In regions where multiple tick species coexist — such as the northeastern United States where Ixodes and Lone Star ticks both circulate — a patient may have exposure to both bacterial and viral tick-borne pathogens in a single season. When the clinical picture doesn't fit a single diagnosis, or when bacterial treatment produces no improvement, viral co-infection should be on the differential. Standard Lyme treatment has no effect on any of these viruses.
Why Lyme disease reactivates dormant viruses
Herpesviruses are a family of DNA viruses with a defining characteristic: after initial infection, they establish lifelong latency in specific host cells. The immune system maintains constant low-level surveillance to keep them suppressed — but it requires ongoing immunological resources to do so. When those resources are redirected or depleted, the viruses seize the opportunity.
The reactivation cascade
Dr. Richard Horowitz, one of the leading LLMD clinicians, screens all chronic Lyme patients for viral co-infections — particularly when fatigue is disproportionate to other findings. He notes that EBV and HHV-6 in particular appear regularly in patients who are not improving on antibiotic therapy alone.
The key clinical consequence: antibiotics — even appropriate, well-targeted Lyme antibiotics — cannot treat viral infections. If a patient has active Lyme disease and reactivated EBV, the antibiotic addresses the bacterial component but leaves the viral component entirely untouched. This can explain why some patients plateau on antibiotic treatment, feeling partially better but never fully recovering.
EBV, HHV-6, CMV & VZV — the sleeping giants
All four of the following viruses are members of the herpesvirus family. All establish lifelong latency after initial infection. All can reactivate under conditions of immune stress. And all produce symptom patterns that significantly overlap with — and can be mistaken for — Lyme disease.
Infects approximately 95% of adults worldwide. The cause of infectious mononucleosis (glandular fever). After primary infection, EBV establishes lifelong latency inside B lymphocytes — the same immune cells that produce antibodies against Lyme disease. When EBV reactivates in a Lyme patient, it can cause chronic fatigue, swollen lymph nodes, sore throat, cognitive dysfunction, and a second round of immune disruption that compounds the Lyme picture. High EBV antibody titers are frequently found in chronic Lyme patients. Critically, EBV can also cause false-positive mononucleosis tests — and Lyme disease can cause cross-reactive antibodies that produce false-positive EBV results. This bidirectional confusion delays diagnosis on both sides.
Primary infection typically occurs in early childhood — it causes roseola, the common febrile rash illness of infants. After that, HHV-6 remains latent in monocytes and macrophages for life. When reactivated, HHV-6 is both immune-suppressive and capable of activating other viruses — including EBV. It has been specifically linked to chronic fatigue syndrome and fibromyalgia, both of which share extensive symptom overlap with chronic Lyme. Elevated HHV-6 levels are found commonly in chronic Lyme patients at specialist testing laboratories. HHV-6 is considered a possible cofactor in multiple sclerosis, ADD, and autism spectrum disorder — all of which show higher rates in Lyme-endemic regions.
Another near-universal human infection — up to 80% of adults carry CMV in latency. Primary infection is usually asymptomatic or produces a mild mononucleosis-like illness. CMV establishes latency in monocytes and myeloid progenitor cells. Reactivation in Lyme patients can cause prolonged fatigue, immune dysregulation, and inflammatory symptoms that are clinically indistinguishable from Lyme flares. Like EBV, CMV can produce cross-reactive antibodies that complicate interpretation of Lyme serological tests. It is regularly included in the viral screening panel used by LLMD practitioners for patients who are not responding to antibiotic treatment.
The cause of chickenpox (varicella) in primary infection. After resolution, VZV retreats to sensory nerve ganglia throughout the body — where it can remain for decades. Reactivation produces shingles (herpes zoster): intense, burning pain following a nerve distribution, often accompanied by a blistering rash on one side of the body. In immunocompromised patients — including those with chronic Lyme — shingles can be more severe, more widespread, and more likely to produce post-herpetic neuralgia (chronic nerve pain lasting months or years after the rash resolves). A Lyme patient who develops shingles during or after treatment may be experiencing immune suppression allowing VZV reactivation.
How to approach viral co-infections in Lyme patients
Dr. Marty Ross, an LLMD practitioner with extensive chronic Lyme experience, recommends a pragmatic approach: focus on Lyme and bacterial co-infections first. If a patient has not made meaningful progress after 6–9 months of appropriate treatment, then screen for viral co-infections — particularly EBV, HHV-6, CMV, and parvovirus B19.
Standard IgG antibody tests for EBV, HHV-6, and CMV will always be positive in anyone who has had these infections — because IgG antibodies are permanent markers of past exposure. The relevant question is whether the virus is currently active. Active reactivation is better indicated by elevated IgM (acute response) antibodies, PCR showing viral DNA in the blood, or T-cell studies showing ongoing immune activation against the virus. A positive IgG alone does not confirm active reactivation.
There are no widely effective conventional antivirals for most of these herpesvirus reactivations in the context of chronic illness. The primary strategy is immune support — because a stronger immune system is the most effective suppressor of latent viruses. This means addressing the underlying Lyme infection, reducing inflammatory burden, supporting mitochondrial function, and using immune-modulating supplements. Some practitioners use targeted antivirals in specific cases, particularly for EBV (valacyclovir) or CMV (valganciclovir), but evidence for chronic use is limited. The most consistent observation from experienced LLMD practitioners is that patients' viral burden often reduces significantly once the bacterial infections are adequately treated and immune function begins to recover.
EBV reactivation can cause false-positive mononucleosis test results — and Lyme disease can produce cross-reactive antibodies that look like EBV on certain panels. This means a patient presenting with fatigue, swollen lymph nodes, and a positive EBV test may actually have Lyme disease. And a patient diagnosed with Lyme may have concurrent active EBV that is driving much of their fatigue. The two conditions share enough overlapping symptoms — and enough overlapping laboratory noise — that distinguishing them requires careful clinical assessment, not just a single positive test result.
Why viruses matter in chronic Lyme recovery
If you are a Lyme patient who has been on appropriate antibiotic treatment for months and is not recovering as expected — if fatigue remains disproportionate, if cognitive symptoms persist, if the illness feels layered and complex — viral co-infections are a legitimate part of the investigation. Not because they are more important than the bacteria, but because they can be a second engine driving the illness that no amount of antibiotics will switch off.
This is not a fringe position. It is the clinical experience reported by Dr. Horowitz, Dr. Ross, and many other LLMD practitioners who see thousands of chronic Lyme patients. The viral layer is real, it is measurable, and it deserves to be part of the conversation.
Sources & further reading
- Horowitz R. — Why Can't I Get Better? Viral infections and chronic MSIDS. LymeDisease.org
- Ross M. — Chronic Viruses: A Brief Guide. TreatLyme.com
- Cameron D. — When Lyme Disease Causes a Positive Test for Mononucleosis. danielcameronmd.com, 2026
- Portland Clinic of Natural Health — Tick-Borne Illnesses and Reactivated Epstein-Barr Virus, 2023
- Maderis T. — Epstein-Barr Virus in Chronic Fatigue Syndrome and Autoimmune Diseases. drtoddmaderis.com, 2026
- PMC10892980 — Heartland Virus Disease: An Underreported Emerging Infection
- Wikipedia — Bourbon virus; Colorado tick fever; Heartland virus; Powassan virus
- CDC — About ticks and tick-borne diseases
Last updated: April 2026