"The term 'chronic Lyme disease' isn't supported by current medical evidence," Scott said. "When patients tell me about ongoing fatigue, pain, and cognitive difficulties, I believe them completely. These symptoms are real and debilitating. But the science shows us these aren't caused by persistent Lyme bacteria, so we need to look for other treatable causes."

Scott spoke about the common misperceptions surrounding tick-borne illness, how geography plays a role and progress toward vaccines. He also addressed the challenges of treating patients who are desperate for a clear diagnosis in an environment saturated with misinformation, and the role of high-profile cases, like the recent story about Justin Timberlake’s “chronic Lyme,” that flood headlines.

What should people know about tick-borne diseases?

Nationally, tick-borne diseases overall increased about 25% from 2011 to 2019, the last year for which we have reliable numbers due to pandemic-related disruptions. Warmer climates, booming deer and rodent populations, and the growth of suburbs have all expanded tick habitats and human exposure, while greater awareness also makes more cases visible.

Cases of babesiosis, another tick-borne disease, have also risen significantly in the United States. From 2011 to 2019, babesiosis cases in the northeastern U.S. rose sharply—by 1,422% in Maine, 1,602% in Vermont, and 372% in New Hampshire—prompting the CDC to classify these states as newly endemic. Untreated, babesiosis can cause fever, chills, fatigue, muscle aches and anemia.

Lyme, still by far the most common of these diseases, can usually be prevented with a single dose of the antibiotic doxycycline. Delivered within three days after a high-risk tick bite, the treatment is 87% effective. Even if a Lyme infection sets in, it is usually very treatable with a single course of standard antibiotics.

What role does geography play?

The picture in California is quite different from that in the Northeast. Western tick species and ecology aren’t as conducive to these diseases. California ticks have much lower infection rates. Studies show that less than 2% carry Lyme bacteria, and only 0.3% carry the bacterium that causes anaplasmosis, another bacterial infection transmitted by the same black-legged ticks that spread Lyme and babesiosis.

Climate change is expanding some tick ranges, but not everywhere. Ecology matters more than temperature. California’s hot, dry summers, for example, reduce tick survival compared with the humid Northeast. What’s more, California’s reservoir hosts (the animals that maintain the bacteria in nature) are different. The native Western fence lizards and alligator lizards, for example, clear infection from ticks that feed on them, a natural protection the Northeast doesn’t have. So, Lyme and other tick-borne illnesses are still rare in California.

What has changed dramatically is the number of people coming to my clinic at Stanford convinced they have Lyme. There's more awareness now, but unfortunately also a lot of misinformation. I'm seeing many more patients who were told by alternative providers that they have chronic Lyme based on unvalidated tests or non-specific symptoms.

The perception of Lyme disease has grown much more than the actual incidence has. My role increasingly involves separating the signal from the noise. I spend a lot of time educating both patients and other physicians about what the science really shows regarding tick-borne diseases.

Elsewhere in the country ticks and the diseases they carry appear to be adapting to new climate and ecological conditions. In the Northwest, western blacklegged ticks are spreading inland and north, increasing Lyme and anaplasmosis in Washington, Oregon, and Idaho. In the Midwest, blacklegged ticks are expanding west and north, driving up Lyme, babesiosis, and anaplasmosis in Minnesota, Wisconsin, and the Dakotas.

In the South, rising lone star tick populations are pushing ehrlichiosis, STARI, and red-meat allergy (alpha-gal syndrome) farther north and west. In the Southwest, brown dog ticks continue to cause Rocky Mountain spotted fever outbreaks.

Where does the impression that “chronic Lyme” is a huge problem come from?   

There’s an entire industry of self-described “Lyme-literate” practitioners and specialty testing companies that actively promote the idea that Lyme is everywhere and severely underdiagnosed. Social media amplifies dramatic patient stories, like Justin Timberlake’s, making rare California cases seem common and even almost fashionable.

While the internet is full of stories about “chronic Lyme,” the science shows a much more limited problem. Even in high-endemic areas like the Northeast, the CDC data show that six months after treatment, compared with controls, only 5% to 10% of properly treated patients develop persistent symptoms. But that isn’t an ongoing infection — multiple studies show that no viable bacteria remain.

The symptoms likely result from inflammatory aftermath, similar to how some people have lingering effects after COVID-19 or other infections, even when the infections have resolved. The great majority of people who believe they have “chronic Lyme” either never had Lyme, or they had it and now suffer from symptoms caused by other conditions.

What are the costs of the popular misperceptions about Lyme?

Studies show that patients diagnosed with “chronic Lyme” often receive months or years of antibiotics, with some getting over 200 days of treatment annually — far beyond any evidence-based recommendations.

A 2017 Stanford Medicine case series described five patients who developed serious complications from treatments for so-called “chronic Lyme disease” — including a life-threatening whole-body infection from an intravenous catheter (one patient died), a spinal bone infection caused by bacteria in the blood, a severe intestinal infection from C. difficile bacteria, and an infected abscess adjacent to the spine.

The report emphasizes that prolonged intravenous antibiotics and immunoglobulin treatments lack proven benefit and can cause substantial harm; standard Lyme disease therapy remains a two- to four-week antibiotic course. The case series urges clinicians and public health officials to recognize these risks and calls for systematic tracking of adverse events tied to such unproven “chronic Lyme” treatments.

What conditions are misdiagnosed as “chronic Lyme”?

Many conditions can cause fatigue, body aches and cognitive problems, including other infections, depression, diabetes, thyroid disorders, fibromyalgia, autoimmune diseases like lupus, vitamin deficiencies, sleep apnea and multiple sclerosis. It’s especially unlikely to be Lyme if someone tested negative or hasn’t been in endemic areas.

How can physicians best help patients who come to them believing they have “chronic Lyme”?

The first challenge is distinguishing between patients who have Lyme disease and those with persistent symptoms incorrectly attributed to it. Many patients arrive at the clinic with positive results from non-FDA-approved “Lyme specialty” labs that produce false positives. But true Lyme is diagnosed using CDC-recommended two-tiered testing with Food and Drug Administration-approved assays.

For patients who have ongoing problems but no clear evidence of active infection, the hardest part for a physician is validating that their symptoms are real while being honest about the diagnosis. I then work hard to identify the actual cause of their symptoms and to connect them with appropriate specialists, emphasizing that finding the real cause leads to more effective treatment than continuing to chase a Lyme diagnosis that isn’t there.

When talking with other physicians, I emphasize the importance of using only FDA-approved, validated testing methods and following evidence-based treatment guidelines. We must resist pressure from patients to order unvalidated tests or prescribe prolonged antibiotic courses that can cause more harm than benefit. And the medical community needs to better address the real suffering of patients with persistent symptoms while maintaining scientific rigor in diagnosis and treatment.

What about Lyme vaccines?

The most promising development is Pfizer and Valneva’s new Lyme vaccine, VLA15, currently in Phase 3 trials. It targets different bacterial proteins than a previous vaccine, avoiding the autoimmune concerns that led to its withdrawal. There’s also research into “anti-tick” vaccines that would make our immune systems react to proteins in tick saliva, potentially protecting against multiple tick-borne diseases by triggering itching, redness and inflammation at the site of the bite, thus interfering with the tick’s ability to stay attached and feed long enough to infect.

On the diagnostic front, the FDA recently cleared a new Lyme test that could streamline diagnosis, and researchers are developing artificial intelligence-based tests that might give results in minutes rather than days, preventing progression to later-stage disease and reducing the window for misinformation to take hold.

How can we protect ourselves while spending time outdoors?

The precautions are simple and safe, and they protect against multiple diseases — not just Lyme. Using DEET repellent and staying on trails are all smart practices anywhere ticks live. Check yourself for ticks after time in the outdoors: Removing ticks within 24 hours usually prevents infection. See a doctor if you develop a rash (especially a bull’s-eye rash), flu-like symptoms, or unusual neurological or joint problems after a tick bite. Also seek medical care if you have a compromised immune system.