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Lyme DiseaseLyme disease is a common infectious disorder that causes pain, fatigue, and muscle aches. It's caused by Borrelia burgdorferi, a bacterium that is transmitted to humans via the bite of infected blacklegged ticks. White-footed mice and other small woodland mammals are the main carriers of Lyme. White-tailed deer also act as hosts for disease-carrying ticks, but the quadrupeds don't become sick with the disease. Researchers estimate that more than 14% of the global population has contracted Lyme at some point. It can be debilitating, but it's treatable with antibiotics. First reported in 1975 among patients in Lyme, Connecticut, the disease can be hard to detect unless a patient develops and notices a skin rash. In the US, the economic burden of the disease is around $1B annually. As of early 2026, a potential Lyme vaccine was in late-stage clinical trials, and other efforts to slash the disease include a Massachusetts-based research project—first proposed for a trial on a private island—to genetically engineer mice using CRISPR to become immune to Lyme and then pass that trait on to their offspring.Explore Lyme Disease

Vector-Borne Diseases

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Lyme disease-causing bacteria predate any suspected biological weapons testingBorrelia bacteria existed long before any US biological weapons program—or human presence in North America. One study comparing genomes of the bacteria behind Lyme disease collected samples of the bacteria over three decades and calculated that the bacterium has been in North America longer than humans, at least 60,000 years. Other work found related bacteria preserved in amber from millions of years ago. Lyme disease is the most common vector-borne illness in the USIn the US, ticks account for 90% of all disease transmission from bites, including mosquitoes. And Lyme disease is the most common vector-borne disease in the US overall, with estimates suggesting there are about 475,000 Lyme cases annually across the nation. Johns Hopkins Bloomberg School of Public Health More than 1 in 7 people worldwide have had Lyme diseaseResearch published in 2022 suggests that 14.5% of the world's population has contracted Lyme disease. Researchers arrived at that estimate by analyzing the presence of Lyme disease antibodies (indicating prior infection) across 89 studies conducted between January 1984 and December 2021. The works collectively included blood samples from more than 150,000 people. (Some user may encounter a paywall.) New Scientist Lyme disease may cost about $1B annually in the USThe economic burden of the disease in this estimate includes direct medical costs and societal costs, including productivity losses. It does not include suspected, undiagnosed, or nonacute cases, which would push that figure upward. Yale School of Public Health Post-treatment Lyme disease syndrome may be caused by bacterial remnants in the liverPTLDS, which refers to lingering symptoms of Lyme after antibiotic treatment, is an area of active research. Rodent research published in 2025 suggests that these ongoing symptoms may potentially be due to the body's inflammatory response to lingering cellular components from the bacteria that cause Lyme, Borrelia burgdorferi. In rodents, components of the bacteria's cellular wall may remain in the liver after the bacteria were eliminated with antibiotics. Northwestern Medicine Blood tests for Lyme disease tend to come up as false negatives in the week after a biteIt can take several weeks for Lyme antibodies to develop, which is what blood tests would be detecting. That's why many clinicians will prescribe antibiotic treatment immediately after a bite if the individual develops the characteristic bullseye rash of Lyme or gets bitten in an area of the country known to have high rates of Lyme. Columbia University Irving Medical Center Read a study about racial differences in Lyme disease diagnosisThe research published in September 2025 examined differences in Lyme disease diagnosis among Medicaid and Medicare beneficiaries using data from 2016 to 2021. It notes that though US Lyme disease surveillance data indicates more than 90% of diagnosed Lyme cases are among white people, people of color—particularly those who identify as Black or African American—have higher rates of more severe disease of Lyme, with symptoms including arthritis and neurologic impacts. Emerging Infectious Diseases Deer don't get infected with Lyme disease—but ticks do feed on themAdult ticks feed on white-tailed deer and also lay eggs on the animals, but the deer don't get sick with Lyme disease. Research published in 2023 offered new insights into why deer don't get sick from Lyme disease: It appears that the quadruped may have specific not-yet-identified immune system proteins in their blood serum that kill the bacterium. CBC Genetic engineering mice is one idea to reduce Lyme disease transmissionWild white-footed mice are the main carriers of Lyme. A research team is hoping to genetically engineer mice, using CRISPR, to make the animals immune to Lyme. They're proposing a field trial where they would insert a gene with an antibody to Lyme infection to break the disease transmission cycle on a private island and then try it in Nantucket if that goes well. Simply killing the mice isn't an option because it would upend food webs. Unlike traditional vaccines, this "heritable immunization" would pass from one generation of mice to the next. 60 Minutes Two Lyme disease vaccines were in development in 2026As of early 2026, there was no vaccine for Lyme disease available. One candidate vaccine, VLA15, was in later-stage clinical trials. Another designed to provide seasonal protection was licensed to a pharmaceutical company in 2025, and was planned for human clinical trials. US Centers for Disease Control and Prevention See the incidence of Lyme disease across all 50 states in 2023The US states with the highest rate of Lyme disease—meaning cases per 100,000 people—were Rhode Island, Vermont, and Maine, in 2023. Rhode Island had 260 cases per 100,000 people, based on cases reported to the US Centers for Disease Control and Prevention. (Some users may encounter a paywall.) Statista Search Lyme disease incidence in your countyThe searchable database at the bottom of this webpage allows users to check the reported incidence of Lyme disease in US counties and Canadian health regions. In 2022, for example, Baltimore County in Maryland had a rate of about 34 probable and confirmed cases per 100,000 people. Arlington, County in Virginia was less than half of that for the same time period. Johns Hopkins Bloomberg School of Public Health Lyme disease is caused by bacteria transmitted through the bite of infected ticksIt's an infectious disease caused by Borrelia burgdorferi bacteria. It's spread through the bite of two species of infected ticks, the Western blacklegged ticks on the West Coast, and Blacklegged ticks found throughout the eastern US. The ticks can transmit the disease at both the nymph and adult stage. It's not known to be transmitted from one person to another via kissing or sex. California Department of Public Health Lyme disease was first identified in Lyme, Connecticut in 1975A cluster of 51 children and adults in the town all began experiencing uncommon arthritic symptoms and the cases were reported to the state health department. A quarter of the cases were preceded by a skin lesion. The patients tended to live near the woods. Connecticut Department of Health More than 20 mosquito-borne and tick-borne diseases are found in the USChildren, older adults, and people with compromised immune systems are at particular risk of poorer health outcomes from these diseases. But dog owners and outdoor enthusiasts are among those at particular risk of contracting these illnesses, which include Lyme disease, Zika, and the condition Alpha-gal Syndrome. US Centers for Disease Control and Prevention Erythema migrans rash is common in Lyme—but it often doesn't look like a bull's-eyeThe US Centers for Disease Control and Prevention states that this rash occurs in roughly 70% or more of Lyme disease patients, and typically occurs at the site of a tick bite. The rash may expand slowly over several days and feel warm to the touch, but it's rarely itchy or painful. As it grows, areas of it may clear—creating a target or "bull's-eye" appearance. US Centers for Disease Control and Prevention Land use changes in Connecticut may have helped to enable Lyme's leap into humansForest clearing and fragmentation, alongside suburban development, may have contributed to the emergence of Lyme disease in humans in the 1970s. Those changes brought mice, carriers of the disease, into greater contact with people. Climate change is also facilitating Lyme's spread as tick populations survive milder winters and move northward. Mongabay Chronic lyme isn't a medically recognized diagnosis in conventional medicineIt describes a constellation of symptoms attributed to a persistent Lyme infection—meaning the bacteria have remained present even after antibiotics. It often occurs among people who have never received a positive test for Lyme. Doctors do recognize "post-treatment Lyme disease syndrome," however, which can include muscle and joint pain, fatigue, and cognitive difficulties after treatment for confirmed Lyme. CBC Nonwhite Lyme patients tend to be diagnosed later and have more severe diseasePeer-reviewed research published in 2025 from Pfizer—a pharmaceutical company working on a candidate vaccine for Lyme disease—examined Lyme data from more than 150,000 Medicare and Medicaid beneficiaries and found that Black patients, as compared to white beneficiaries, were more likely to have disease that had spread further throughout the body at the time of care. The difference, the scientists wrote, may be partly due to difficulties recognizing the characteristic rash on darker-colored skin. Pfizer See the total number of Lyme cases per state in 2023New York, Pennsylvania, and Massachusetts had the highest total number of Lyme disease cases in 2023. New York had more than 22,000 cases that year. Maine had one of the highest Lyme incidence rates of disease that year—213 per 100,000 people—but only 2,942 cases overall. Statista Watch the safe way to remove a tick from your bodyMinimizing your risk of Lyme and other tickborne diseases hinges on quickly removing ticks. To do so, place tweezers on the animal as close to the skin as possible and then pull directly upwards to try to avoid leaving bits of the tick's body behind. If possible, try to take a photo of the tick to share with your doctor to better identify potential disease risks (since certain tick species can carry specific diseases). Next, dispose of the tick without crushing it in your fingers—flushing it down the toilet, or placing it in alcohol or a sealed bag—and then thoroughly wash the bite area and your hands. US Centers for Disease Control and Prevention Ticks must typically be attached to a person for more than 24 hours to transmit LymeInfected blacklegged ticks must typically be attached to a person for more than 24 hours—and often closer to 36—to transmit Lyme. That period is enough time for the bacteria that causes Lyme to migrate from the tick's gut into the person's bloodstream while it's latched on through its bite. (There are rare documented cases of transmission under 24 hours.) Rapid removal of the tick is key to disease prevention. New York State Department of Public Health

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