Infectolab - Lyme terms

A Glossary of Lyme Disease Terms

Lyme has always been a tricky disease to get a handle on, for both patients and doctors alike. There is a lot of misinformation swirling around the diagnosis and treatment of Lyme disease, and although it has become more prominent in recent years, many prospective patients still don’t know exactly what they’re dealing with, how they got it, or what their treatment path might be. Among all this mystery, one thing is certain: Lyme is the fastest growing vector-borne disease in America. Previously only found in northeastern states, the disease has now surfaced in every single state in mainland U.S. As the country faces down this growing Lyme epidemic, education is an important tool in fighting back. This glossary of Lyme disease terms provides a good place to start. 

Acute Lyme disease

This is the term given to the primary stage of Lyme disease. It generally lasts a few weeks, and includes symptoms like congestion, fatigue, headaches, and muscle stiffness, which may be mistaken for flu.

Chronic Lyme disease

A blanket term used to describe the set of symptoms that evolves from an untreated infection. When acute Lyme disease is left untreated, the bacteria will embed itself further in the body and progress to the chronic stage. This can result in a whole host of various symptoms, which largely comprises debilitating fatigue, joint soreness, impaired mobility, and decreased neurological capacity, and can also include depression, anxiety, partial paralysis, and heart problems. Chronic Lyme disease is only selectively recognized as a legitimate disorder by the CDC, who prefer to categorize the disease by its symptoms. Because of this, many doctors are not literate in its diagnosis or treatment.


The Center for Disease Prevention and Control, a federal agency that conducts research on various disorders and supports health promotion across the country. The CDC prefers to categorize Lyme disease in accordance with the symptoms, and will rarely use the unspecific term “chronic Lyme,” which leads to confusion in both medical and patient circles.

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There is some confusion about chronic Lyme disease in medical spheres due to the way the CDC chooses to categorize it.


The name given to any parasitic bacterium of the genus Borrelia, certain strains of which are pathogenic to humans. The fundamental cause of Lyme, this bacteria is transmitted to humans via tick bite.


The term given to an infection or disease caused by a spirochete of the Borrelia genus. There can be a number of different types of borreliosis, including neuroborreliosis and cardiac borreliosis. All conditions that fall under the borreliosis umbrella can also be described as “chronic Lyme infection.”

Bullseye rash

The name for the distinctive rash that appears after a Lyme-infected tick bite. It constitutes a red area surrounded by a red ring. This is the only surefire symptom of Lyme disease; if it’s caught early by the patient, then the infection can usually be cured by antibiotics.

Deer tick

Ixodes scapularis, also known as the black-legged tick, is the main cause of the spread of Lyme, and transmits the disease in the northeast and mid-west of America. The western black-legged tick is responsible for spreading the disease on the west coast. Not all deer ticks carry the borrelia bacteria; it’s estimated to be one in three.

Tick season

Traditionally, tick season lasted from May to September, as ticks couldn’t survive the cooler temperatures of fall and winter. Recently, though, thanks to global warming, the tick population has become more prevalent, and can now exist beyond the established tick season. Experts have declared that tick season should now start in April instead of May.


The main component of Lyme disease, infection is what happens when the borrelia bacteria invade the host’s system. If Lyme progresses to its chronic form, then the infection is much harder to eradicate.


Inflammation is the other component of Lyme disease, and is the thing that causes most symptoms in patients with chronic Lyme. Inflammation is the body’s reaction to the infection. It involves immune cells releasing cytokines to communicate with each other in a joint effort to clear the body of the infecting pathogen. Cytokines can cause defensive responses such as swelling, inducing fever, and recruiting immune cells to the site of infection. If a pathogen is not cleared, it can lead to chronic inflammation that can provoke debilitating symptoms such as aching joints and loss of mobility.

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Fever, swelling, and joint pain are all signs of inflammation.


Sometimes Lyme is not present on its own – it can be transmitted along with other infections, or an infection can cause a dormant disease to spur up again. When these exist at the same time as Lyme, they are known as co-infections. They can make the main infection much harder to shake, or increase the severity of the symptoms. Some common co-infections found in Lyme disease patients include babesiosis, anaplasmosis, and ehrlichiosis.

Immune system

The part of the body that’s triggered by the invading bacteria, provoking an automatic response. The immune system consists of multiple branches and a diverse set of cells. It includes an innate response that is triggered upon invasion of a pathogen as a first line of defense and the adoptive immune system that needs time to generate an antigen-specific response, reflected in the antibodies produced and in the cellular response of antigen-specific T cells. If an infection occurs where the pathogen is capable of evading the immune system, it can lead to a chronic disease. In that case, it depends whether it is a controlled infection or a non-controlled infection. Chronic conditions can come with chronic inflammation, as the immune system will constantly encounter antigens that keep it active.

T cells

A valuable part of the immune system, which recognizes foreign invaders in the body via a special system called a T cell receptor. There are various types of T cells, all with different functions; they comprise critical aspects of our overall adaptive immune systems. The subsets of T cells are very diverse and their function and cytokine expression patterns vary depending on the communication signals they receive and which subset they differentiate into. The classic T cell in the context of a bacterial infection belongs to the class of TH-1 helper cells. Their primary function is to present antigens to the B cells and help them generate antigen-specific antibodies that recognize the pathogen. Other T cells are effector cells; these migrate to the site of infection and help fight the pathogen in the affected tissue. Furthermore, T cells can be memory cells that are reactivated upon a second infection and will improve the immune response.

White blood cells

These are the cells of the immune system that are involved in fighting infection. They are found in the blood and lymph tissue, and work to eradicate foreign invaders in the body. They include T cells, B cells, macrophages, NK cells, and other adaptive and innate immune cells.

Multiple Sclerosis

One of the disorders that chronic Lyme is routinely misdiagnosed as. Other common misdiagnoses include fibromyalgia and chronic fatigue syndrome.

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