Lyme disease is a multi-system bacterial infection caused by the spirochete, Borrelia burgdorferi, which is transmitted to humans through the bite of an infected deer tick. Lyme disease has several different stages: first stage (acute/early localized), second stage (early disseminated), and third stage (chronic/late disseminated). Symptoms vary depending on the stage of illness. In early Lyme disease, patients can present with a rash and/or flu-like symptoms. In later stages symptoms can manifest in multiple body systems, including musculoskeletal, heart, brain, and nervous system.
How has Lyme disease expanded since its first discovery?
Lyme disease, was first discovered in the United States in Lyme, Connecticut, in the mid-1970s and is now the most common US vector-borne disease. The estimated cumulative number of Americans struggling with chronic symptoms relating to Lyme disease may be as high as 1.9 million in 2020.
The number of new cases in the US exceeds 476,000 a year.
Lyme disease is spreading geographically and is hyper-endemic in the northeast and mid-Atlantic, upper Great Lakes region, and west coast. The ticks that transmit Lyme disease have been found in half of all US counties. Lyme disease is a worldwide health epidemic and a growing problem in regions such as Canada, Europe, and Asia.
Lyme disease is spreading geographically, as illustrated by the CDC maps below.
Reported Cases of Lyme Disease- United States, 2018
Note that Massachusetts, an endemic state, is no longer reporting Lyme Disease cases
Reported Cases of Lyme Disease- United States, 2001
Ticks that Transmit Lyme Disease are spreading geographically and are found in half of US Counties.
Map A shows tick distributions 1907-1996. Map B shows 1907-2015.
Distribution by county of recorded presence of I. scapularis and I. pacificus in the continental United States (a) 1907–1996 (from Dennis et al. 1998 ), (b) 1907–2015. Counties classified as established (red or green) for a given tick species had at least six ticks or two life stages recorded within a single calendar year. Counties with fewer ticks of a single life stage were classified as reported (blue or yellow) for the tick species. Counties shown in white indicate“no records.”
What causes Lyme Disease?
Lyme disease is transmitted by the bite of an infected black-legged tick, otherwise known as a deer tick. The infective agent of Lyme disease, the spirochete bacteria, Borrelia burgdorferi, is an obligate parasite of animals and requires animal reservoirs, such as mice, to survive. Ticks transmit Borrelia burgdorferi between animals including mice, small rodents, birds, some reptiles, pets, and people. There are numerous genotypes of Borrelia burgdorferi that are associated with different degrees of virulence.
Black-legged ticks can also transmit other infectious agents such as Anaplasma, Babesia, and Powassan virus. In addition, there are other species of borrelia that cause Lyme-like illnesses including Borrelia mayonii, and the relapsing fever like organism, Borrelia miyamotoi. Other tick-borne illnesses include Ehrlichiosis, Rocky Mountain Spotted Fever (& other Rickettsias), and Southern Tick-Associated Rash Illness (STARI). Another condition is alpha-gal meat allergy that occurs in some individuals previously bitten by a lone-star tick.
Can tick-borne disease be life-threatening?
Some tick-borne conditions can be serious or life-threatening and may warrant immediate medical attention including Lyme carditis, Lyme meningitis, Powassan virus, Rocky Mountain spotted fever, Ehrlichiosis, and alpha-gal allergy.