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Lyme disease

This Factsheet is also available as a pdf.


Lyme disease (or Lyme borreliosis) is caused by the bite of a tick infected with certain Borrelia bacteria with cases generally restricted to Europe (including the UK) and North America. Symptoms are often mild and can be effectively treated with antibiotics, but severe and long-lasting symptoms may develop if treatment is delayed or missed.



  • Awareness of Lyme disease has grown recently but there are misconceptions and controversy around:
  • The diagnosis of Lyme disease, particularly around which are the best diagnostic tests to use;
  • The type and duration of treatment, especially whether short courses of antibiotics are sufficient to clear the infection or whether more prolonged treatment is required;
  • What causes chronic symptoms such as fatigue, myalgia etc. following a Borrelia infection;
  • ‘Chronic Lyme disease’: there is no medically accepted definition and disagreement over diagnosis and its existence as a defined medical condition.



  • Across the UK – 0-15% of hard-bodied ticks may be infected with the Borrelia bacteria which cause Lyme disease.
  • Ticks which are infected with Lyme-causing bacteria can infect humans by biting them. Cases of Lyme disease tend to peak during the summer months but can occur throughout the year.
  • Infected ticks are present across the UK including in areas such as Exmoor, the New Forest, and the Scottish Highlands, but the risk of exposure to Lyme disease is not just limited to these locations.
  • Ticks are common in wooded and heath areas but may be found in any green spaces, including urban parks and gardens, and attach themselves to humans and animals through physical contact as they don’t jump or fly.
  • Ticks can be as small as a pinhead and their bites are not painful, so may not be easily noticed. Also, they may bite in inaccessible places such as the scalp or groin.
  • The longer a feeding tick remains attached, the more likely the chance of infection being transmitted. It is therefore important to remove ticks promptly if you are bitten.
  • There is currently no vaccine available to prevent Lyme disease but sensible preventative measures can be taken when visiting at-risk areas.
  • There is no reliable evidence for transmission of Lyme disease from person-to-person, either sexually or from mother to child.
  • There is no evidence that insects other than ticks (mosquitoes, flies, spiders etc.) transmit Lyme disease.



  • Around two thirds of early-stage Lyme disease cases present with a spreading circular rash which is often referred to as a bullseye rash, but may vary in appearance.
  • There are often associated general symptoms similar to those of flu, such as fever, chills, aches and pain and muscle stiffness. These may occur even if a rash is absent.
  • If early Lyme disease is not treated then more serious symptoms can develop in the following weeks, months or years. These can include neurological symptoms, or more rarely inflammatory arthritis or heart problems.
  • A small proportion of patients with Lyme disease go on to develop chronic, non-specific symptoms, the cause of which is not clear. Possible reasons suggested are persistence of the infectious organism, another infection, immune system over-activity, or from post-infectious damage to the body.


Testing and diagnosis

  • Diagnosis can be tricky due to similarity of symptoms with other conditions. Diagnosis is usually based on clinical symptoms and a history of recent exposure to infected ticks. GPs are advised to treat early Lyme with antibiotics, typically when a rash is present, without the need for a blood test.
  • If laboratory tests are needed to confirm Lyme disease infection, these can be requested by GPs. The NHS uses validated tests that work by detecting antibodies produced in response to the pathogen. Antibodies are usually present from about six weeks to several months after infection. They persist if the infection is active but will drop off in time after treatment.
  • False negative results may occur when antibody levels aren’t yet high enough to register, e.g. in early Lyme, and false positive results may also occur due to non-specific reactions.
  • Private laboratories in the UK and abroad sometimes use tests for which there is no published evidence of their accuracy and reliability. In the UK, tests used by PHE/NHS are validated and are the same tests used in public laboratories worldwide.



  • Early Lyme disease is treated with a short course of oral antibiotics. If appropriate antibiotics are given early enough then most patients will completely recover.
  • More complex late Lyme and neurological Lyme may require longer oral antibiotic courses or even intravenous antibiotics.
  • If Lyme disease has remained undiagnosed for months or even years, then antibiotic treatments may not remove all symptoms. In such cases, there is no consistent evidence that long term treatment with antibiotics is of any benefit to the patient.



  • In the UK, Lyme disease case numbers are based on laboratory-confirmed cases only. Cases that are diagnosed on the basis of their clinical symptoms are not included.
  • For England and Wales, PHE reported 872 cases of laboratory-confirmed Lyme borreliosis in 2015 and 730 cases in 2014.
  • The Centers for Disease Control and Prevention receives reports of approximately 30,000 cases of Lyme disease in the US each year and they estimate that around 300,000 people nationwide contract the disease annually.


Chronic Lyme disease

  • ‘Chronic Lyme disease’ is a term sometimes used to describe the condition in patients with persisting symptoms which they believe are due to Lyme disease.
  • Such a diagnosis is controversial as the disease process that is causing symptoms in these patients has not been established and many such patients do not have any laboratory-confirmed evidence of the disease.


Sources / further information

NHS Choices Lyme disease

PHE Tick bite risks and prevention of Lyme disease: factsheet

PHE Lyme Disease Signs and Symptoms factsheet

PHE GP Referral Pathway

CDC Lyme disease

Lyme Disease Action FAQs



This is a Factsheet issued by the Science Media Centre to provide background information on science topics relevant to breaking news stories. This is not intended as the ‘last word’ on a subject, but rather a summary of the basics and a pointer towards sources of more detailed information. These can be read as supplements to our Roundups and/or briefings.



Updated 01/08/2016

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