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Lyme disease basics
A bacterial infection spread by blacklegged ticks, and the most common tick-borne illness in the US.
Lyme disease is a bacterial infection spread by the bite of an infected tick. It is well established as the most common tick-borne illness in the United States, and it is also recognised across the UK and much of Europe. Its status is different in Australia, which is covered in its own section below rather than assumed to apply everywhere.
The basics
- Cause: Borrelia bacteria, carried by blacklegged (deer) ticks
- Spread: only by tick bite. Not from person to person, or from pets
- Treatment: antibiotics, usually two to three weeks
- Outlook: most people recover fully when treated early
Early signs
- An expanding rash at the bite site, sometimes clearing in the centre as it grows
- Fever, chills and headache
- Aching muscles and joints
- Unusual tiredness
Not everyone gets the rash. Flu-like symptoms in tick season, with no cough or sore throat, are worth mentioning to a doctor.
The rash, where it appears, is usually the clearest early sign, but its absence does not rule anything out. Flu-like symptoms with no obvious respiratory cause, appearing after time outdoors in tick season, are worth flagging to a doctor even without a rash.
If it goes untreated
The infection can spread to the joints, the nervous system and the heart over weeks to months, causing swollen joints, facial weakness, or an irregular heartbeat. It is still treatable at that stage, but recovery takes longer.
Lyme disease is not contagious. You cannot catch it from another person or from your dog.
Regional picture
United States & Canada
Lyme disease is well established and widely tracked by the CDC, with blacklegged ticks as the main carrier. It is the tick-borne illness most people mean when they say "Lyme".
Australia
Locally-acquired Lyme disease is not officially recognised in Australia. Health authorities have not confirmed that the Borrelia bacteria responsible for Lyme disease are transmitted by ticks native to Australia, and this remains a genuinely debated position rather than a settled one in either direction. Cases diagnosed in Australia are generally linked to travel or tick exposure overseas. Australia's principal tick health concerns are different from the Lyme picture described above: the paralysis tick, which can cause a distinct illness with muscle weakness and unsteady movement, and tick-induced mammalian meat (alpha-gal) allergy, where a bite triggers a new allergy to red meat. Anyone in Australia with ongoing symptoms after a tick bite should be assessed against these locally relevant conditions rather than assuming the US Lyme pattern applies.
UK & Europe
Lyme disease occurs across the UK and mainland Europe, carried by regional tick species, and is tracked by the NHS and ECDC. The early signs and treatment approach are broadly similar to the US picture.
Testing and diagnosis
Blood tests for Lyme disease look for the body’s immune response to the bacteria, which takes time to develop; testing too soon after a bite can miss an infection that is genuinely present. Because of this, a doctor may begin treatment based on a recent bite, the right kind of tick, and a matching rash or symptom pattern, without waiting on a test result. This is a normal and accepted part of how the infection is managed, not a shortcut.
Prevention and what TickSentry can help with
There is no way to know from the bite alone whether a tick was infected, which is why prevention and prompt removal matter more than trying to assess risk after the fact. Checking yourself, family members, and pets after time outdoors, and removing any attached tick as soon as you find it, remains the most effective thing you can do. See how long before a tick transmits disease for why attachment time matters so much, and tick bite symptoms for what a bite typically looks like as it develops.
TickSentry cannot tell you whether a tick was carrying Lyme disease or any other infection, and it does not diagnose anything. What it can do is help you identify the tick you found with the tick identifier, see what has been reported nearby on the tick sightings map, and work through your own situation with the symptom and bite checker. If anything you notice matches the urgent signs above, see when to see a doctor without delay.