How Many Ticks Carry Disease? Infection Rates Explained
In short: Most ticks are not infected. According to the Robert Koch Institute, even in TBE risk areas only 0.1 to 5 per cent of ticks carry the TBE virus on average; Borrelia are more common, in up to 30 per cent. Symptoms of disease are to be expected after 0.3 to 1.4 per cent of tick bites, according to the RKI.
The figures at a glance
| Question | Answer according to the RKI |
|---|---|
| Share of ticks carrying TBE virus in risk areas | 0.1 to 5 % on average, varying strongly locally |
| Share of ticks carrying Borrelia | up to 30 %, varying strongly locally |
| Borrelia infection detected after a bite | in 2.6 to 5.6 % of people |
| Symptoms of disease after a bite | after 0.3 to 1.4 % of tick bites |
TBE virus in ticks
The RKI writes that even in Germany's TBE risk areas only a few ticks are infected and that virus levels can vary very strongly over short distances — 0.1 to 5 per cent on average. Regional studies show how different that looks in detail:
- Rhine-Main area (Hesse), 2009–2010: 0 to 0.2 % in risk areas (3 of 3,947 ticks examined), 0 % outside them
- Lower Bavaria and Upper Palatinate, 2010: 0.26 % on average, up to 2.86 % at the worst-affected individual sites
- Odenwald, crowdsourcing study with 17,893 ticks: 0.04 % on average, up to 0.12 % depending on the district
Worth understanding: a TBE risk area describes where the virus occurs in the tick population — not how many ticks there are infected. According to the RKI, no risk of disease for a single bite can be derived from it, especially as many TBE infections cause no or only mild symptoms. A TBE vaccine exists; whether it makes sense for you is a question for your doctor.
Borrelia in ticks
For the pathogens behind Lyme disease, rates are considerably higher. The RKI names up to 30 per cent but stresses that occurrence varies very strongly locally — it can differ between two patches of woodland. We have therefore not adopted the fixed values per German state that circulate in advice articles: most can't be traced to any single study.
From an infected tick to illness
An infected tick doesn't mean infection, and infection doesn't mean illness. The RKI cites studies from Germany and Switzerland: after a tick bite, a Borrelia infection — detectable by antibodies in the blood — was found in 2.6 to 5.6 per cent of people. Only a small share of them fall ill. Overall, symptoms are to be expected after 0.3 to 1.4 per cent of tick bites.
For Borrelia, time matters too: the pathogens sit in the tick's gut, and the risk of infection rises after more than 12 hours of feeding, according to the RKI. Removing the tick early keeps the risk very low. More in "How long does a tick feed?"; Germany's notification figures are in "TBE and Lyme disease case numbers in Germany".
Why the exact figure matters less
Even at the highest values, most ticks are not infected — but you can't tell by looking whether a tick is one of the few. That's why it pays to treat every tick the same: remove it quickly and properly, and watch the spot. The method is in "How to remove a tick properly", what to watch for afterwards in "Tick bite — what to do now".
Find it first, then remove it: TickSpot shows ticks in seconds — free, no sign-up.
Start the tick checkFrequently asked questions
How many ticks carry the TBE virus?
Only a few, even in risk areas. According to the Robert Koch Institute, on average 0.1 to 5 per cent of ticks there carry TBE virus, with very strong local variation. Regional studies from Hesse and Bavaria found values between 0 and just under 3 per cent.
How many ticks are infected with Borrelia?
Far more than with TBE virus. The RKI writes that the occurrence of Borrelia in ticks varies very strongly locally and can be as high as 30 per cent.
How likely is Lyme disease after a tick bite?
According to studies from Germany and Switzerland cited by the RKI, a Borrelia infection was detected in 2.6 to 5.6 per cent of people after a tick bite. Overall, symptoms of disease are to be expected after 0.3 to 1.4 per cent of tick bites.
Can you tell by looking whether a tick is infected?
No. It can't be seen from the outside. That's why the same applies to every tick: remove it properly as soon as possible. For Borrelia, the risk of infection rises after more than 12 hours of feeding, according to the RKI.
Sources
- Robert Koch Institute: Tick FAQ (TBE virus and Borrelia in ticks, infection and disease rates after a bite — in German)
- Robert Koch Institute: Lyme borreliosis FAQ (feeding time and infection risk — in German)
- Rhine-Main study: PubMed 23415373
- Lower Bavaria/Upper Palatinate study: PubMed 31983627
- Odenwald study: Parasites & Vectors 13, 250 (2020)
Note: This article is for general orientation and does not replace medical advice. After a tick bite with symptoms or if unsure, seek medical advice.