Lyme disease is not contagious in the usual sense. You cannot catch it from touching, kissing, or being near someone who has it. The only established way humans get Lyme disease is through the bite of an infected blacklegged tick (also called a deer tick), which must remain attached long enough to transfer the bacteria into your skin.
Why Casual Contact Doesn’t Spread It
The bacterium that causes Lyme disease, a corkscrew-shaped organism called a spirochete, depends on a very specific biological process to infect a new host. Inside the tick’s gut, the bacteria need time to activate and migrate to the tick’s salivary glands before they can enter your bloodstream. This process typically takes 36 to 48 hours of attachment. Without that tick-mediated step, the bacteria don’t have a viable route into a new person’s body.
The CDC states plainly that there is no credible scientific evidence Lyme disease spreads through touching, kissing, or sexual contact. Animal studies have tested sexual transmission directly and found it doesn’t occur, and the biology of the spirochete isn’t compatible with that route of exposure.
The Sexual Transmission Debate
A small number of researchers have raised the question of whether Lyme bacteria could be present in genital fluids. One study cultured genital secretions from 13 patients diagnosed with Lyme disease and detected spirochete DNA in 11 of them. An earlier study in 2001 reported finding spirochetes in the semen and vaginal swabs of some Lyme patients and their partners.
These findings sound alarming, but they haven’t led to any confirmed cases of sexual transmission. Detecting bacterial DNA in a fluid is not the same as proving that fluid can infect another person. A comprehensive review by the UK’s National Institute for Health and Care Excellence searched for any studies reporting actual transmission through sexual contact and found none. No observational studies, no documented cases, no epidemiological patterns suggesting it happens. Major public health agencies continue to classify sexual transmission as unsupported.
Pregnancy and Breastfeeding
Vertical transmission, where a pregnant person passes the infection to their baby, is a more nuanced question. Published case reports describe 19 instances where the Lyme bacterium was identified in fetal or infant tissue after miscarriage, stillbirth, or neonatal death. An additional 15 cases of suspected congenital infection have been reported, including two infants with Lyme-specific antibodies in their spinal fluid. The bacterium has also been found in placentas from both treated and untreated pregnancies.
Treatment makes a significant difference. One review found that adverse pregnancy outcomes occurred in over 50% of untreated cases but dropped to about 11% with appropriate antibiotic treatment. Another analysis showed adverse outcomes in 74% of untreated pregnancies, 29% with oral antibiotics, and 12% with intravenous antibiotics. These numbers underscore that prompt treatment during pregnancy matters, not that the infection is casually contagious.
Breastfeeding appears to be safe. The CDC reports no documented cases of Lyme disease spreading to infants through breast milk, and mothers being treated with antibiotics can generally continue breastfeeding with guidance on which antibiotics are compatible.
Can You Catch It From a Pet?
Your dog or cat cannot give you Lyme disease through direct contact, licking, or sharing space. According to Cornell University’s veterinary program, humans don’t get Lyme from dogs. Both you and your pet catch it the same way: from an infected tick bite. However, pets that spend time outdoors can carry unattached ticks into your home on their fur, and those ticks can then bite you. The risk isn’t the pet itself but the ticks hitchhiking on it. Regular tick prevention for pets reduces this indirect risk.
Blood Donation and Transfusion
No confirmed case of Lyme disease transmission through blood transfusion has been documented, but the possibility hasn’t been entirely ruled out either. Some American blood collection facilities defer potential donors who have a confirmed Lyme diagnosis or who report a recent tick bite. The deferral period varies by facility. Routine blood screening doesn’t include testing for the Lyme bacterium, which means the system relies on donors self-reporting their history rather than catching infections in the lab. This is a gap that some researchers have flagged, particularly in regions where Lyme is common, but so far the theoretical risk hasn’t translated into real-world cases.
What Actually Puts You at Risk
Since tick bites are the only proven route, your risk comes down to tick exposure. Blacklegged ticks live in wooded, brushy, and grassy areas, particularly in the northeastern United States, the upper Midwest, and parts of the Pacific coast. Peak transmission happens in late spring and summer when nymphal ticks (the juvenile stage, roughly the size of a poppy seed) are most active. These tiny nymphs cause the majority of human infections because they’re hard to spot and easy to miss during a body check.
You can share a bed, a home, and a life with someone who has Lyme disease without any risk of catching it from them. The only thing you share is the environment, and if one person in a household gets Lyme, it’s worth checking whether others have also been exposed to ticks in the same area.