Is Lyme Disease Contagious?

While the exact numbers are difficult to nail down, data from the Centers for Disease Control and Prevention (CDC) indicates that as many as 476,000 cases of Lyme disease may occur annually across the U.S. 

The bacteria responsible for Lyme disease is carried by infected blacklegged ticks and can be passed to humans through their bite. Early warning signs of infection often include fever, aches in the joints and muscles, chills, fatigue, headache, or swollen lymph nodes. Most often, these symptoms emerge within three to 30 days following an infected tick bite. On average, after about a week, a warm, ring-shaped rash may begin to emerge and grow outward around the site of the bite — however, not everyone will experience this hallmark "bull's-eye" rash. Over time, infection can lead to facial paralysis, arthritis, or brain and spinal cord inflammation if a person goes without treatment.

Thankfully, not all blacklegged ticks carry Lyme disease. Additionally, infection risk is also dependent upon how long the tick remains attached to its host. Some experts say it takes a full 24 hours before bacterial transfer can occur, while others say a tick would need to be munching on us for as many as 36 to 48 hours before we were at risk (via NPR).

If someone you know has contracted Lyme disease, you may be wondering if it's possible for them to transmit it to you, or vice versa. However, there is no current research that conclusively shows humans can spread Lyme disease to one another in the same way we might spread other types of illnesses like a cold, reports Healthline.

Although an infected person's urine, saliva, or breast milk can harbor the bacteria, it has not been proven that Lyme disease can be contracted by another person through direct contact with contaminated body fluids. The same is true sexual intercourse, kissing, or skin-to-skin contact, according to the CDC. There is also no strong evidence suggesting that it can travel via food, water, or air either.

Because the bacteria that causes Lyme disease makes its way into the bloodstream, you might be concerned whether or not blood transfusions pose any infection risk. Although the bacteria can survive in donated blood samples, health experts state that no transfusion-related cases of Lyme disease infection have been detected. Even so, blood donation is advised against for those actively being treated for the condition.

The only manner in which Lyme disease is considered contagious is in rare cases of vertical transmission — meaning a pregnant person with Lyme disease may be able to pass the infection along to the fetus through contamination of the placenta, according to the CDC. However, antibiotic treatment negates any increased risk of birth defects.

Early intervention with antibiotic treatment will cure Lyme disease in nearly 100% of cases, according to Penn Medicine. Antibiotics need to be taken for approximately 10 to 14 days in order to complete treatment. However, people with more severe cases of infection may need to be treated for a longer period of time. Treatment drugs include amoxicillin, azithromycin, cefuroxime, and doxycycline.

In cases of post-Lyme disease syndrome, an individual may continue to experience debilitating symptoms even after treatment has been completed. Most often, however, experts report that people who receive early treatment for Lyme disease tend to feel back to normal within one years' time.