Lyme Disease

Sometimes referred to as: Lyme borreliosis

Interview between:

  • Andrew Cunningham, MD

  • Jimmy Chen, MD

Lyme disease is a bacterial spirochetal infection, caused by the Borellia species, most often Borrelia burgdorferi. The bacteria is transmitted to humans by a bite from an infected black legged tick (also called “deer tick”). It can cause acute symptoms, including a rash, flu-like symptoms, and tiredness. It can also develop into a more chronic disease affecting the nervous system, heart, and joints.

Cases Per Year (US)

30,000 cases of Lyme reported annually, 300,000 cases per year is more likely

General Frequency

Of all reportable diseases, Lyme was the sixth most common in 2016 and it is thought to account for 63% of all vector-transmitted diseases (meaning those transmitted through ticks, mosquitos, etc.).


Risk of Lyme disease is correlated with exposure to ticks carrying the bacteria. This risk is especially high in certain geographical areas, and more specifically, when participating in outdoor activities in these areas, during spring and early summer.



Are we seeing more or less Lyme disease than previously and why?

Cases of Lyme have risen steadily over the past 25 years, having doubled between 2004 and 2016 (though this also takes into account cases that were probable but not confirmed). There are several possible reasons for this. 

One is that climate change has caused the tick vector, the Ixodes tick, to expand its geographic range south and west from the Northeastern states. 

Another is that the animals that ticks typically feed on, such as the white-footed mouse in the Northeast, have also increased their geographic range. 

Lastly, there’s been an increase in travel to regions where Lyme is prevalent. 

What are the areas of most concern in the United States?

The majority of cases (96%) are found in 14 states, mostly in the Northeast and upper Midwest, though there are cases reported in most states. 

What time of year do we worry most about with Lyme transmission?

Lyme transmission increases during the summer months due to the life cycle of the ticks that carry it. Ticks go through three stages during their life cycle including larva, nymph, and adult. The nymphs are the most likely to transmit Lyme (though adults also transmit), and nymphs are most active from late spring to early summer. 

What does a tick bite look like? Will there always be a tick attached? 

While the classic early finding in Lyme is the “bull’s eye” rash (referring to the area of central clearing and red rings, making it look like a target), it’s very important to recognise that not all patients develop (or recall developing) this rash, and it doesn’t always have this bull’s eye appearance when they do. Additionally, ticks can be so small–sometimes the size of a poppyseed–that people sometimes don’t notice the tick at all while it’s attached.

Is Lyme disease contagious among humans, pets, etc., or can it only be contracted from ticks?

There is no evidence that Lyme disease is transmitted from person-to-person through sharing of utensils, sexual contact, or breast feeding. Women who have been treated for Lyme disease prior to becoming pregnant have no cause for concern in terms of transmission to the fetus. Women who contract the disease while pregnant should be treated appropriately, though it’s important that the selected medication is safe during pregnancy. 

Having pets may increase the risk of exposure to ticks (but you can’t get Lyme directly from your pet), and pets are also at risk for contracting the disease from tick bites. 

There is evidence that Lyme disease may live in the blood or tissues, and while there are no recorded cases of transmission through a blood transfusion, people who are actively being treated for the disease should avoid donating blood.


Symptoms and Causes







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Andrew Cunningham, MD and Jimmy Chen, MD are both members of the Galileo Clinical Team. Connect with one of our physicians about Lyme Disease or any of the many other conditions we treat.

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