Summer can also bring ailments that originate in disease-bearing pests. One that can endanger your heart is Lyme disease, which is transmitted by the bacterium Borrelia burgdorferi through the bite of an infected blacklegged tick — known as the deer tick, because its primary host is the white tail deer.

Every year, state health departments in the United States report about 30,000 cases of Lyme disease to the Centers for Disease Control and Prevention (CDC). But the agency believes the true number of cases could be 10 times that many.

Lyme disease causes fever, headache, body aches, stiff neck, and fatigue. Fortunately, antibiotics can cure most cases, and the earlier the treatment, the better the results.

Although Lyme disease rarely causes death, a rare complication known as “Lyme carditis,” an inflammatory disease that strikes the heart, presents special danger. Symptoms of Lyme carditis include palpitations, chest pain, dizziness, and passing out.

Lyme carditis can also cause inflammation of the pericardium, the membrane that holds the heart.

One symptom of this inflammation is sharp chest pain that increases with deep breaths or lying down. Over time, the pericardium can thicken and stick to the heart muscle, impeding heart function and causing swelling of the legs, feet, and abdomen, as well as other symptoms like lightheadedness, shortness of breath, and exercise intolerance.

Most people with Lyme carditis also develop a problem in their heart’s electrical system, typically some degree of heart block, which can result in a very slow heart rate (called bradycardia) that puts them at risk for passing out, dizziness, chest pain, and shortness of breath.

In most cases, early treatment with intravenous antibiotics can resolve Lyme carditis, although sometimes a temporary pacemaker may need to be implanted.