Coxsackie myocarditis is inflammation and weakness of the heart muscle caused by a viral infection (Coxsackie virus) that reaches the heart. Myocarditis can damage the heart muscle causing it to become thick and swollen. The heart muscle may be directly damaged by the virus or the bacteria that infect it. The body’s immune response can also damage the heart muscle (called the myocardium) in the process of fighting the infection. This can lead to symptoms of heart failure. Symptoms may include: anxiousness, failure to thrive or poor weight gain, feeding difficulties, fever and other symptoms of infection, listlessness, low urine output (a sign of decreasing kidney function), pale, cool hands and feet (a sign of poor circulation), rapid breathing, and rapid heart rate. Myocarditis may also occur during or after other viral or bacterial infections such as the influenza (flu) virus, adenovirus, polio, rubella, Lyme disease, and others. Myocarditis is rare in young children. It is slightly more common in older children and adults. It is often worse in newborns and young infants than in children over age 2. There is no cure for myocarditis. The heart muscle inflammation will often go away on its own.