Health Library
The Health Library is a collection of health and wellness resources created for learning and accessibility. Select a topic below for related health information or search for a topic in the search bar for more information on other medical conditions.
Disease Stages
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Sleep apnea occurs when you regularly stop breathing for 10 seconds or longer during sleep. It can be mild, moderate, or severe, based on the number of times an hour that you stop breathing (apnea) or that airflow to your lungs is reduced (hypopnea). This is called the apnea-hypopnea index (AHI)...
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Syphilis is described in terms of its four stages: primary, secondary, latent (hidden), and tertiary (late). Primary stage During the primary stage, a sore ( chancre) that is usually painless develops at the site where the bacteria entered the body. This commonly occurs within 3 weeks of exposure but can...
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The American College of Cardiology and the American Heart Association have devised a classification system for heart failure. It categorizes heart failure based on how the disease progresses in most people. Under this system, heart failure is...
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Lyme disease can go through several stages. It may cause different symptoms, depending on how long you have been infected and where in your body the infection has spread. Stage 1: Early localized Lyme disease (1 to 4 weeks) Early localized Lyme disease develops days to weeks after you become infected. You may have...