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In the ancient and medieval periods, dysentery killed about ? of all babies before they reach 12 months of age. The disease was transferred through contaminated drinking water, because there was no way to adequately dispose of sewage, which contaminated the water.
Thyroid conditions cause a higher risk of fibromyalgia and chronic fatigue syndrome.
Women are two-thirds more likely than men to develop irritable bowel syndrome. This may be attributable to hormonal changes related to their menstrual cycles.
Over time, chronic hepatitis B virus and hepatitis C virus infections can progress to advanced liver disease, liver failure, and hepatocellular carcinoma. Unlike other forms, more than 80% of hepatitis C infections become chronic and lead to liver disease. When combined with hepatitis B, hepatitis C now accounts for 75% percent of all cases of liver disease around the world. Liver failure caused by hepatitis C is now leading cause of liver transplants in the United States.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.
![Areas of differing productivity and diversity in a wetland. (a) Typha dominates core habitats, while](https://biology-forums.com/gallery/47/medium_33_17_02_12_5_45_22_2002220.jpeg)
![Spinal cord—levels of injury; A, areas of sensory function (dermatomes); B, areas of motor function.](https://biology-forums.com/gallery/47/medium_18099_25_10_12_10_55_44.jpeg)