context: People with another form of hepatitis, HIV, hemophilia, kidney disease, and diabetes have a higher rate of infection with the hepatitis C virus ( HCV) than the general population. Some conditions share a common transmission route with HCV, such as other viruses, hepatitis B, and HIV. In addition, HCV can be acquired as the result of a blood transfusion or organ transplant given to treat a disease like hemophilia or kidney disease. In some cases, the increased rate of HCV is unexplained. A recent study suggested that diabetics, too, have a higher prevalence of HCV infection than the general population, though researchers remain unsure why. The course of hepatitis C -- and its treatment -- may change when it co-exists with other medical conditions. Likewise, the disease course and treatment plan of the concurrent medical condition can be affected. Although research is ongoing, some of the current information on HCV and co-existing conditions appears below. It is not infrequent for people with HCV to be additionally infected with another hepatitis virus. It has been noted by some researchers that liver failure and even death can occur in people with chronic hepatitis C who become infected with the hepatitis A virus ( HAV). HCV and HBV have shared modes of transmission. Approximately 10% of people with HCV are thought to be co-infected with hepatitis B. Some studies have found that people infected with both HCV and HBV have a very aggressive course of disease and are at increased risk of developing cirrhosis and liver failure. Therefore, everyone with HCV who has not been exposed to HAV or HBV is urged to obtain the vaccinations against these other hepatitis viruses. HCV has also been linked to autoimmune hepatitis. Autoimmune hepatitis is a condition in which a person's immune system harms the cells of the liver, mistaking them for foreign bodies. Autoimmune hepatitis is associated with other autoimmune disorders, among them diabetes. Researchers are examining these associations to try to understand why people with diabetes, on average, also exhibit a high rate of HCV infection. Co-infection with hepatitis C and HIV occurs due to a common mode of transmission. Although there currently are no estimates on the prevalence, studies estimate that up to 25% of people are co-infected. People with both HCV and HIV tend to have higher viral counts of HCV in their blood and livers compared with people infected only with hepatitis C. HIV appears to accelerate HCV disease progression approximately four times faster than the disease progression in HCV-infected individuals who do not have HIV. Approximately 25% to 50% of patients co-infected with HIV and HCV are thought to progress to cirrhosis, compared to approximately 20% of individuals infected with HCV alone. Conversely, HCV appears to have no effect on the progression of HIV to AIDS. HCV-related mortality is currently more common than HIV-related mortality in co-infected patients. Co-infection appears to increase the chance that HCV will be sexually transmitted. It also appears to increase the chance that a mother will infect her unborn child with the virus. This may be due, in part, to the high viral count in this subset of patients. Treatment for HCV infection should not be withheld because a patient has concurrent HIV infection. Rapid advances in hepatitis C drugs have led to the development of highly effective direct-acting antivirals. These recently FDA-approved drugs are used with or without ribavirin and need to be chosen with careful attention to the complex drug interactions that occur with the antiretroviral medications used to treat HIV. Before routine and effective hepatitis C screening of the blood supply was established in 1992, many hemophiliacs received HCV-infected blood products. Approximately 70% to 80% of hemophiliacs carry HCV, though the percentage is declining year after year as fewer new cases develop. Although some people with hemophilia were infected with HCV multiple times, from multiple blood products, their disease progression does not appear to be any more severe than the disease progression in HCV-infected individuals without hemophilia. In general, HCV-infected hemophiliacs whose condition is not further complicated with HIV infection are treated with newer direct-acting antivirals with or without ribavirin. They have high cure rates, fewer side effects, and treatment can take as little as 8 weeks. Approximately 10% to 49% of kidney transplant recipients have antibodies for hepatitis C in their blood. Chronic HCV infection in these individuals appears to carry twice the risk of a serious post-transplant infection, compared to kidney transplant patients who do not test positive for HCV antibodies. However, there is no data indicating that HCV-infected kidney transplant recipients have a higher rate of transplant rejection or death. Pegylated interferon-based treatment is not recommended for HCV-infected kidney transplant recipients, because the treatment puts them at a high risk for transplant rejection. Sometimes these patients are treated before receiving a transplant. Rapid advancements in hepatitis C drugs has provided interferon-free regimens that are highly effective and well-tolerated. As in the general population, co-infection with both hepatitis C and hepatitis B appears to hasten disease progression in kidney transplant patients, increasing their risk of liver failure and death. Hemodialysis patients have become infected with hepatitis C through blood transfusions, organ transplants, and, possibly, though hemodialysis equipment. About 8% of hemodialysis patients in the U. S. have HCV. Chronic HCV infection appears to accelerate the progression of kidney disease in hemodialysis patients. With regard to the progression to liver disease, again, these patients appear to be more affected by co-infection with both HBV and HCV than HCV alone. Although the association is poorly understood, there appears to be a connection between hepatitis C and diabetes. One study reported that people with diabetes had four-times the rate of HCV infection than those without diabetes. Another study reported that of 100 patients with cirrhosis, 34 had HCV infection. Of those, 17 (50%) had concurrent diabetes. Of the 66 HCV-free patients, only six (9%) had concurrent diabetes. Additional studies substantiate that diabetes is more prevalent in people with HCV infection than in people with other liver diseases -- even when a family medical history and other risk factors for diabetes are considered.