A UTI is an infection in the urinary tract. Infections are caused by microbes—organisms too small to be seen without a microscope. Bacteria are the most common cause of UTIs. Normally, bacteria that enter the urinary tract are quickly removed by the body before they cause symptoms. But sometimes bacteria overcome the body’s natural defenses and cause infection.

What are some of the myths – and facts – about vaccination?

The last stage of HIV (human immunodeficiency virus) infection is AIDS (acquired immune deficiency syndrome). Once you get an HIV infection, you have it for life, but it does not progress to AIDS in all people. With antiretroviral therapy treatment (ART) many people can live a normal life expectancy with HIV infection.