Infectious diseases become a major problem to kill more people worldwide. The diseases caused by germs and which may infect any part of the body are called infectious diseases. They are caused by pathogenic microorganisms such as bacteria, virus, parasites and fungi. Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites and can spread between individuals. STDs (or STIs) are infections that can mostly be passed on to another person during sex, be it anal, oral or vaginal sex. Most STDs affect both men and women, but in many cases the health problems they cause can be more severe for women. If a pregnant woman has an STD, it can cause serious health problems for the baby. If untreated, STIs can increase your risk of acquiring another STI such as HIV.