Sexual intercourse can act as a mechanism for spreading infectious diseases from one host to another. These include gonorrhea, chlamydia, both caused by bacterial infection, and genital warts, herpes, hepatitis, and best known for AIDS, which are result of viral infection.
Acquired Immunodeficiency Syndrome (AIDS) is caused by a group of retroviruses known as HIV (human immunodeficiency viruses) that infect specific blood cells. It is usually transmitted through body secretions, such as semen or blood. When HIV enters a new host it attaches to cells with specific receptors (CD4 receptors). Once inside the host cell, the virus which carries its genetic information in the form of RNA not DNA, uses a special enzyme (reverse transcriptase) to translate its RNA code into DNA code and inserts it into the DNA code of the host cell. The new DNA then makes the host cell produce more viral RNA. The viral RNA causes the cell to make a special protein which coats the RNA allowing formation of new HIV viruses which bud from the infected cell and proceed to infect other cells, causing the same process to happen in them too. In the early stages of the disease the infected person usually doesn't have any symptoms, and even the few people that do have some reaction (fever, itchy rash, chills aches, swollen lymph nodes) rapidly become asymptomatic. If tested for the disease at this stage the person would be negative as the test tests for the presence of antibodies and these antibodies have not yet started to be made. However, the person already has a high enough viral load to be infectious should they engage in risky sexual behavior. After months to years of being asymtomatic, a non treated individual will start to show a decrease in the number of helper T lymphocytes (the primary host cells of HIV). At this point their T-cell counts (usually above 500 per mm2) has dropped to between 200 and 500. They will start to show swelling in the lymph nodes of the groin, neck and/or armpits, severe fatigue, recurrent fevers and persistent diarrhea. As the disease progresses the person becomes more and more susceptible to non-life-threatening infections such as thrush and herpes simplex due to the damage being done to their immune system by the HIV. In the final stage of the disease ("Full-blown AIDS"), the T-lymphocyte count has dropped to 200 or less and the lymph nodes start to degenerate. The person, weakened by constant coughing and diarrhea will eventually die as a result of the effects of some other opportunistic infection, such as pneumonia, tuberculosis, encephalitis or a form of cancer, commonly Kaposi's sarcoma. There is not yet a cure for AIDS, but a number of treatments have been developed with have markedly improved the life quality and length for many HIV patients. The most common therapy involves two drugs that inhibit reverse transcriptase and another one that inhibits the protease needed for manufacture of the virus' protein capsule. The sooner treatment is given after infection, the more effective it is and once started, medications must be taken regularly, or else the effects are lost.
Hepatitis: There are several types of this disease. Hepatitus A is usually caused by drinking sewage-contaminated water, although it can be transmitted through oral/anal sex. Hepatitis C is usually contracted by contact with infected blood, usually via transfusions. Hepatitis B can also be transmitted by contact with infected blood, however it is largely spread by sexual contact. In many the disease is asymptomatic, but in about half symptoms such as fatigue, headache, fever, nausea and even jaundice. In severe infections it can cause liver failure, which requires a liver transplant to prevent death. There is now a vaccine against this disease and this vaccine is often now routinely given to children as it does not appear to have any major side effects.
Genital herpes: There are two main types of herpes virus. Herpes simplex 1 is often associated with cold sores, while herpes simplex 2 usually causes genital herpes. Today genital herpes is probably one of the more common STDs. When first contracted the disease can be asymptomatic until blisters erupt 2-20 days after infection. These blisters eventually rupture leaving painful sores that can be very slow to heal. Once they do heal the person can then become asymptomatic for long periods before the disease erupts once again. Newborn babies coming in contact with the virus can become very ill, and infection may result in blindness, braindamage or even death. Thus it is important that infected mothers give birth via C-section.
Genital warts: This disease is caused by the human papillovirus (HPV) and is usually spread via sexual contact. It is probably the most common viral STD in most Western Societies. Carriers may be completely asymptomatic, or may occasionally develop warts in the genital region. More serious than the warts however, is the emerging evidence that HPV is associated with 90-95% of all cases of cervical cancer. There is currently no cure or vaccine for this disease, although the warts can be removed surgically in a number of different ways.
Gonorrhea: Caused by a bacterium this disease causes painful urination and the discharge of a thick, greenish-yellow discharge from the penis of most recently infected males. It is also possible for the anus, throat and tonsils to be infected by this bacteria when infected partners engage in oral or anal sex. Other parts of the body may also be infected (e.g. eyes can become infected if a person touches infected genitals or secretions and then brings their hands to their eyes). In females the disease usually affects the urethra or the cervix and oviducts, giving rise to Pelvic Inflammatory Disease (PID). As the oviducts heal from this infection they may become partially or totally blocked by scar tissue, resulting in sterility and an increased chance of ectopic pregnancies. Unfortunately, unlike males many (60-80%) females are asymptomatic until the PID becomes severe.
Chlamydia: Another bacteria infection, this is probably the single most abundant STD. In men symptoms include painful urinatuion and mucus discharge. In females the symptoms are usually vaginal discharge or a urinary tract infection. If not properly treated this disease can result in PID and the ensuing problems of sterility and ectopic pregnancy. Many people suffering from gonorrhea also suffer from chlamydia.
All people should bear in mind that the transmissions of STDs are usually the result of having multiple sex partners. Although the society is always promoting safe sex, using condom during sexual intercourse, it cannot 100% save people from being infected. This is because the plastic latex from which condoms are made contains pores between molecules. Some viruses are much smaller than sperms and pores, and thus go through the pores on the condom to effect infection. Therefore, using condom can only lessen the risk of contracting the diseases, but cannot totally prevent them. The only way to safeguard oneself from being infected is having a lifelong commitment to one sex partner. This commitment has more meaning than fidelity alone.