There are two broad categories of infection: bacterial and viral. Bacteria (singular bacterium) are one-celled micro-organisms that serve various purposes. Most are harmless, some are beneficial, and others cause disease in humans. Viruses are smaller and attack the cells of living organisms, using them to replicate. For example, the humane immunodeficiency virus (HIV) attacks those cells in a body that help fight disease, destroying them and leaving the infected person vulnerable to opportunistic diseases like pneumonia, tuberculosis, and some forms of cancer in a condition known as AIDS, or acquired immune deficiency syndrome. A few other examples of bacterial infections include strep throat, pneumonia, sinusitis, and salmonella. Common viral infections include the common cold, smallpox, measles, and influenza (the flu).
When it comes to prevention, treatment, and cure, there is a big difference between bacterial and viral infections. We've all heard that there is no cure for the common cold, and that's true of most viral infections. At best, they can be treated. Once infected by a virus, that virus remains in a person's body – for life. However, after the initial infection subsides, the existence of that virus helps the body fight off future infections and the person is said to have an immunity against the disease. Hepatitis A is a good example of this. Once a person is infected, they may become ill for a short period of time during which the doctor can prescribe treatments to help the body fight the disease, but cannot eradicate it. After the infection subsides, the hepatitis A virus remains in the body, helping the body fight off future infection. Because of its presence, a person infected with this virus can never give blood, but is unlikely to contract this disease again. This is why people usually only get mumps, chicken pox or measles only once. The good news is that vaccinations can be developed that leverage this natural immunity. When you receive a vaccination, you are actually being injected with a dormant strain of the virus. This "teaches" your body how to fight the virus.
As for STDs, sexually transmitted diseases, HIV (mentioned earlier), hepatitis, and herpes are all viral. As such, these infections cannot be cured, only treated, although treatment options have come along way for those infected. Vaccinations are in development for HIV, herpes, and hepatitis C. A Vaccine exists for hepatitis A and B. It is important to remember that once you are infected with one of these viruses, you are infected for life. There is no cure, only treatment.
Bacterial infections, on the other hand, can be cured using a simple antibiotic such as penicillin, typically with only one injection or a week-long regimen of pills. Chlamydia, gonorrhea, and syphilis are all bacterial infections that can be cured. However, they can only be cured if you know you're infected, which is why testing is important. Each of these infections can cause serious damage to your body if left untreated and can cause serious complications to an unborn child. Furthermore, the presence of these infections can make HIV infection easier. Just because there is a cure for these infections, does not mean safe sex should be taken lightly. Once infected, you can infect others who may or may not seek testing and treatment.
Whether viral or bacterial, STDs are not to be taken lightly. Practice safe sex and get tested-at least annually if you are sexually active, sooner if you think you may have been exposed.