Genital herpes is a sexually transmitted disease (STD) caused by HSV-2. Nationwide, 16.2% of people have genital HSV-2 infection. Generally, a person can only get HSV-2 infection during sexual contact with someone who has a genital HSV-2 infection.

HSV-1 can cause genital herpes, but it more commonly causes infections of the mouth and lips, so-called "fever blisters." HSV-1 infection of the genitals can be caused by oral-genital or genital-genital contact with a person who has HSV-1 infection.

Blood testing using IgG assays accurately distinguish between HSV-1 and HSV-2 on the basis of differences in the patient's immune response to HSV glycoprotein G (gG). These assays are highly sensitive and specific even in the absence of symptoms. Because antibodies may take several weeks to reach detectable levels after primary infection, negative results should be confirmed by repeat testing three months later.

Chlamydia and gonorrhea (GC/CT) are bacterial STDs especially common among people under 25. It is estimated that 3 million Americans are infected each year. Two-thirds of these people do not experience any symptoms. The bacterium can grow in the reproductive tract in women, and in the urethra in women and men.

GC/CT is spread through virtually any kind of sexual contact. People who have already received treatment may get infected again if they have sexual contact with an infected person.

Diagnosis and treatment are very important to prevent long-term complications and spread of the infection to others. The preferred method of testing currently is the nucleic acid amplification tests (NAAT) utilizing a first-void urine specimen. This test is based on amplification of the DNA that is present in the bacteria.

The human immunodeficiency virus (HIV) is a virus that attacks the cells of the immune system. Although infections may show no clinical signs for years, over time the virus reduces the strength of the immune response and leaves HIV-positive individuals susceptible to other diseases.

HIV is transmitted through bodily secretions. Methods of HIV transmission between adults include sex (oral, vaginal, anal) and sharing needles or syringes with an infected partner.

There are two principal methods of testing for HIV:

ELISA/WB: Enzyme-linked immunosorbent assay with Western Blot confirmation. This test is usually the first one used to detect infection with HIV. If antibodies to HIV are present (positive), the test is repeated. This test has a low chance of a false result after the first few weeks that a person is infected. The Western Blot test is more complex (expensive) than the ELISA to perform, and is done to confirm the results of two positive ELISA tests.

PCR/DNA: Polymerase chain reaction. This test finds either the RNA of the HIV virus or the HIV DNA in white blood cells infected with the virus. This test may be done in a few days after exposure to the virus. Genetic material may be ound even if other tests are negative for the virus. The PCR test is very useful to find a recent infection and to resolve cases where antibody test results were indeterminate.

Hepatitis B and C are viruses that infect the liver. You can have hepatitis B without symptoms. HBV symptoms generally feel like you have the flu. As long as you have the virus, you can spread it to others. Hepatitis C can lead to liver damage as well as cirrhosis liver cancer, and liver failure.

Sometimes these viruses cause a long-term infection that can damage your liver. You may get HCV or HBV if you have sex with an infected person, or share needles with an infected person, or through contact with infected blood. (Experts debate the likelihood of infection through sexual contact)

There are several different HBV tests. The hepatitis B surface antigen (HBsAg) test provides the earliest sign of an active infection. This antigen may be present before symptoms of an HBV infection are present.

Likewise, there are several different HCV tests. Typically, an asymptomatic person will first get a screening test that will show whether he or she has developed antibodies (HCV AB). An antibody is a substance found in the blood that the body produces in response to a virus. Having a positive antibody test means that a person was exposed to the virus at some time in his or her life. If the antibody test is positive, a doctor will most likely order a second test to confirm whether the virus is still present in the person's bloodstream.