Causes for HIV/AIDS
HIV is transmitted when the virus enters the body, usually by injecting infected cells or semen. There are several possible ways in which the virus can enter.
Most commonly, HIV infection is spread by having sex with an infected partner. The virus can enter the body through the lining of the vagina, vulva, penis, rectum, or mouth during sex.
HIV frequently spreads among injection-drug users who share needles or syringes that are contaminated with blood from an infected person.
Women can transmit HIV to their babies during pregnancy or birth, when infected maternal cells enter the baby's circulation.
HIV can be spread in health-care settings through accidental needle sticks or contact with contaminated fluids.
Very rarely, HIV spreads through transfusion of contaminated blood or blood components. Blood products are now tested to minimize this risk. If tissues or organs from an infected person are transplanted, the ...view middle of the document...
Many people do not develop symptoms after they first get infected with HIV. Others have a flu-like illness within several days to weeks after exposure to the virus. They complain of fever, headache, tiredness, and enlarged lymph nodes in the neck. These symptoms usually disappear on their own within a few weeks. After that, the person feels normal and has no symptoms. This asymptomatic phase often lasts for years.
The progression of disease varies widely among individuals. This state may last from a few months to more than 10 years.
During this period, the virus continues to multiply actively and infects and kills the cells of the immune system.
The virus destroys the cells that are the primary infection fighters, a type of white blood cell called CD4 cells.
Even though the person has no symptoms, he or she is contagious and can pass HIV to others through the routes listed above.
AIDS is the later stage of HIV infection, when the body begins losing its ability to fight infections. Once the CD4 cell count falls low enough, an infected person is said to have AIDS. Sometimes, the diagnosis of AIDS is made because the person has unusual infections or cancers that show how weak the immune system is.
The infections that happen with AIDS are called opportunistic infections because they take advantage of the opportunity to infect a weakened host. The infections include (but are not limited to)
pneumonia caused by Pneumocystis, which causes wheezing;
brain infection with toxoplasmosis which can cause trouble thinking or symptoms that mimic a stroke;
widespread infection with a bacteria called MAC (mycobacterium avium complex) which can cause fever and weight loss;
yeast infection of the swallowing tube (esophagus) which causes pain with swallowing;
widespread diseases with certain fungi like histoplasmosis, which can cause fever, cough, anemia, and other problems.
A weakened immune system can also lead to other unusual conditions:
lymphoma in (a form of cancer of the lymphoid tissue) the brain, which can cause fever and trouble thinking;
a cancer of the soft tissues called Kaposi's sarcoma, which causes brown, reddish, or purple spots that develop on the skin or in the mouth.