One of the most widely publicized diseases, AIDS is marked by progressive weakening of the immune system, which makes a person vulnerable to opportunistic infections and unusual cancers. The syndrome was first defined by the Centers for Disease Control and Prevention in 1981. Since then, the agency has revised its definition of AIDS, most recently in 1993.Homosexual and bisexual men who are sexually active witl1 many partners have the highest risk for contracting AIDS. Other high-risk groups include intravenous drug users and hemophiliacs, especially those who’ve been treated with Factor VIII (one of the blood clotting factors) concentrate. Most recently, heterosexual partners and children of persons with AIDS or of those in high-risk groups and persons receiving multiple blood transfusions have been added to the high-risk category. Drug therapy and prevention and treatment of common opportunistic infections can delay the natural progression of HI V infection and prolong survival.

To reduce the risk of contracting AIDS, public health advocates recommend following safe sex practices, such as condom use.

What Causes it?

AIDS is caused by a retrovirus called human immunodeficiency virus (HIV). The retrovirus strikes cells bearing a substance called the CD4 antigen. This antigen serves as a receptor for HIV and lets it enter the cell. HIV prefers to infect CD4+ cells, which are white blood cells that are sometimes called helper cells. But it may also infect other cells. including certain digestive tract cells, uterine cervical cells, and neuroglial cells, a type of nerve cell.

After HIV invades a cell, it reproduces. Recent research shows that in the first weeks after infection, HIV is extremely active. It eventually causes profound illness by hindering the immune system’s ability to fight disease.

The infection process takes three forms:

immunodeficiency - opportunistic infections and unusual cancers

autoimmunity - the body’s reaction against its own tissues

neurologic problems - AIDS dementia, a brain condition known as HIV encephalopathy, and peripheral nerve disorders.

Transmission modes

HIV is transmitted by intimate sexual contact, especially during rectal intercourse that injures the mucous membranes; by transfusion of contaminated blood or blood products (this risk has diminished thanks to routine testing of all blood products); by sharing of contaminated needles; and by transmission from an infected mother to her fetus (by cervical or blood contact at delivery and in breast milk). Mounting evidence suggests that HIV is not transmitted by casual household or social contact.

What are its symptoms?

Some people with AIDS lack symptoms until they suddenly develop an opportunistic infection or the purple skin lesions of Kaposi’s sarcoma, one of the cancers associated with AIDS.

But more often, they have nonspecific signs and symptoms, such as fatigue, afternoon fevers, night sweats, weight loss, diarrhea, or cough. Soon after these appear, they typically develop several infections at the same time.

In children with AIDS, the time between exposure to HIV and appearance of symptoms seems to be shorter (an average of 8 months). Signs and symptoms resemble those of adults with AIDS, except for those related to sexually transmitted disease. Finally, in children, the most common manifestation and cause of death isn’t Pneumocystis carinii pneumonia, as in adults, but diffuse interstitial pneumonitis.

How is it diagnosed?

According to the Centers for Disease Control and Prevention, a diagnosis of AIDS is confirmed by the presence of an opportunistic infection with lab evidence of HIV infection and a CD4+ T-cell count of less than 200 cells per microliter.

How is it treated?

Currently, no cure exists for AIDS. However, the drug Retrovir (known as AZT) is used alone or along with other drugs, such as Hivid, to inhibit HIV reproduction. Videx may be used if a person can’t tolerate AZT or no longer responds to it.

Supportive measures aim to reduce the person’s risk of infection, treat existing infections and cancers, maintain adequate nutrition, and provide emotional support.

Additional drug treatment

Although drugs can eliminate many of the organisms that cause opportunistic infections, these infections tend to recur once drug treatment stops. The drug of choice for P. carinii pneumonia is oral or intravenous Bactrim or Septra. If this treatment fails or if toxicity occurs, the person may be given NebuPent or Pentam 300. However, this drug may cause liver problems, a rapid pulse, low blood pressure, low blood sugar, and rashes.

To treat Kaposi’s sarcoma, the person may receive chemotherapy drugs, such as Oncovin and VePesid. Unfortunately, aggressive treatment of this cancer makes infection more likely. An interferon alfa drug is also being used to treat Kaposi’s sarcoma. Radiation and laser therapy can relieve, but not cure, local Kaposi’s lesions.

To treat retinitis, the person may receive Foscavir or Cytovene.