An overview of HIV and AIDS: transmission, diagnosis, treatment, and prevention.

What Is AIDS?

AIDS is short for acquired immune deficiency syndrome. AIDS is a disease that slowly destroys the body's immune system. Without these important defenses, a person with AIDS can't fight off germs and cancers.

HIV is the virus that causes AIDS. It kills an important kind of blood cell -- the CD4 T lymphocyte, or T cell. These T cells are the quarterbacks of the immune system. As they die off, the body becomes more and more vulnerable to other diseases. Germs take this opportunity to invade the body. The diseases they cause are called opportunistic infections (OIs for short). When people with HIV get these infections -- or when their CD4 T-cell levels get too low -- they have AIDS.

Usually it takes many years for HIV to weaken the body's immune system to the point of AIDS. Anti-HIV drugs help prevent this. Even when a person already has AIDS, the drugs can help a person get better.

Anti-HIV drugs let many people with HIV infection live healthy lives. Combinations of these powerful medicines work very well, but they often have serious side effects, such as vomiting, diarrhea, and fatigue. And people with HIV have to keep taking these drugs every day for the rest of their lives. Ask anyone who's taking these "drug cocktails" -- it's best to avoid getting HIV in the first place.

AIDS is a worldwide epidemic. Most cases are in Africa, but the disease is spreading most rapidly in Eastern Europe and Asia. Even if a cure were found tomorrow, AIDS will be the most deadly disease ever to plague mankind.

What Causes It?

HIV -- human immunodeficiency virus -- causes AIDS. HIV infection is for life. There is no cure, but anti-HIV drugs keep HIV in check. Unfortunately, 95% of the world's HIV infected people cannot afford this medicine.

There are a few people who say HIV does not cause AIDS. Some are scientists, but none of them are AIDS experts. They offer only false hope and no answers. Overwhelming medical and scientific evidence shows that HIV is the AIDS virus. Every major health organization in the world says that HIV is a killer.

There are two main types of HIV -- HIV-1 and HIV-2. HIV-2 is rare outside Africa.

You can't catch HIV unless another person's body fluids -- blood, semen, or vaginal secretions -- enter your bloodstream. This can happen through the tip of the penis, through the vagina, through the rectum, or through an open wound.

HIV is spread:

• By having sex without a condom. Vaginal and anal sex carry a high risk. The risk of getting HIV from oral sex is low.

• By sharing needles and/or syringes to inject drugs or steroids.

• From a mother to her infant during pregnancy, delivery, or breastfeeding.

• By getting a tattoo or piercing from a dirty needle.

• By transfusions, blood products, or organ transplants. This kind of transmission no longer happens in developed countries, which test all donated blood and organs for HIV.

• You can't get HIV from a toilet seat or from touching an infected person. You can't get HIV from being sneezed or coughed or spit on by an infected person. You can't get HIV from kissing (although there is a theoretical risk from very deep "French" kissing). You can't get HIV from a mosquito, flea, or tick bite.

What Are the Symptoms?

HIV infection comes in three stages: acute infection, chronic infection, and AIDS.

Acute HIV infection is the earliest and shortest stage of HIV infection. Not everyone gets symptoms, but most people come down with a flu-like illness three to six weeks after infection. The symptoms are the same as flu or mononucleosis: fever and fatigue lasting for a week or two. There may or may not be other symptoms:

• A blotchy red rash, usually on the upper torso, that does not itch

• Headache

• Aching muscles

• Sore throat

• Swollen lymph glands

• Diarrhea

• Nausea

• Vomiting

IMPORTANT: If you have been at risk of getting HIV and then come down with these flu-like symptoms, tell a doctor right away. Sensitive new tests can tell whether you have acute HIV infection. Treatment during the acute stage of HIV infection works much, much better than later treatment. Be sure to tell your doctor about your HIV risk. If you don't, you may not get the right tests. Standard HIV tests -- either home tests or lab tests -- won't detect acute HIV infection.

The body puts up a terrific struggle against HIV. At the end of this struggle, the body reaches a kind of standoff with the virus. This is chronic HIV infection, which begins three to six months after a person gets HIV. There aren't any symptoms. For most people, this stage of HIV infection lasts about 10 years.

Even though there are no symptoms, the immune system slowly runs down. A normal person has a CD4 T-cell count of 450 to 1,200 cells per microliter. When people with HIV have their T-cell counts drop to 200 or lower, they have reached the stage of AIDS.

AIDS itself has no symptoms. Because the immune system is devastated, disease symptoms are specific to the kind of infections a person may have. When a person's T cells get very low, doctors prescribe drugs to prevent infections.

Sometimes people don't seek medical help until they have AIDS. They may have some of the following symptoms:

• Being tired all the time

• Swollen lymph nodes in the neck or groin

• Fever lasting more than 10 days

• Night sweats

• Unexplained weight loss

• Purplish spots on the skin that don't go away

• Shortness of breath

• Severe, long-lasting diarrhea

• Yeast infections in the mouth, throat, or vagina

• Easy bruising or unexplained bleeding

Call your doctor if you have any of these symptoms.

How Do I Know If I Have HIV?

The only way to know for sure if you have HIV is to get an HIV test.

If you are at risk of HIV, you should have an HIV test every six months. You should also reduce your risk (see the section on Prevention).

Soon after HIV infection, the body begins to make antibodies that fight the virus. The HIV test looks for these antibodies in your blood. After about three months, most people have enough anti-HIV antibodies to test positive on standard HIV tests. Some people don't test positive for six months or even a year, so repeat testing is needed.

The HIV test is simple. Home tests are available. You can also get tested at labs that keep your identity secret. You can also get tested by your doctor, and at your public health department. If you are doing a home test, or if you order a test from a lab, a positive result means you should see a doctor to confirm that you're really infected.

If you know you are at high risk of HIV infection and come down with a bad case of the flu, see a doctor right away. It could be the early signs of HIV infection. Tell your doctor about your risk behavior. There are very sensitive tests that can tell if you've got HIV -- and treatment during this very early stage of infection works best.

Before getting tested, think about what your test result will mean. Most people need help with this, so see a counselor, psychologist, or doctor for advice -- or call your local AIDS hotline. Prepare for your result.

If you test negative, you may want to talk about how to reduce your future risk. There are many private AIDS organizations that can give you this kind of help. Usually these organizations have "been-there, done-that" counselors you can relate to.

If you test positive, you'll need help deciding what to do. HIV infection isn't a death sentence. It does mean that you will need to take special care of your health. It also means that you will have to take special care not to infect anybody else with the AIDS virus.

If you test positive for HIV, you must have medical care. If you don't have a doctor, a local AIDS organization or AIDS hotline can help you find one. Get some help from a person you trust. If you don't have a person like this in your life, get help from a professional counselor. Have this person go with you to the doctor.

If you test positive, you have to tell your sex and/or needle-sharing partners that they, too, need to be tested. But you don't have to tell everybody else. Tell only those people who can support you. If you have children, talk with a counselor about what to tell them, and when.

What Are the Treatments?

Treatment with combinations of AIDS drugs can keep people with HIV from getting AIDS.

In clinical studies, where everybody gets state-of-the art treatment and very regular medical exams, the drugs work for the vast majority of people. In the real world, some AIDS doctors say, the drugs fail in about half of their patients.

Why? Not all AIDS drugs work for all people. It's absolutely essential to take the drugs at the right time of day, every single day. Sometimes the drugs' side effects -- or simple human nature -- make this very hard to do. And because HIV is constantly mutating, no two people are infected with exactly the same virus.

Treatment must be planned and adjusted for every individual person with HIV. When to start treatment is a big question. Everybody agrees that starting aggressive treatment in the early days after infection -- the stage of acute HIV infection -- is most effective. But most people don't find out they have HIV until the stage of chronic HIV infection, when the virus has a firm hold on the body. There's no hard and fast rule about when to start treatment for such patients.

Most AIDS/HIV doctors now recommend holding off on treatment until a person's immune system starts to fail. This decision is based on the CD4 T-cell count, the best measure of HIV disease. Another factor is how much HIV is in the blood -- a measure called viral load.

When treatment begins, the decision on which anti-HIV drugs to use is crucial. New tests can tell which drugs will work best on the HIV infecting an individual patient.

There are several types of anti-HIV drugs. Because HIV mutates so quickly, it soon is able to resist any single treatment. That's why doctors use combinations ("cocktails") of anti-HIV drugs. Virus that's resistant to one drug gets killed by another. Over time, even this strategy isn't always enough, and virus resistant to multiple drugs may appear. At this point, a doctor will switch to another drug combination. While there are many AIDS drugs, the possibilities are not endless. Researchers are working hard to find new ways to treat patients who have run through several different combination treatments.

The different types of anti-HIV drugs each target a different aspect of HIV's life cycle:

• Entry. HIV has to get into a T cell to start its dirty work. First it has to latch on to the cell. Next it has to fuse its own outer membrane to that of the cell. New drugs called attachment inhibitors and fusion inhibitors are being tested in humans.

• Early replication. HIV's goal is to take over a T cell's genetic machinery. After fusing with a cell, the virus spills its genetic material into the cell. HIV has a problem here -- its genetic code is written in a form called RNA. But in humans, our genetic code is written in DNA. HIV solves this problem by making an enzyme -- called reverse transcriptase or RT -- that translates its RNA into DNA. The class of AIDS drugs called nucleoside RT inhibitors ("Nukes") fools HIV into making flawed reverse transcriptase out of bogus raw materials. Another class -- the non-nucleoside RT inhibitors or Non-Nukes -- gums up reverse transcriptase so it doesn't work. Several Nukes and Non-Nukes are now in use.

• Late replication. HIV has to snip apart the cell's DNA, put its own DNA in, and sew the DNA strand back together. The sewing kit it needs to do this is called integrase. Human tests of an integrase inhibitor began in 2001.

• Assembly. Once HIV has taken over a cell's genetic material, it gets the cell to make the pieces from which a new virus is made. These pieces have to be cut into the right size -- and that's what HIV's protease enzyme does. Several protease inhibitors (or PIs) are now on the market.

Another approach is to make the body's immune system fight HIV more effectively. One way to do this is with a chemical messenger called interleukin-2 or IL-2, now in advanced human tests. Other immune stimulators are in various stages of development.

Yet another strategy is to use antisense drugs. These are strands of genetic material that form a kind of mirror image of HIV's genetic code. This throws a monkey wrench into the virus's replication machinery. One antisense drug has entered human tests.

Side effects are common with all of these medications. These can include:

• Nausea and vomiting. These side effects are most common in the first weeks or months of anti-HIV treatment. Often they go away as the body gets used to the drugs.

• Diarrhea. Most common early in treatment. Call your doctor if diarrhea lasts for more than three days.

• Rash. Rash is common among people who start taking anti-HIV drugs. Usually it goes away by itself. IMPORTANT: Rash could be a sign of an allergic reaction to a drug. This happens more often to patients taking Ziagen, but also happens to a few patients taking Viramune, Rescriptor, or Sustiva. If you get a rash after taking these drugs, call your doctor right away.

• Problems falling asleep or staying asleep.

• Fatigue.

• Dry skin and/or ingrown toenails sometimes happen with Crixivan.

• Pain, numbness, tingling, and or burning in the hands and/or feet.

• Kidney stones sometimes occur in people who take Crixivan.

• Changes in the way your body deals with fat. This is called lipodystrophy syndrome. It includes a range of symptoms including a roll of fat between the shoulders ("buffalo hump"); enlarged breasts; and loss of fat in the face, arms, and legs.

How Can I Prevent AIDS?

It doesn't matter who you are. What matters is how you act. There aren't any AIDS risk groups -- only AIDS risk behaviors.

The most common way people get HIV is by having sex with an infected person. You can't tell by looking at a person whether they have HIV. This means you have to protect yourself -- and your sex partner. How can you do this?

• Don't have sex outside marriage or a committed relationship. If you or your partner have ever had unprotected sex -- or if either of you uses injection drugs -- you can't be sure you don't have HIV. The only way to be sure is to get tested. This means two HIV tests six months apart, with no new sex partners or injection drug use in between.

• You can't get HIV if your penis, mouth, vagina, or anus doesn't touch another person's penis, mouth, vagina, or anus. Kissing, erotic massage, and mutual masturbation are safe sex activities.

• You can greatly reduce your risk by using a latex or polyurethane condom during sex. Don't use natural-skin condoms -- they prevent pregnancy but don't prevent infections. Learn the right way to use a condom. Use a condom as soon as the man has an erection, not just when he's ready to ejaculate. Use a lubricant -- but NEVER use an oil-based lubricant with a latex condom. The female condom (also called a vaginal pouch) also protects against disease.

• Oral sex without a condom or latex dam is not safe, but it's far safer than unprotected intercourse.

Using drugs increases your HIV risk. Stop using drugs if you want to avoid the AIDS virus. If you're not ready to stop taking drugs, you can still reduce your risk of getting HIV. Here's how:

• Don't have sex when you're high. It's easy to forget about safe sex when you're on drugs.

• If you must use drugs, don't inject them.

• If you must inject drugs, don't share the equipment. This includes the whole works: needles, syringes, cookers, cotton, and rinse water. Some states have needle-exchange programs where you can trade dirty equipment for new equipment.

Mothers with HIV can give the virus to their infants during pregnancy, delivery, or breastfeeding. If you're pregnant, get an HIV test. Anti-HIV drugs taken during pregnancy and delivery can greatly reduce the risk of passing the AIDS virus to your baby. If you have HIV, you should feed your infant formula, or breast milk from an uninfected woman.

You can get HIV from the blood of an infected person. If you are helping a bleeding person, be careful to avoid getting blood into cuts or open sores on your skin or in your eyes or mouth.

If you think you have been exposed to HIV, see your doctor immediately. Your doctor may recommend taking anti-AIDS drugs to keep the virus from taking hold. This is NOT a "morning-after pill" -- it's several weeks of drugs with serious side effects -- but it can keep you from getting HIV infection.

American Foundation for AIDS Research

AIDS Research Information Center