If you have HIV, you have an infection

that damages your immune system over time, and causes AIDS.

AIDS stands for Acquired Immunodeficiency Syndrome.

It is the final stage of an HIV infection, when

your immune system is damaged and too weak

to fight off ordinary infections.

When foreign invaders, such as bacteria and viruses,

get into your body, they can cause infections.

These events activate your body's defenses.

The white blood cells of your immune system

are part of your body's defenses.

One type of white blood cell, called

helper T lymphocytes, or helper T cells,

strengthen your immune system's response to infection

in two ways.

First, helper T cells release chemicals

that attract other white blood cells

to the site of the infection.

These additional white blood cells

attack the invading bacteria or virus, as well as

other infected cells.

Second, helper T cells release chemicals

that cause other white blood cells to multiply.

These new white blood cells create markers,

called antibodies, which can identify

the same foreign invader throughout your body.

Antibodies attach to the bacteria or virus,

marking them as targets for your immune system to destroy them.

If you have HIV, it travels through your blood

and other body fluids to infect and kill certain white blood cells.

The virus enters helper T cells, which are the primary target.

Once inside, the virus makes many copies of itself.

As these virus particles are made,

they leave the damaged helper T cell to infect other cells.

The T cell loses its ability to protect the body

from the ongoing infection and dies.

In this way, HIV spreads and kills

more of your helper T cells, weakening your immune system.

As a result, other types of infections

are able to take advantage of your body's inability

to defend itself.

These infections are called opportunistic infections.

If you have an HIV infection, and one or more

opportunistic infections, you have AIDS.

Some of the common AIDS-related opportunistic infections

are inflammation of the tissues covering your brain and spinal

cord, called meningitis, inflammation of your brain,

called encephalitis.

Respiratory illnesses, such as pneumonia and tuberculosis.

Intestinal illnesses, such as chronic diarrhea

caused by infectious parasites.

And cancers, such as Kaposi's sarcoma

and non-Hodgkin lymphoma.

HIV passes from person to person through infected body fluids.

HIV can enter your body during unprotected sex, while sharing

drug injection needles, during your own childbirth,

while breastfeeding from your mother,

or from contaminated blood or blood products.

Although there is no cure for HIV,

drugs called antiretroviral medications

can reduce the amount of HIV in your body.

One class of antiretroviral medication,

called entry or fusion inhibitors,

disrupts the HIV infection process

by preventing the virus from attaching to your cells.

Other classes of antiretroviral medications

include reverse transcriptase inhibitors,

protease inhibitors, and integrase inhibitors.

These drugs prevent the creation, assembly, and spread

of new viruses.

Your doctor may prescribe a combination of these drug

classes, known as highly active antiretroviral therapy,

or HAART.

Antiretroviral medication doesn't completely

remove HIV from your body, but slows it down enough

to enable your immune system to fight infections.

Regular blood tests will let your doctor

know how effective your antiretroviral medication is

in controlling HIV.

If the number of helper T cells is high enough in your blood

sample, your medication is working.

Treatments for the opportunistic infections of AIDS

are medications specific for each type of infection.

For example, your doctor may prescribe antibiotics

if you have pneumonia or tuberculosis.

To avoid getting or spreading an HIV infection,

know your HIV status and your partner's status

by getting tested regularly.

The most effective way to prevent HIV infection

is to avoid vaginal and anal sex.

When engaging in sexual activity,

you will be less likely to contract HIV

if you only have sex with one uninfected partner,

or use latex condoms for protection.

Avoid using injectable illegal drugs, or sharing drug needles,

because the needles may have the virus on them.

Avoid intoxication from drugs or alcohol,

because you will be more likely to engage

in unsafe sexual behavior.