The human immunodeficiency virus (HIV) infects cells of the immune system, destroying or impairing their function. Infection with the virus results in the progressive deterioration of the immune system, leading to "immune deficiency." The immune system is considered deficient when it can no longer fulfil its role of fighting infection and disease. Infections associated with severe immunodeficiency are known as "opportunistic infections", because they take advantage of a weakened immune system.

Acquired immunodeficiency syndrome (AIDS) is a term which applies to the most advanced stages of HIV infection. It is defined by the occurrence of any of more than 20 opportunistic infections or HIV-related cancers.

HIV can be transmitted through unprotected sexual intercourse (vaginal or anal), and oral sex with an infected person; transfusion of contaminated blood; and the sharing of contaminated needles, syringes or other sharp instruments. It may also be transmitted between a mother and her infant during pregnancy, childbirth and breastfeeding.

According to estimates by WHO and UNAIDS, 34. million people were living with HIV at the end of 2011. That same year, some 2.5 million people became newly infected, and 1.7 million died of AIDS-related causes, including 230 000 children.

The length of time can vary widely between individuals. Left without treatment untreated, the majority of people infected with HIV will develop signs of HIV-related illness within 5-10 years, although this can be shorter. The time between acquiring HIV and an AIDS diagnosis is usually can be 10-15 years, but sometimes longer. Antiretroviral therapy (ART) can slow the disease progression by preventing the virus replicating and therefore decreasing the amount of virus in an infected person's blood (known as the 'viral load').

Tuberculosis (TB) kills nearly a quarter of a million people living with HIV each year. It is the number one cause of death among HIV-infected people in Africa, and a leading cause of death in this population worldwide. There are a number of core health care strategies that are critical to prevent and manage TB infection among people living with HIV:

- intensified case finding for active TB
- isoniazid preventive treatment
- TB infection control
- early initiation of antiretroviral therapy.

Knowing one's HIV status can have two important benefits.

- If someone learns that he/she is HIV positive, they can take steps before symptoms appear to access treatment, care and support, thereby potentially prolonging their life and preventing health complications for many years.
- If they know that they are infected, they can take precautions to prevent the spread of HIV to others.

Antiretroviral drugs are used in the treatment and prevention of HIV infection. They fight HIV by stopping or interfering with the reproduction of the virus in the body, reducing the amount of virus in the body.

More than eight million people in low- and middle-income countries were receiving HIV antiretroviral therapy at the end of 2011. Until 2003, the high cost of the medicines, weak or inadequate health care infrastructure, and lack of financing prevented wide use of combination antiretroviral treatment in low- and middle-income countries. But in recent years, increased political and financial commitment has allowed dramatic expansion of access to treatment.

No, there is no cure for HIV. But with good and continued adherence to antiretroviral treatment, the progression of HIV in the body can be slowed to a near halt. Increasingly, people living with HIV can remain well and productive for extended periods of time, even in low-income countries.

In addition to antiretroviral treatment, people with HIV often need counselling and psychosocial support. Access to good nutrition, safe water and basic hygiene can also help an HIV-infected person maintain a high quality of life.

No. Being diagnosed with HIV does NOT mean a person will also be diagnosed with AIDS. Healthcare professionals diagnose AIDS only when people with HIV disease begin to get severe opportunistic infections (OI), or their T-cell counts fall below a certain level.

HIV is found only in body fluids, so one cannot get HIV by shaking someone's hand or giving them a hug (or by using the same toilet or towel). While HIV is found in saliva, sharing cups or utensils has never been shown to transmit HIV.

No, Insects can NOT transmit HIV. Research has shown that HIV does not replicate or survive well in insects. In addition, blood-eating insects digest their food and do not inject blood from the last person they bite into the next person.

No. One cannot get HIV from casually kissing someone (or vice versa) who has HIV. Skin is a greater barrier against HIV. It is not recommended to engage long, open mouth kissing ("French Kissing") with someone who has HIV and one has an open sore in or around the mouth.

No. HIV diagnostic tests cannot determine who passed the infection to the negative partner.

In general, no. A skilled healthcare provider can generally estimate how long someone has been infected by looking at the levels of virus in the body, their CD4 (T-cell) count, and whether or not they have had any opportunistic infections. If someone is currently suffering from symptoms of acute HIV infection, a healthcare provider can usually conclude that infection occurred within the past few weeks.

While complications from HIV infection remain a possibility, current treatments and medications are giving people with HIV a positive prognosis and near-normal life-span. This makes patients living with HIV vulnerable to the same health conditions that affect all people as they age. This is why it is important to maintain good health throughout one's life.

The health care provider will probably check one's CD4 count at his/her first visit. Then-depending on what his/her counts are and whether both decide it's time to begin treatment-one can usually expect to undergo viral load testing every 3-6 months. Typically, once someone with HIV is on a good medication regimen, have an undetectable viral load, and have an increasing CD4 count, they will take a viral load test every 6 months.

Germs in food and water that can make someone with HIV ill include E.coli, Salmonella, Campylobacter, Listeria and Cryptosporidium. They can cause diarrhea, upset stomach, vomiting, stomach cramps, fever, headache, muscle pain, bloodstream infection, meningitis, or encephalitis.