The human immunodeficiency virus (HIV) is a lentivirus (a subgroup of retrovirus) that causes the acquired immunodeficiency syndrome (AIDS), a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive. The virus attaches to immune system cells, particularly the helper T cells, which regulate much of the body's immune response. From there, the retrovirus uses your cells to replicate, killing many of those infected host cells in the process.
Scientists believe a virus similar to HIV first occurred in some populations of chimps and monkeys in Africa, where they're hunted for food. Contact with an infected monkey's blood during butchering or cooking may have allowed the virus to cross into humans and become HIV.
Since its discovery, AIDS has caused an estimated 36 million deaths worldwide, and approximately 35.3 million people are living with HIV globally as of 2012. HIV/AIDS is considered a pandemic.
Three main stages of HIV infection:
Acute infection
The initial period following the contraction of HIV is called acute HIV, primary HIV or acute retroviral syndrome. Many individuals develop symptoms 2-4 weeks post exposure while others have no significant symptoms. Symptoms occur in 40-90% of cases.
Clinical latency
The initial symptoms are followed by a stage called clinical latency, asymptomatic HIV, or chronic HIV. Without treatment, this second stage of the natural history of HIV infection can last from about three years to over 20 years (on average, about eight years).
Acquired Immunodeficiency Syndrome
AIDS is the most advanced stage of HIV disease. A person is diagnosed with AIDS when their immune system is too weak to fight off infections. In the absence of specific treatment, around half of people infected with HIV develop AIDS within ten years.
Symptoms
The symptoms of HIV and AIDS vary, depending on the phase of infection.
Primary infection
The majority of people infected by HIV develop a flu-like illness within a month or two after the virus enters the body. This illness, known as primary or acute HIV infection, may last for a few weeks. Possible signs and symptoms include:
- Fever
- Headache
- Muscle aches
- Rash
- Chills
- Sore throat
- Mouth or genital ulcers
- Swollen lymph glands, mainly the neck
- Joint pain
- Night sweats
- Diarrhea
Although the symptoms of primary HIV infection may be mild enough to go unnoticed, the amount of virus in the bloodstream (viral load) is particularly high at this time. As a result, HIV infection spreads more efficiently during primary infection than during the next stage of infection.
Clinical latent infection
In some people, persistent swelling of lymph nodes occurs during clinical latent HIV. Otherwise, there are no specific signs and symptoms. HIV remains in the body, however, and in infected white blood cells. Clinical latent infection typically lasts eight to 10 years. A few people stay in this stage even longer, but others progress to more severe disease much sooner.
As the virus continues to multiply and destroy immune cells, you may develop mild infections or chronic signs and symptoms such as:
- Fever
- Fatigue
- Swollen lymph nodes - often one of the first signs of HIV infection
- Diarrhea
- Weight loss
- Cough
- Shortness of breath
Progression to AIDS
If you receive no treatment for your HIV infection, the disease typically progresses to AIDS in about 10 years. By the time AIDS develops, your immune system has been severely damaged, making you susceptible to opportunistic infections - diseases that wouldn't trouble a person with a healthy immune system.
The signs and symptoms of some of these infections may include:
- Soaking night sweats
- Shaking chills or fever higher than 100 F for several weeks
- Cough
- Shortness of breath
- Chronic diarrhea
- Persistent white spots or unusual lesions on your tongue or in your mouth
- Headaches
- Persistent, unexplained fatigue
- Blurred and distorted vision
- Weight loss
- Skin rashes or bumps
Transmission
You can become infected with HIV in several ways, including:
- By having vaginal, anal or oral sex with an infected partner whose blood, semen or vaginal secretions enter your body. The virus can enter your body through mouth sores or small tears that sometimes develop in the rectum or vagina during sexual activity.
- From blood transfusions. In some cases, the virus may be transmitted through blood transfusions. American hospitals and blood banks now screen the blood supply for HIV antibodies, so this risk is very small.
- By sharing needles. HIV can be transmitted through needles and syringes contaminated with infected blood.
- During pregnancy or delivery or through breast-feeding. Infected mothers can infect their babies.
Complications
HIV infection weakens your immune system, making you highly susceptible to numerous infections and certain types of cancers. Without treatment, average survival time after infection with HIV is estimated to be 9 to 11 years, depending on the HIV subtype.
Infections common to HIV/AIDS
- Tuberculosis
- Salmonellosis
- Cytomegalovirus
- Candidiasis
- Cryptococcal meningitis
- Toxoplasmosis
- Cryptosporidiosis
Cancers common to HIV/AIDS
- Kaposi's sarcoma
- Lymphomas
Other complications
- Wasting syndrome - It's defined as a loss of at least 10 percent of body weight, often accompanied by diarrhea, chronic weakness and fever.
- Neurological complications. Although AIDS doesn't appear to infect the nerve cells, it can cause neurological symptoms such as confusion, forgetfulness, depression, anxiety and difficulty walking. One of the most common neurological complications is AIDS dementia complex, which leads to behavioral changes and diminished mental functioning.
- Kidney disease. HIV-associated nephropathy (HIVAN) is an inflammation of the tiny filters in your kidneys that remove excess fluid and wastes from your bloodstream and pass them to your urine. Because of a genetic predisposition, the risk of developing HIVAN is much higher in blacks.
Treatments
There's no cure for HIV/AIDS, but a variety of drugs can be used in combination to control the virus. Each class of anti-HIV drugs blocks the virus in different ways. It's best to combine at least three drugs from two classes to avoid creating strains of HIV that are immune to single drugs.
Vaccination
There's no vaccine to prevent HIV infection and no cure for AIDS.
Prevention
It is possible to protect yourself and others from infection by avoiding any behavior that allows HIV infected fluids into your body.