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BACKGROUND REPORT MARCH 19, 2009
HIV/AIDS
AIDS, or
acquired immune deficiency syndrome, is a life-threatening, infectious
disease caused by HIV,
a retrovirus that attacks the body's immune system.
The human immunodeficiency
virus hijacks immune system cells, impairing and destroying their function
and weakening the body's ability to fight disease.
When HIV has weakened the immune
system to the point where it has great difficulty fighting opportunistic
infections, the disease has progressed into AIDS. AIDS is considered
the most advanced stage of an HIV infection.
Some of the most common opportunistic
infections for HIV/AIDS patients are tuberculosis, a bacterial infection
that attacks the lungs, PCP pneumonia and cancers caused by Kaposi's
sarcoma.
AIDS was first reported in the United States in 1981,
though some scientists believe it can be traced back to the 1800s. In
the years since the first U.S. case was reported, HIV/AIDS
has grown into a major worldwide epidemic.
According to WHO and UNAIDS estimates, about 33.2 million people were
living with HIV at the end of 2007. About 2.5 million people became
newly infected in 2007 and 2.1 million died of AIDS, including 330,000
children. Two-thirds of HIV infections are in sub-Saharan Africa.
An estimated 420,000 children were newly infected with HIV in 2007,
the vast majority of them through mother to child transmission during
pregnancy, birth or breastfeeding.
In the United States, the CDC
estimates more than 1 million people may be infected with HIV, but 25
percent don't know they are positive. Minority populations are hit
hardest in the United States, according to the Centers for Disease Control
and Prevention: black people are nearly seven times more likely to have
HIV than white people, and Hispanics are three times more likely.
The No. 1 cause of death among the HIV-positive population is the opportunistic
infection tuberculosis, which killed 200,000 people infected with HIV
in 2006, according to WHO.
When HIV enters the body it targets and invadeswhite
blood cells known as CD4 lymphocytes. CD4 cells are part of the body's
immune system and they attack foreign agents that cause disease. HIV uses the cells as factories to
make more virus, which goes on to infect and destroy more immune system
cells. Billions of new HIV particles are produced each day through this
cycle.
When a person reaches the most advanced stages of an HIV infection,
their body is vulnerable to opportunistic infections and their CD4 count
falls to a critically low level. A healthy, uninfected person usually
has between 800 to 1,200 CD4 cells per cubic millimeter of blood. When
that cell count falls below 200 CD4 cells per cubic millimeter of blood,
a person is considered to have AIDS.
HIV is transmitted by the exchange
of bodily fluids or blood between an infected and uninfected person.
It can be transmitted through unprotected vaginal or anal sexual intercourse
and oral sex. The virus can pass into an uninfected person through tiny
tears in the skin or membranes. People who have already been infected
with other sexually transmitted diseases are at an increased risk, as
some STDs can cause open sores or irritation.
HIV can be transmitted by transfusion
of contaminated blood and sharing of contaminated needles, or syringes.
It can also be passed from a mother to her child during pregnancy, childbirth
and from breastfeeding.
HIV is only transmitted when
an infected fluid enters the body. It is not transmitted through hugging,
kissing or shaking hands. HIV is not present in saliva.
The first sign of HIV infection is often a brief flu-like illness with
swollen glands a month or two after infection, but HIV can multiply
in the body for years without showing physical symptoms.
In the absence of medication,
the majority of people infected with HIV will develop signs of related
illness within five to 10 years, but may not be diagnosed with AIDS
until 10 to 15 years after infection, according to the World Health
Organization.
As HIV spreads in the body and the immune system weakens, infected individuals
may experience enlarged lymph nodes, fatigue, weight loss and fevers.
At the most advanced stages, some of the symptoms of opportunistic infections
may besoaking
night sweats, chronic diarrhea, blurred and distorted vision, persistent
fever, cough, white spots and lesions in the mouth.
Common opportunistic infections
that affect people with advanced HIV or AIDS are tuberculosis, herpes,
yeast infection, non-Hodgkin's lymphoma, cancers, PCP pneumonia and
wasting syndrome.
There is no vaccine for HIV,
but there are methods that can be used to prevent transmission. Condoms
are a highly effective means of protection from HIV during sexual activity,
though they can't eliminate the risk entirely because condoms can
break or be used improperly.
Male circumcision has been found to reduce the risk of a man becoming
infected with HIV by about 60 percent, according to the World Health
Organization.
Avoiding contact with other
people's blood can reduce risk of transmission, as well as using clean
needles instead of reusing or sharing a needle.
Mother-to-child transmission
can be reduced to 2 percent or less through antiretroviral therapy administered
to the mother during pregnancy, labor and delivery, and then to the
newborn. A cesarean section may be recommended for women with high viral
loads – the concentration of the
virus in the blood, according
to the Centers for Disease Control.
There is no cure for HIV, but
antiretroviral drugs can prevent or slow the virus from making copies
of itself and keep the amount of virus in the blood low.
Combination therapy with at
least three different antiretroviral drugs is the most effective form
of HIV treatment available. These combinations are often called medication
"cocktails."
When combination therapy was
first approved in 1995 it was a breakthrough that helped decrease the
AIDS death rate in the United States by nearly 50 percent by 1997.
Drug resistance is a growing
problem in the treatment of HIV. Adherence to a drug regime is extremely
important to help suppress replication of HIV and reduce mutations of
the virus that can cause drug resistance.
But perfect adherence every day over years and years is very difficult,
and more and more people are being infected with HIV strains that already
have some drug resistance. Newer, more expensive drugs will continuously
need to be developed as drug resistance spreads.
Sources: CDC, World Health Organization,
Johns Hopkins University, National Institute of Allergy and Infectious
Diseases |
