blood supplies has significantly reduced this risk
and infection through blood products is now
uncommon.
Though there are numerous treatments for
HIV/AIDS, there is no cure. HIV, the infection,
nearly always progresses to AIDS, the illness, over
the course of 5 to 20 years. Aggressive treatment
can further manage the symptoms and complica-
tions of AIDS for years to sometimes decades.
However, AIDS is ultimately fatal. AIDS does not
itself cause death but instead so extensively dam-
ages theIMMUNE SYSTEM, the infection’s target, that
the body cannot protect itself from infections or
conditions such as cancer, which become the
causes of death.
The Virus: HIV
The human immunodeficiency virus, HIV, is a
retrovirus that exists in two known types, HIV-1
and HIV-2. Each infects the body in the same way
and etches the same pathway to AIDS. HIV-1 is
predominant in North America and Europe; HIV-2
is predominant in Africa, Southeast Asia, and
China. HIV enters the body by attaching itself to a
type of T-CELL LYMPHOCYTEcalled a CD4 cell (helper
T-cell). CD4 cells direct the immune system’s
response to infection and are integral to CELL-MEDI-
ATED IMMUNITY. Once attached, the HIV virion, the
essential structure of the VIRUSbefore it acquires a
host cell, can infiltrate the cell without the
immune system detecting its presence.
As a retrovirus, HIV uses reverse transcriptase,
an enzyme, to instruct the CD4 cell’s RNAto repli-
cate the virus’s RNA in place of the cell’s DNA. The
cell then supports and replicates the virus, releasing
new virions to infect additional CD4 cells. The
entire process is quite stealthy. Therapeutic inter-
ventions are not quite of comparable stealth,
though are getting closer to the mark. For example,
ANTIVIRAL MEDICATIONScalled nucleoside analogs can
interject themselves into the process of reverse
transcription, with the result that the cell produces
“blank” DNA that fails to replicate the virus.
The Illness: AIDS
The ultimate outcome, at present, of HIV infection
is the collapse of the immune system. Eventually
the number of CD4 cells under HIV control is sig-
nificantly greater than the number of CD4 cells
under control of the immune system. Critical mass
shifts and the immune system becomes deficient:
It lacks the resources to rally against even the
most minor of infections. Illness ranging from CAN-
DIDIASIS (yeast infection) to AIDS-related lym-
phoma (a type of cancer) takes over. It is these
illnesses, not HIV/AIDS, that causes death.Symptoms and Diagnostic Path
About two weeks after infection with HIV, mild
flulike symptoms appear that last 10 to 14 days.
Most people do not recognize these symptoms as
HIV infection. After these initial symptoms
resolve, there are no further symptoms until AIDS
emerges. However, HIV antibodies become present
in the body three to six months after infection
(called seroconversion). Various tests are available
to detect the presence of HIV antibodies, which
confirm that a person has HIV infection (is HIV-
positive). HIV infection is not the same as AIDS.
AIDS is the end-stage outcome of HIV infection.
At present the diagnostic criteria for the transition
from HIV infection to AIDS is a CD4 count below
200 cells per cubic millimeter (mm^3 ) and/or the
development of an AIDS-defining clinical condi-
tions (an illness that a healthy immune system
would block from occurring).AIDS-DEFINING CLINICAL CONDITIONS
AIDS-associated lymphoma Burkitt’s lymphoma
CANDIDIASIS chronicHERPES SIMPLEX
COCCIDIOIDOMYCOSIS CRYPTOCOCCOSIS
CRYPTOSPORIDIOSIS CYTOMEGALOVIRUS(CMV)
HISTOPLASMOSIS disease or retinitis
HIV-related ENCEPHALOPATHY invasive CERVICAL CANCER
isosporiasis KAPOSI’S SARCOMA
Mycobacterium avium Pneumocystis carinii
complex PNEUMONIA
progressive multifocal SalmonellaSEPTICEMIA,
leukoencephalopathy recurrent
TOXOPLASMOSISof brain TUBERCULOSIS
wasting syndrome due to HIVTreatment Options and Outlook
There are numerous treatment protocols for
HIV/AIDS that extend both life expectancy and
QUALITY OF LIFE. Early HIV infection does not
require treatment beyond lifestyle measures to
stay as healthy as possible. As the HIV begins to334 Infectious Diseases