Acquired immune deficiency syndrome or
acquired immunodeficiency syndrome
(
AIDS) is a disease of the human
immune system caused by the
human immunodeficiency virus (HIV).
This condition progressively reduces the effectiveness of the
immune system and leaves individuals susceptible to
opportunistic infections and
tumors. HIV is
transmitted through direct contact
of a
mucous membrane or the
bloodstream with a
bodily fluid
containing HIV, such as
blood,
semen,
vaginal fluid,
preseminal fluid, and
breast milk.
This transmission can involve
anal,
vaginal or
oral
sex,
blood transfusion, contaminated
hypodermic needles, exchange between
mother and baby during
pregnancy,
childbirth,
breastfeeding or other exposure to one of the
above bodily fluids.
AIDS is now a
pandemic. In 2007, it was
estimated that 33.2 million people lived with the disease
worldwide, and that AIDS killed an estimated 2.1 million
people, including 330,000 children. Over three-quarters of these
deaths occurred in
sub-Saharan
Africa, retarding
economic
growth and destroying
human
capital.
Genetic research indicates
that HIV originated in west-central Africa during the late
nineteenth or early twentieth century. AIDS was first recognized by
the U.S.
Centers for Disease
Control and Prevention in 1981 and its cause, HIV, identified
in the early 1980s.
Although treatments for AIDS and HIV can slow the course of the
disease, there is currently no
vaccine
or cure.
Antiretroviral
treatment reduces both the
mortality
and the morbidity of HIV infection, but these drugs are expensive
and routine access to antiretroviral
medication is not available in all countries. Due
to the difficulty in treating HIV infection, preventing infection
is a key aim in controlling the AIDS pandemic, with health
organizations promoting
safe sex and
needle-exchange programmes
in attempts to slow the spread of the virus.
Symptoms
[[Image:Hiv-timecourse.png|450px|thumb|right|A generalized graph of
the relationship between HIV copies (viral load) and CD4 counts
over the average course of untreated HIV infection; any particular
individual's disease course may vary considerably.]]
The symptoms of AIDS are primarily the result of conditions that do
not normally develop in individuals with healthy
immune systems. Most of these conditions are
infections caused by
bacteria,
viruses,
fungi and
parasites that are normally controlled by the
elements of the immune system that HIV damages.
Opportunistic infections are
common in people with AIDS. HIV affects nearly every
organ system.
People with AIDS also have an increased risk of developing various
cancers such as
Kaposi's sarcoma,
cervical cancer and cancers of the
immune system known as
lymphomas.
Additionally, people with AIDS often have systemic symptoms of
infection like
fevers,
sweats (particularly at night), swollen
glands, chills, weakness, and
weight
loss. The specific opportunistic infections that AIDS patients
develop depend in part on the prevalence of these infections in the
geographic area in which the patient lives.
Main symptoms of AIDS.
Pulmonary infections
Pneumocystis pneumonia
(originally known as
Pneumocystis carinii pneumonia, and
still abbreviated as PCP, which now stands for
Pneumo
cystis
pneumonia) is relatively rare in healthy,
immunocompetent people, but common among
HIV-infected individuals. It is caused by
Pneumocystis
jirovecii.
Before the advent of effective diagnosis, treatment and routine
prophylaxis in Western countries, it was
a common immediate cause of death. In developing countries, it is
still one of the first indications of AIDS in untested individuals,
although it does not generally occur unless the CD4 count is less
than 200 cells per µL of blood.
Tuberculosis (TB) is unique among
infections associated with HIV because it is transmissible to
immunocompetent people via the respiratory route, is easily
treatable once identified, may occur in early-stage HIV disease,
and is preventable with drug therapy. However,
multidrug resistance is a potentially
serious problem.
Even though its incidence has declined because of the use of
directly observed therapy and other improved practices in Western
countries, this is not the case in developing countries where HIV
is most prevalent. In early-stage HIV infection (CD4 count >300
cells per µL), TB typically presents as a pulmonary disease. In
advanced HIV infection, TB often presents atypically with
extrapulmonary (systemic) disease a common feature. Symptoms are
usually constitutional and are not localized to one particular
site, often affecting
bone marrow,
bone, urinary and
gastrointestinal tracts,
liver, regional
lymph nodes,
and the
central nervous
system.
Gastrointestinal infections
Esophagitis is an inflammation of the
lining of the lower end of the
esophagus
(gullet or swallowing tube leading to the
stomach). In HIV infected individuals, this is
normally due to fungal (
candidiasis) or
viral (
herpes simplex-1 or
cytomegalovirus) infections. In rare
cases, it could be due to
mycobacteria.
Unexplained chronic
diarrhea in HIV
infection is due to many possible causes, including common
bacterial (
Salmonella,
Shigella,
Listeria or
Campylobacter) and parasitic infections;
and uncommon opportunistic infections such as
cryptosporidiosis,
microsporidiosis,
Mycobacterium avium complex (MAC)
and viruses,
astrovirus,
adenovirus,
rotavirus
and
cytomegalovirus, (the latter as
a course of
colitis).
In some cases, diarrhea may be a side effect of several drugs used
to treat HIV, or it may simply accompany HIV infection,
particularly during primary HIV infection. It may also be a side
effect of
antibiotics used to treat
bacterial causes of diarrhea (common for
Clostridium difficile). In the
later stages of HIV infection, diarrhea is thought to be a
reflection of changes in the way the
intestinal tract absorbs nutrients, and may
be an important component of HIV-related
wasting.
Neurological and psychiatric involvement
HIV infection may lead to a variety of neuropsychiatric
sequelae, either by infection of the now susceptible
nervous system by organisms, or as a direct consequence of the
illness itself.
Toxoplasmosis is a disease caused by
the single-celled
parasite called
Toxoplasma gondii; it usually infects the brain, causing
toxoplasma
encephalitis, but it can
also infect and cause disease in the
eyes and
lungs. Cryptococcal meningitis is an infection of the
meninx (the membrane covering the brain and
spinal cord) by the fungus
Cryptococcus neoformans. It can
cause fevers,
headache,
fatigue,
nausea, and
vomiting. Patients may also develop
seizures and confusion; left untreated, it
can be lethal.
Progressive
multifocal leukoencephalopathy (PML) is a
demyelinating disease, in which the
gradual destruction of the
myelin sheath
covering the
axons of nerve cells impairs the
transmission of nerve impulses. It is caused by a virus called
JC virus which occurs in 70% of the
population in
latent form, causing
disease only when the immune system has been severely weakened, as
is the case for AIDS patients. It progresses rapidly, usually
causing death within months of diagnosis.
AIDS dementia complex (ADC) is
a metabolic
encephalopathy induced by
HIV infection and fueled by immune activation of HIV infected brain
macrophages and
microglia. These cells are productively infected
by HIV and secrete
neurotoxins of both
host and viral origin. Specific neurological impairments are
manifested by cognitive, behavioral, and motor abnormalities that
occur after years of HIV infection and are associated with low
CD4
+ T cell levels and high plasma viral loads.
Prevalence is 10–20% in Western countries but only 1–2% of HIV
infections in India. This difference is possibly due to the HIV
subtype in India. AIDS related mania is sometimes seen in patients
with advanced HIV illness; it presents with more irritability and
cognitive impairment and less euphoria than a
manic episode associated with true
bipolar disorder. Unlike the latter
condition, it may have a more chronic course. This syndrome is less
often seen with the advent of multi-drug therapy.
Tumors and malignancies
Patients with HIV infection have substantially increased incidence
of several
cancers. This is primarily due to
co-infection with an
oncogenic DNA virus, especially
Epstein-Barr virus (EBV),
Kaposi's
sarcoma-associated herpesvirus (KSHV) (also known as human
herpesvirus-8 [HHV-8]), and human
papillomavirus (HPV).
Kaposi's sarcoma (KS) is the most common tumor in HIV-infected
patients. The appearance of this tumor in young homosexual men in
1981 was one of the first signals of the AIDS epidemic. Caused by a
gammaherpes virus called
Kaposi's
sarcoma-associated herpes virus (KSHV), it often appears as
purplish
nodules on the skin, but
can affect other organs, especially the
mouth,
gastrointestinal tract, and lungs. High-grade
B
cell lymphomas such as
Burkitt's lymphoma, Burkitt's-like
lymphoma, diffuse large B-cell lymphoma (DLBCL), and
primary central nervous
system lymphoma present more often in HIV-infected patients.
These particular cancers often foreshadow a poor prognosis.
Epstein-Barr virus (EBV) or KSHV
cause many of these lymphomas. In HIV-infected patients, lymphoma
often arises in extranodal sites such as the gastrointestinal
tract. When they occur in an HIV-infected patient, KS and
aggressive B cell lymphomas confer a diagnosis of AIDS.
Invasive
cervical cancer in
HIV-infected women is also considered AIDS-defining. It is caused
by
human papillomavirus
(HPV).
In addition to the AIDS-defining tumors listed above, HIV-infected
patients are at increased risk of certain other tumors, notably
Hodgkin's disease,
anal and
rectal
carcinomas,
hepatocellular
carcinomas,
head and neck
cancers, and
lung cancer. Some of
these are causes by viruses, such as Hodgkin's disease (EBV),
anal/rectal cancers (HPV), head and neck cancers (HPV), and
hepatocellular carcinoma (hepatitis B or C). Other contributing
factors include exposure to carcinogens (cigarette smoke for lung
cancer), or living for years with subtle immune defects.
Interestingly, the incidence of many common tumors, such as
breast cancer or
colon cancer, does not increase in HIV-infected
patients. In areas where
HAART is extensively
used to treat AIDS, the incidence of many AIDS-related malignancies
has decreased, but at the same time malignant cancers overall have
become the most common cause of death of HIV-infected patients. In
recent years, an increasing proportion of these deaths have been
from non-AIDS-defining cancers.
Other infections
AIDS patients often develop opportunistic infections that present
with non-specific symptoms, especially
low-grade fevers and weight loss. These
include opportunistic infection with
Mycobacterium avium-intracellulare
and
cytomegalovirus (CMV). CMV can
cause colitis, as described above, and
CMV retinitis can cause
blindness.
Penicilliosis due to
Penicillium marneffei is now the
third most common opportunistic infection (after extrapulmonary
tuberculosis and
cryptococcosis) in
HIV-positive individuals within the endemic area of
Southeast Asia.
An infection that often goes unrecognized in AIDS patients is
Parvovirus B19. Its main consequence
is anemia, which is difficult to distinguish from the effects of
antiretroviral drugs used to treat AIDS itself.
Cause
AIDS is the most severe acceleration of
infection with HIV. HIV is a
retrovirus that primarily infects vital organs of
the human
immune system such as
CD4+ T cells (a subset of
T cells),
macrophages and
dendritic cells. It directly and indirectly
destroys CD4
+ T cells.
Once HIV has killed so many CD4
+ T cells that there are
fewer than 200 of these cells per
microliter (µL) of
blood,
cellular immunity is lost.
Acute HIV infection progresses over
time to clinical latent HIV infection and then to early
symptomatic HIV infection and later to AIDS,
which is identified either on the basis of the amount of
CD4
+ T cells remaining in the blood, and/or the presence
of certain infections, as noted above.
In the absence of
antiretroviral
therapy, the
median time of progression from HIV
infection to AIDS is nine to ten years, and the median survival
time after developing AIDS is only 9.2 months. However, the rate of
clinical disease progression varies widely between individuals,
from two weeks up to 20 years.
Many factors affect the rate of progression. These include factors
that influence the body's ability to defend against HIV such as the
infected person's general immune function. Older people have weaker
immune systems, and therefore have a greater risk of rapid disease
progression than younger people.
Poor access to
health care and the
existence of coexisting infections such as
tuberculosis also may predispose people to
faster disease progression. The infected person's
genetic inheritance plays an important role and
some people are
resistant to
certain strains of HIV. An example of this is people with the
homozygous CCR5-Δ32 variation are resistant to infection
with certain
strains of HIV. HIV is
genetically variable and exists as different strains, which cause
different rates of clinical disease progression.
Sexual transmission
Sexual transmission occurs with the contact between sexual
secretions of one person with the rectal, genital or oral
mucous membranes of another. Unprotected
receptive sexual acts are riskier than unprotected insertive sexual
acts, and the risk for transmitting HIV through unprotected anal
intercourse is greater than the risk from vaginal intercourse or
oral sex.
However, oral sex is not entirely safe, as HIV can be transmitted
through both insertive and receptive oral sex.
Sexual assault greatly increases the risk of
HIV transmission as condoms are rarely employed and physical trauma
to the vagina or rectum occurs frequently, facilitating the
transmission of HIV.
Other
sexually
transmitted infections (STI) increase the risk of HIV
transmission and infection, because they cause the disruption of
the normal
epithelial barrier by
genital ulceration and/or microulceration; and
by accumulation of pools of HIV-susceptible or HIV-infected cells
(
lymphocytes and
macrophages) in semen and vaginal secretions.
Epidemiological studies from sub-Saharan Africa,
Europe and
North America
suggest that genital ulcers, such as those caused by
syphilis and/or
chancroid,
increase the risk of becoming infected with HIV by about fourfold.
There is also a significant although lesser increase in risk from
STIs such as
gonorrhea,
chlamydia and
trichomoniasis, which all cause local
accumulations of lymphocytes and macrophages.
Transmission of HIV depends on the infectiousness of the
index case and the susceptibility of the
uninfected partner. Infectivity seems to vary during the course of
illness and is not constant between individuals. An undetectable
plasma
viral load does not necessarily
indicate a low viral load in the seminal liquid or genital
secretions.
However, each 10-fold increase in the level of HIV in the blood is
associated with an 81% increased rate of HIV transmission. Women
are more susceptible to HIV-1 infection due to hormonal changes,
vaginal microbial ecology and physiology, and a higher prevalence
of sexually transmitted diseases.
People who have been infected with one strain of HIV can still be
infected later on in their lives by other, more
virulent strains.
Infection is unlikely in a single encounter. High rates of
infection have been linked to a pattern of overlapping long-term
sexual relationships. This allows the virus to quickly spread to
multiple partners who in turn infect their partners. A pattern of
serial monogamy or occasional casual encounters is associated with
lower rates of infection.
HIV spreads readily through heterosexual sex in Africa, but less so
elsewhere. One possibility being researched is that
schistosomiasis, which affects up to 50 per
cent of women in parts of Africa, damages the lining of the
vagina.
Exposure to blood-borne pathogens
CDC poster from 1989 highlighting the
threat of AIDS associated with drug use
This transmission route is particularly relevant to
intravenous drug users,
hemophiliacs and recipients of
blood transfusions and blood products.
Sharing and reusing
syringes contaminated
with HIV-infected blood represents a major risk for infection with
HIV.
Needle sharing is the cause of one third of all new HIV-infections
in
North America, China, and
Eastern Europe. The risk of being infected
with HIV from a single prick with a needle that has been used on an
HIV-infected person is thought to be about 1 in 150 (
see table above).
Post-exposure prophylaxis with
anti-HIV drugs can further reduce this risk.
This route can also affect people who give and receive
tattoos and
piercings.
Universal precautions are
frequently not followed in both sub-Saharan Africa and much of Asia
because of both a shortage of supplies and inadequate
training.
The
WHO estimates that approximately 2.5% of all
HIV infections in sub-Saharan Africa are transmitted through unsafe
healthcare injections. Because of this, the
United Nations General
Assembly has urged the nations of the world to implement
precautions to prevent HIV transmission by health workers.
The risk of transmitting HIV to
blood
transfusion recipients is extremely low in developed countries
where improved donor selection and HIV screening is performed.
However, according to the
WHO, the overwhelming majority of
the world's population does not have access to safe blood and
between 5% and 10% of the world's HIV infections come from
transfusion of infected blood and blood products.
Perinatal transmission
The transmission of the virus from the mother to the child can
occur
in utero during the last
weeks of pregnancy and at childbirth. In the absence of treatment,
the transmission rate between a mother and her child during
pregnancy, labor and delivery is 25%.
However, when the mother takes antiretroviral therapy and gives
birth by
caesarean section, the
rate of transmission is just 1%. The risk of infection is
influenced by the viral load of the mother at birth, with the
higher the viral load, the higher the risk.
Breastfeeding also increases the risk of
transmission by about 4 %.
Misconceptions
A number of misconceptions have arisen surrounding HIV/AIDS. Three
of the most common are that AIDS can spread through casual contact,
that sexual intercourse with a virgin will cure AIDS, and that HIV
can infect only homosexual men and drug users. Other misconceptions
are that any act of anal intercourse between gay men can lead to
AIDS infection, and that open discussion of homosexuality and HIV
in schools will lead to increased rates of homosexuality and
AIDS.
Pathophysiology
The pathophysiology of AIDS is complex, as is the case with all
syndromes. Ultimately, HIV causes AIDS by
depleting CD4
+ T helper lymphocytes. This weakens the
immune system and allows
opportunistic infections. T
lymphocytes are essential to the immune response and without them,
the body cannot fight infections or kill cancerous cells. The
mechanism of CD4
+ T cell depletion differs in the acute
and chronic phases.
During the acute phase, HIV-induced cell lysis and killing of
infected cells by
cytotoxic T
cells accounts for CD4
+ T cell depletion, although
apoptosis may also be a factor. During the
chronic phase, the consequences of generalized immune activation
coupled with the gradual loss of the ability of the immune system
to generate new T cells appear to account for the slow decline in
CD4
+ T cell numbers.
Although the symptoms of immune deficiency characteristic of AIDS
do not appear for years after a person is infected, the bulk of
CD4
+ T cell loss occurs during the first weeks of
infection, especially in the intestinal mucosa, which harbors the
majority of the lymphocytes found in the body. The reason for the
preferential loss of mucosal CD4
+ T cells is that a
majority of mucosal CD4
+ T cells express the CCR5
coreceptor, whereas a small fraction of CD4
+ T cells in
the bloodstream do so.
HIV seeks out and destroys CCR5 expressing CD4
+ cells
during acute infection. A vigorous immune response eventually
controls the infection and initiates the clinically latent phase.
However, CD4
+ T cells in mucosal tissues remain depleted
throughout the infection, although enough remain to initially ward
off life-threatening infections.
Continuous HIV replication results in a state of generalized immune
activation persisting throughout the chronic phase. Immune
activation, which is reflected by the increased activation state of
immune cells and release of proinflammatory
cytokines, results from the activity of several
HIV gene products and the immune response to ongoing HIV
replication. Another cause is the breakdown of the immune
surveillance system of the mucosal barrier caused by the depletion
of mucosal CD4
+ T cells during the acute phase of
disease.
This results in the systemic exposure of the immune system to
microbial components of the gut’s normal flora, which in a healthy
person is kept in check by the mucosal immune system. The
activation and proliferation of T cells that results from immune
activation provides fresh targets for HIV infection. However,
direct killing by HIV alone cannot account for the observed
depletion of CD4
+ T cells since only 0.01–0.10% of
CD4
+ T cells in the blood are infected.
A major cause of CD4
+ T cell loss appears to result from
their heightened susceptibility to apoptosis when the immune system
remains activated. Although new T cells are continuously produced
by the
thymus to replace the ones lost, the
regenerative capacity of the thymus is slowly destroyed by direct
infection of its
thymocytes by HIV.
Eventually, the minimal number of CD4
+ T cells necessary
to maintain a sufficient immune response is lost, leading to
AIDS
Cells affected
The
virus, entering through which ever route,
acts primarily on the following cells:
The effect
The
virus has
cytopathic effects but how it does it is
still not quite clear. It can remain inactive in these cells for
long periods, though. This effect is hypothesized to be due to the
CD
4-gp120 interaction.
- The most prominent effect of HIV is its T-helper cell
suppression and lysis. The cell is simply killed off or deranged to
the point of being function-less (they do not respond to foreign
antigens). The infected B-cells can not
produce enough antibodies either. Thus the immune system collapses
leading to the familiar AIDS complications, like infections and
neoplasms (vide supra).
- Infection of the cells of the CNS cause acute aseptic meningitis, subacute encephalitis, vacuolar myelopathy and peripheral neuropathy. Later it leads
to even AIDS dementia complex.
- The CD4-gp120 interaction (see above) is also
permissive to other viruses like Cytomegalovirus, Hepatitis virus, Herpes simplex virus, etc. These viruses lead
to further cell damage i.e. cytopathy.
Molecular basis
For details, see:
Diagnosis
The diagnosis of AIDS in a person infected with HIV is based on the
presence of certain signs or symptoms. Since June 5, 1981, many
definitions have been developed for
epidemiological surveillance such as the
Bangui definition and the
1994
expanded World Health Organization AIDS case definition.
However, clinical staging of patients was not an intended use for
these systems as they are neither sensitive, nor specific. In
developing countries, the
World Health Organization staging
system for HIV infection and disease, using clinical and laboratory
data, is used and in developed countries, the
Centers for Disease
Control (CDC) Classification System is used.
WHO disease staging system
In 1990, the
World Health
Organization (WHO) grouped these infections and conditions
together by introducing a staging system for patients infected with
HIV-1. An update took place in September 2005. Most of these
conditions are
opportunistic
infections that are easily treatable in healthy people.
CDC classification system
There are two main definitions for AIDS, both produced by the
Centers for
Disease Control and Prevention (CDC). The older definition is
to referring to AIDS using the diseases that were associated with
it, for example,
lymphadenopathy,
the disease after which the discoverers of HIV originally named the
virus. In 1993, the CDC expanded their definition of AIDS to
include all HIV positive people with a CD4
+ T cell count
below 200 per µL of blood or 14% of all
lymphocytes. The majority of new AIDS cases in
developed countries use either
this definition or the pre-1993 CDC definition. The AIDS diagnosis
still stands even if, after treatment, the CD4
+ T cell
count rises to above 200 per µL of blood or other AIDS-defining
illnesses are cured.
HIV test
Many people are unaware that they are infected with HIV. Less than
1% of the sexually active urban population in Africa has been
tested, and this proportion is even lower in rural populations.
Furthermore, only 0.5% of pregnant women attending urban health
facilities are counseled, tested or receive their test results.
Again, this proportion is even lower in rural health facilities.
Therefore,
donor blood and blood
products used in medicine and medical research are screened for
HIV.
HIV tests are usually performed on venous blood. Many laboratories
use
fourth generation screening tests which detect
anti-HIV antibody (IgG and IgM) and the HIV p24 antigen. The
detection of HIV antibody or antigen in a patient previously known
to be negative is evidence of HIV infection. Individuals whose
first specimen indicates evidence of HIV infection will have a
repeat test on a second blood sample to confirm the results.
The
window period (the time between
initial infection and the development of detectable antibodies
against the infection) can vary since it can take 3–6 months
to
seroconvert and to test positive.
Detection of the virus using polymerase chain reaction (
PCR) during the window period is possible, and evidence
suggests that an infection may often be detected earlier than when
using a fourth generation EIA screening test.
Positive results obtained by PCR are confirmed by antibody
tests.Routinely used HIV tests for infection in
neonates and
infants (ie,
patients younger than 2 years), born to HIV-positive mothers, have
no value because of the presence of maternal antibody to HIV in the
child's blood. HIV infection can only be diagnosed by PCR, testing
for HIV pro-viral DNA in the children's
lymphocytes.
Prevention
Estimated per act risk for acquisition
of HIV by exposure route
|
| Exposure Route |
Estimated
infections
per 10,000 exposures
to an infected source |
| Blood Transfusion |
9,000 |
| Childbirth (to
child) |
2,500 |
| Needle-sharing injection drug use |
67 |
| Percutaneous needle stick |
30 |
| Receptive anal
intercourse* |
50 |
| Insertive anal
intercourse* |
6.5 |
| Receptive penile-vaginal
intercourse* |
10 |
| Insertive penile-vaginal
intercourse* |
5 |
| Receptive oral
intercourse*§ |
1 |
| Insertive oral
intercourse*§ |
0.5 |
* assuming no
condom use
§ source refers to oral intercourse
performed on a man |
The three main transmission routes of HIV are
sexual contact, exposure to infected body
fluids or tissues, and from mother to
fetus or
child during
perinatal period. It is
possible to find HIV in the
saliva,
tears, and
urine of infected
individuals, but there are no recorded cases of infection by these
secretions, and the risk of infection is negligible.
Sexual contact
The majority of HIV infections are acquired through
unprotected sex relations between partners,
one of whom has HIV. The primary mode of HIV infection worldwide is
through sexual contact between members of the opposite sex.
During a sexual act, only male or female
condoms can reduce the chances of infection with HIV
and other STDs and the chances of becoming
pregnant. The best evidence to date indicates that
typical condom use reduces the risk of
heterosexual HIV transmission by approximately
80% over the long-term, though the benefit is likely to be higher
if condoms are used correctly on every occasion.
The male
latex condom, if used correctly
without oil-based lubricants, is the single most effective
available technology to reduce the sexual transmission of HIV and
other sexually transmitted infections. Manufacturers recommend that
oil-based lubricants such as
petroleum
jelly, butter, and
lard not be used with
latex condoms, because they dissolve the
latex, making the condoms
porous. If necessary, manufacturers recommend using
water-based lubricants.
Oil-based lubricants can however be used with
polyurethane condoms.
The
female condom is an alternative to
the male condom and is made from
polyurethane, which allows it to be used in the
presence of oil-based lubricants. They are larger than male condoms
and have a stiffened ring-shaped opening, and are designed to be
inserted into the vagina.
The female condom contains an inner ring, which keeps the condom in
place inside the vagina – inserting the female condom requires
squeezing this ring. However, at present availability of female
condoms is very low and the price remains prohibitive for many
women.
Preliminary studies suggest that, where female condoms are
available, overall protected sexual acts increase relative to
unprotected sexual acts, making them an important HIV prevention
strategy.
Studies on couples where one partner is infected show that with
consistent condom use, HIV infection rates for the uninfected
partner are below 1% per year. Prevention strategies are well-known
in developed countries, but epidemiological and behavioral studies
in Europe and North America suggest that a substantial minority of
young people continue to engage in high-risk practices despite
HIV/AIDS knowledge, underestimating their own risk of becoming
infected with HIV.
Randomized controlled
trials have shown that male
circumcision lowers the risk of HIV infection
among heterosexual men by up to 60%. It is expected that this
procedure will be actively promoted in many of the countries
affected by HIV, although doing so will involve confronting a
number of practical, cultural and attitudinal issues. However,
programs to encourage condom use, including providing them free to
those in poverty, are estimated to be 95 times more cost effective
than circumcision at reducing the rate of HIV in sub-Saharan
Africa.
Some experts fear that a lower perception of vulnerability among
circumcised men may result in more sexual risk-taking behavior,
thus negating its preventive effects. However, one randomized
controlled trial indicated that adult male circumcision was not
associated with increased HIV risk behavior.
Exposure to infected body fluids
Health care workers can reduce exposure to HIV by employing
precautions to reduce the risk of exposure to contaminated blood.
These precautions include barriers such as gloves, masks,
protective eyeware or shields, and gowns or aprons which prevent
exposure of the skin or mucous membranes to blood borne pathogens.
Frequent and thorough washing of the skin immediately after being
contaminated with blood or other bodily fluids can reduce the
chance of infection. Finally, sharp objects like needles, scalpels
and glass, are carefully disposed of to prevent needlestick
injuries with contaminated items. Since intravenous drug use is an
important factor in HIV transmission in developed countries,
harm reduction strategies such as
needle-exchange programmes
are used in attempts to reduce the infections caused by drug
abuse.
Mother-to-child transmission (MTCT)
Current recommendations state that when replacement feeding is
acceptable, feasible, affordable, sustainable and safe,
HIV-infected mothers should avoid breast-feeding their infant.
However, if this is not the case, exclusive breast-feeding is
recommended during the first months of life and discontinued as
soon as possible. It should be noted that women may breastfeed
other children who are not their own; see
wetnurse.
Treatment
- See also HIV Treatment and
Antiretroviral drug.
The chemical structure of Abacavir
There is currently no publicly available
vaccine for HIV or cure for
HIV or AIDS. The only known methods of prevention are
based on avoiding exposure to the virus or, failing that, an
antiretroviral treatment directly after a highly significant
exposure, called
post-exposure
prophylaxis (PEP). PEP has a very demanding four week schedule
of dosage. It also has very unpleasant side effects including
diarrhea,
malaise,
nausea and
fatigue.
Antiviral therapy
Current treatment for HIV infection consists of
highly active
antiretroviral therapy, or HAART. This has been highly
beneficial to many HIV-infected individuals since its introduction
in 1996 when the protease inhibitor-based HAART initially became
available. Current optimal HAART options consist of combinations
(or "cocktails") consisting of at least three drugs belonging to at
least two types, or "classes," of
antiretroviral agents. Typical regimens
consist of two
nucleoside
analogue reverse transcriptase inhibitors (NARTIs or NRTIs)
plus either a
protease
inhibitor or a
non-nucleoside
reverse transcriptase inhibitor (NNRTI). Because HIV disease
progression in children is more rapid than in adults, and
laboratory parameters are less predictive of risk for disease
progression, particularly for young infants, treatment
recommendations are more aggressive for children than for adults.
In developed countries where HAART is available, doctors assess the
viral load, rapidity in CD4 decline, and
patient readiness while deciding when to recommend initiating
treatment.
Standard goals of HAART include improvement in the patient’s
quality of life, reduction in complications, and reduction of HIV
viremia below the limit of detection, but it does not cure the
patient of HIV nor does it prevent the return, once treatment is
stopped, of high blood levels of HIV, often HAART resistant.
Moreover, it would take more than the lifetime of an individual to
be cleared of HIV infection using HAART. Despite this, many
HIV-infected individuals have experienced remarkable improvements
in their general health and quality of life, which has led to the
plummeting of HIV-associated morbidity and mortality. In the
absence of HAART, progression from HIV infection to AIDS occurs at
a
median of between nine to ten years and the
median survival time after developing AIDS is only 9.2 months.
HAART is thought to increase survival time by between 4 and
12 years.
For some patients, which can be more than fifty percent of
patients, HAART achieves far less than optimal results, due to
medication intolerance/side effects, prior ineffective
antiretroviral therapy and infection with a drug-resistant strain
of HIV. Non-adherence and non-persistence with therapy are the
major reasons why some people do not benefit from HAART. The
reasons for non-adherence and non-persistence are varied. Major
psychosocial issues include poor access to medical care, inadequate
social supports, psychiatric disease and drug abuse. HAART regimens
can also be complex and thus hard to follow, with large numbers of
pills taken frequently. Side effects can also deter people from
persisting with HAART, these include
lipodystrophy,
dyslipidaemia,
diarrhoea,
insulin
resistance, an increase in
cardiovascular risks and
birth defects. Anti-retroviral drugs are
expensive, and the majority of the world's infected individuals do
not have access to medications and treatments for HIV and
AIDS.
Experimental and proposed treatments
It has been postulated that only a vaccine can halt the pandemic
because a vaccine would possibly cost less, thus being affordable
for developing countries, and would not require daily treatments.
However, even after almost 30 years of research, HIV-1 remains
a difficult target for a vaccine.
Research to improve current treatments includes decreasing side
effects of current drugs, further simplifying drug regimens to
improve adherence, and determining the best sequence of regimens to
manage drug resistance. A number of studies have shown that
measures to prevent opportunistic infections can be beneficial when
treating patients with HIV infection or AIDS.
Vaccination against
hepatitis A and B is advised for patients who are
not infected with these viruses and are at risk of becoming
infected. Patients with substantial immunosuppression are also
advised to receive prophylactic therapy for
Pneumocystis jiroveci
pneumonia (PCP), and many patients may benefit from
prophylactic therapy for
toxoplasmosis
and
Cryptococcus meningitis as well.
Researchers have discovered an
abzyme that
can destroy the protein
gp120 CD4 binding
site. This protein is common to all HIV variants as it is the
attachment point for
B lymphocytes and
subsequent compromising of the immune system.
In
Berlin
, Germany
, a
42-year-old leukemia patient infected with
HIV for more than a decade was given an experimental transplant of bone marrow with
cells that contained an unusual natural variant of the CCR5 cell-surface receptor. This
CCR5-Δ32 variant has been shown to make
some cells from people who are born with it resistant to infection
with some strains of HIV. Almost two years after the transplant,
and even after the patient reportedly stopped taking antiretroviral
medications, HIV has not been detected in the patient's
blood.
Alternative medicine
Various forms of
alternative
medicine have been used to treat symptoms or alter the course
of the disease. Current studies indicate that alternative medicine
therapies have little effect on the mortality or morbidity of the
disease, but may improve the quality of life of individuals with
AIDS. The psychological benefits of these therapies are the most
important use.
Acupuncture has been used
to alleviate some symptoms with no success and cannot cure the HIV
infection. Several randomized clinical trials testing the effect of
herbal medicines have shown that there is no evidence that these
herbs have any effect on the progression of the disease, but may
instead produce serious side-effects.
Morbidity and mortality among HIV-infected adults with adequate
dietary nutritional intake is unaffected by
multivitamin supplementation. A large Tanzanian
trial in immunologically and nutritionally compromised pregnant and
lactating women showed a number of benefits to daily multivitamin
supplementation for both mothers and children. Dietary intake of
micronutrients at
RDA
levels by HIV-infected adults is recommended by the
World Health Organization. There
is some evidence that
vitamin A
supplementation in children reduces mortality and improves growth.
Daily doses of
selenium can suppress HIV
viral burden with an associated improvement of the CD4 count.
Selenium can be used as an adjunct therapy to standard antiviral
treatments, but cannot itself reduce mortality and morbidity.
Prognosis
Without treatment, the net median survival time after infection
with HIV is estimated to be 9 to 11 years, depending on the HIV
subtype, and the median survival rate after diagnosis of AIDS in
resource-limited settings where treatment is not available ranges
between 6 and 19 months, depending on the study. In areas where it
is widely available, the development of
HAART
as effective therapy for HIV infection and AIDS reduced the death
rate from this disease by 80%, and raised the life expectancy for a
newly diagnosed HIV-infected person to about 20 years.
As new treatments continue to be developed and because HIV
continues to
evolve resistance to
treatments, estimates of survival time are likely to continue to
change. Without antiretroviral therapy, death normally occurs
within a year. Most patients die from opportunistic infections or
malignancies associated with the
progressive failure of the immune system. The rate of clinical
disease progression varies widely between individuals and has been
shown to be affected by many factors such as host susceptibility
and immune function health care and co-infections, as well as which
particular strain of the virus is involved.
Even with anti-retroviral treatment, over the long term
HIV-infected patients may experience
neurocognitive disorders,
osteoporosis,
neuropathy,
cancers,
nephropathy, and
cardiovascular disease. It is not
always clear whether these conditions result from the infection,
related complications, or are side effects of treatment.
Epidemiology
Estimated prevalence of HIV among
young adults (15–49) per country at the end of 2005
The AIDS pandemic can also be seen as several epidemics of separate
subtypes; the major factors in its spread are sexual transmission
and vertical transmission from mother to child at birth and through
breast milk. Despite recent, improved access to antiretroviral
treatment and care in many regions of the world, the AIDS pandemic
claimed an estimated 2.1 million (range 1.9–2.4 million)
lives in 2007 of which an estimated 330,000 were children under
15 years.Globally, an estimated 33.2 million people lived
with HIV in 2007, including 2.5 million children. An estimated
2.5 million (range 1.8–4.1 million) people were newly infected
in 2007, including 420,000 children.
Sub-Saharan Africa
remains by far the worst affected region. In 2007 it contained an
estimated 68% of all people living with AIDS and 76% of all AIDS
deaths, with 1.7 million new infections bringing the number of
people living with HIV to 22.5 million, and with
11.4 million AIDS orphans living in the region. Unlike other
regions, most people living with HIV in sub-Saharan Africa in 2007
(61%) were women. Adult
prevalence in
2007 was an estimated 5.0%, and AIDS continued to be the single
largest cause of mortality in this region.
South Africa has the largest population of HIV
patients in the world, followed by Nigeria
and
India. South & South East
Asia are second worst affected; in 2007 this region contained
an estimated 18% of all people living with AIDS, and an estimated
300,000 deaths from AIDS. India has an estimated 2.5 million
infections and an estimated adult prevalence of 0.36%.
Life expectancy has fallen dramatically in
the worst-affected countries; for example, in 2006 it was estimated
that it had dropped from 65 to 35 years in Botswana
.
In the United States, young African-American women are also at
unusually high risk for HIV infection. This is due in part to a
lack of information about AIDS and a perception that they are not
vulnerable, as well as to limited access to health-care resources
and a higher likelihood of sexual contact with at-risk male sexual
partners. There are also geographic disparities in AIDS prevalence
in the United States, where it is most common in rural areas and in
the southern states, particularly in the Appalachian and
Mississippi Delta regions and along the border with Mexico.
History
AIDS was first reported June 5, 1981, when the U.S.
Centers for Disease
Control recorded a cluster of Pneumocystis carinii
pneumonia (now still classified as PCP but known to be caused
by Pneumocystis
jirovecii) in five homosexual men in Los
Angeles
. In the beginning, the CDC did not have an
official name for the disease, often referring to it by way of the
diseases that were associated with it, for example,
lymphadenopathy, the disease after which the
discoverers of HIV originally named the virus. They also used
Kaposi's Sarcoma and Opportunistic Infections, the name by
which a task force had been set up in 1981. In the general press,
the term
GRID, which stood for
Gay-related immune deficiency,
had been coined.
The CDC, in search of a name, and looking at
the infected communities coined “the 4H disease,” as it seemed to
single out Haitians
, homosexuals, hemophiliacs, and heroin
users. However, after determining that AIDS was not isolated
to the
homosexual community, the term
GRID became misleading and
AIDS was introduced at a
meeting in July 1982. By September 1982 the CDC started using the
name AIDS, and properly defined the illness.
A more controversial theory known as the
OPV AIDS hypothesis suggests that the
AIDS epidemic was inadvertently started in the late 1950s in the
Belgian Congo by
Hilary Koprowski's research into a
poliomyelitis vaccine.According to
scientific consensus, this scenario is
not supported by the available evidence.
A recent
study states that HIV probably moved from Africa to Haiti and then
entered the United States around 1969.
Society and culture
Stigma
AIDS stigma exists around the world in a variety of ways, including
ostracism,
rejection,
discrimination and avoidance of HIV infected
people; compulsory HIV testing without prior
consent or protection of
confidentiality; violence against HIV
infected individuals or people who are perceived to be infected
with HIV; and the
quarantine of HIV
infected individuals. Stigma-related violence or the fear of
violence prevents many people from seeking HIV testing, returning
for their results, or securing treatment, possibly turning what
could be a manageable chronic illness into a death sentence and
perpetuating the spread of HIV.
AIDS stigma has been further divided into the following three
categories:
- Instrumental AIDS stigma—a reflection of the fear and
apprehension that are likely to be associated with any deadly and
transmissible illness.
- Symbolic AIDS stigma—the use of HIV/AIDS to express
attitudes toward the social groups or lifestyles perceived to be
associated with the disease.
- Courtesy AIDS stigma—stigmatization of people
connected to the issue of HIV/AIDS or HIV- positive people.
Often, AIDS stigma is expressed in conjunction with one or more
other stigmas, particularly those associated with
homosexuality,
bisexuality,
promiscuity,
prostitution, and
intravenous drug
use.
In many
developed countries, there
is an association between AIDS and homosexuality or bisexuality,
and this association is correlated with higher levels of sexual
prejudice such as
anti-homosexual
attitudes. There is also a perceived association between AIDS and
all male-male sexual behavior, including sex between uninfected
men.
Economic impact
Changes in life expectancy in some hard-hit African
countries.
HIV and AIDS affects
economic growth
by reducing the availability of
human
capital. Without proper
nutrition,
health care and medicine that is available in developed countries,
large numbers of people suffer and die from AIDS-related
complications. They will not only be unable to work, but will also
require significant medical care. The forecast is that this will
probably cause a collapse of economies and societies in countries
with a significant AIDS population. In some heavily infected areas,
the epidemic has left behind many
orphans
cared for by elderly
grandparents.
The increased mortality in this region will result in a
smaller skilled population and
labor force. This smaller
labor force will be predominantly young people,
with reduced knowledge and
work
experience leading to reduced productivity. An increase in
workers’ time off to look after sick family members or for
sick leave will also lower productivity.
Increased mortality will also weaken the mechanisms that generate
human capital and
investment in people,
through loss of
income and the death of
parents. By killing off mainly young adults, AIDS seriously weakens
the
taxable population, reducing the resources
available for
public expenditures
such as education and health services not related to AIDS resulting
in increasing pressure for the state's finances and slower growth
of the economy. This results in a slower growth of the tax base, an
effect that will be reinforced if there are growing expenditures on
treating the sick, training (to replace sick workers), sick pay and
caring for AIDS orphans. This is especially true if the sharp
increase in adult mortality shifts the responsibility and blame
from the family to the government in caring for these
orphans.
On the level of the household, AIDS results in both the loss of
income and increased spending on healthcare by the household. The
income effects of this lead to spending reduction as well as a
substitution effect away from education and towards healthcare and
funeral spending.
A study in Côte d'Ivoire
showed that households with an HIV/AIDS patient
spent twice as much on medical expenses as other
households.
Religion and AIDS
The topic of religion and AIDS has become highly controversial in
the past twenty years, primarily because many prominent religious
leaders have publicly declared their opposition to the use of
condoms, which scientists feel is currently the only means of
stopping the epidemic. Other issues involve religious participation
in global health care services and collaboration with secular
organizations such as UNAIDS and the World Health
Organization.
AIDS denialism
A small number of activists question the connection between HIV and
AIDS, the existence of HIV, or the validity of current treatment
methods (even going so far as to claim that the drug therapy itself
was the cause of AIDS deaths). Though these claims have been
examined and thoroughly rejected by the
scientific community, they continue to
be promulgated through the
Internet and
have had a significant political impact. In
South Africa, former President
Thabo Mbeki's embrace of AIDS denialism resulted
in an ineffective governmental response to the AIDS epidemic that
has been blamed for hundreds of thousands of AIDS-related
deaths.
See also
Notes and references
- Parasitic worms may boost African HIV
rates
- Agnès-Laurence Chenine, Ela Shai-Kobiler, Lisa N. Steele,
Helena Ong, Peter Augostini, Ruijiang Song, Sandra J. Lee, Patrick
Autissier, Ruth M. Ruprecht, W. Evan Secor Acute Schistosoma mansoni Infection
Increases Susceptibility to Systemic SHIV Clade C Infection in
Rhesus Macaques after Mucosal Virus Exposure PLoS Neglected
Tropical Diseases DOI: 10.1371/journal.pntd.0000265
- Textbook of Pathology by Harsh Mohan, ISBN 81-8061-368-2
- eMedicine - HIV Infection (Pediatrics: General
Medicine)
- AIDS Patients Now Living Longer, But Aging
Faster
- >
- >
- For evidence of the scientific consensus that HIV is the
cause of AIDS, see (for example): * * * * * *
Further reading
External links
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