Aids

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Aids

AIDS - What's new ?
By: Eric Quinley
E-mail: cvcdoc@hotmail.com

AIDS - What's new ? ------------------- Is the message getting through? We already know
enough about AIDS to prevent its spread, but ignorance, complacency, fear and bigotry
continue to stop many from taking adequate precautions. We know enough about how the
infection is transmitted to protect ourselves from it without resorting to such extremes
as mandatory testing, enforced quarantine or total celibacy. But too few people are
heeding the AIDS message. Perhaps many simply don't like or want to believe what they
hear, preferring to think that AIDS "can't happen to them." Experts repeatedly remind us
that infective agents do not discriminate, but can infect any and everyone. Like other
communicable diseases, AIDS can strike anyone. It is not necessarily confined to a few
high-risk groups. We must all protect ourselves from this infection and teach our children
about it in time to take effective precautions. Given the right measures, no one need get
AIDS. The pandemic continues: ----------------------- Many of us have forgotten about the
virulence of widespread epidemics, such as the 1917/18 influenza pandemic which killed
over 21 million people, including 50,000 Canadians. Having been lulled into false security
by modern antibiotics and vaccines about our ability to conquer infections, the Western
world was ill prepared to cope with the advent of AIDS in 1981. (Retro- spective studies
now put the first reported U.S. case of AIDS as far back as 1968.) The arrival of a new
and lethal virus caught us off guard. Research suggests that the agent responsible for
AIDS probably dates from the 1950s, with a chance infection of humans by a modified Simian
virus found in African green monkeys. Whatever its origins, scientists surmise that the
disease spread from Africa to the Caribbean and Europe, then to the U.S. Current estimates
are that 1.5 to 2 million Americans are now probably HIV carriers, with higher numbers in
Central Africa and parts of the Caribbean. Recapping AIDS - the facts:
--------------------------- AIDS is an insidious, often fatal but less contagious disease
than measles, chicken pox or hepatitis B. AIDS is thought to be caused primarily by a
virus that invades white blood cells (lymphocytes) - especially T4-lymphocytes or T-helper
cells - and certain other body cells, including the brain. In 1983 and 1984, French and
U.S. researchers independently identified the virus believed to cause AIDS as an unusual
type of slow-acting retrovirus now called "human immunodeficiency virus" or HIV. Like
other viruses, HIV is basically a tiny package of genes. But being a retrovirus, it has
the rare capacity to copy and insert its genes right into a human cell's own chromo- somes
(DNA). Once inside a human host cell the retrovirus uses its own enzyme, reverse
transcriptase, to copy its genetic code into a DNA molecule which is then incorporated
into the host's DNA. The virus becomes an integral part of the person's body, and is
subject to control mechanisms by which it can be switched "on" or "off". But the viral DNA
may sit hidden and inactive within human cells for years, until some trigger stimulates it
to replicate. Thus HIV may not produce illness until its genes are "turned on" five, ten,
fifteen or perhaps more years after the initial infection. During the latent period, HIV
carriers who harbour the virus without any sign of illness can unknowingly infect others.
On average, the dormant virus seems to be triggered into action three to six years after
first invading human cells. When switched on, viral replication may speed along, producing
new viruses that destroy fresh lymphocytes. As viral replication spreads, the lymphocyte
destruction virtually sabotages the entire immune system. In essence, HIV viruses do not
kill people, they merely render the immune system defenceless against other
"opportunistic: infections, e.g. yeast invasions, toxoplasmosis, cytomegalovirus and
Epstein Barr infections, massive herpes infections, special forms of pneumonia
(Pneumocystis carinii - the killer in half of all AIDS patients), and otherwise rare
malignant tumours (such as Kaposi's sarcoma.) Cofactors may play a crucial contributory
role: ----------------------------------------------- What prompts the dormant viral genes
suddenly to burst into action and start destroying the immune system is one os the central
unsolved challenges about AIDS. Some scientists speculate that HIV replication may be set
off by cofactors or transactivators that stimulate or disturb the immune system. Such
triggers may be genetically determined proteins in someone's system, or foreign substances
from other infecting organisms - such as syphilis, chlamydia, gonorrhea, HTLV-1
(leukemia), herpes, or CMV (cytomegalovirus) - which somehow awaken the HIV virus. The
assumption is that once HIV replication gets going, the lymphocyte destruction cripples
the entire immune system. Recent British research suggest that some people may have a
serum protein that helps them resist HIV while others may have one that makes them
genetically more prone to it by facilitating viral penetration of T-helper cells. Perhaps,
says one expert, everybody exposed to HIV can become infected, but whether or not the
infection progresses to illness depends on multiple immunogenic factors. Some may be lucky
enough to have genes that protect them form AIDS! Variable period until those infected
develop antibodies: -------------------------------------------------------- While HIV
hides within human cells, the body may produce antibodies, but, for reasons not fully
understood, they don't neutralise all the viruses. The presence of HIV antibodies thus
does not confer immunity to AIDS, nor prevent HIV transmission. Carriers may be able to
infect others. The usual time taken to test positive for HIV antibodies after exposure
averages from four to six weeks but can take over a year. Most experts agree that within
six months all but 10 per cent of HIV-infected people "seroconvert" and have detectable
antibodies. While HIV antibody tests can indicate infection, they are not foolproof. The
ELISA is a good screening test that gives a few "false positives" and more "false
negatives" indicating that someone who is infected has not yet developed identifiable
antibodies.) The more specific Western Blot test, done to confirm a positive ELISA, is
very accurate. However, absence of antibodies doesn't guarantee freedom form HIV, as
someone may be in the "window period" when, although already infected, they do not yet
have measurable levels of HIV antibodies. A seropositive result does not mean someone has
AIDS; it means (s)he is carrying antibodies, may be infectious and may develop AIDS at
some future time. As to how long seropositive persons remain infectious, the June 1987
Third International Conference on AIDS was told to assume "FOR LIFE". What awaits
HIV-carriers who test positive?: -------------------------------------------- On this
issue of when those who test HIV positive will get AIDS, experts think that the fast track
to AIDS is about two years after HIV infection; the slow route may be 10, 15, or more
years until symptoms appear. Most specialists agree that it takes at least two years to
show AIDS symptoms after HIV infection, and that within ten years as many as 75 per cent
of those infected may develop AIDS. A report from Atlanta's CDC based on an analysis of
blood collected in San Francisco from 1978 to 1986, showed a steady increase with time in
the rate of AIDS development among HIV-infected persons - 4 percent within three years; 14
percent after five years; 36 percent after seven years. The realistic, albeit doomsday
view is that 100 percent of those who test HIV-positive may eventually develop AIDS. Still
spread primarily by sexual contact: ----------------------------------------- AIDS is
still predominantly a sexually transmitted disease: The other main route of HIV infection
is via contaminated blood and shared IV needles. Since the concentration of virus is
highest in semen and blood, the most common transmission route is from man to man via anal
intercourse, or man to woman via vaginal intercourse. Female HIV carriers can infect male
sex partners. Small amounts of HIV have been isolated from urine, tears, saliva, cereb-
rospinal and amniotic fluid and (some claim) breast milk. But current evidence implicates
only semen, blood, vaginal secretions and possibly breast milk in transmission. Pregnant
mothers can pass the infection to their babies. While breastfeeding is a rare and unproven
transmission route, health officials suggest that seropositive mothers bottle feed their
offspring. AIDS is not confined to male homosexuals and the high risk groups: There are
now reports of heterosexual transmission - form IV drug users, hemo- philiacs or those
infected by blood transfusion to sexual partners. There are a few reported cases of AIDS
heterosexually acquired from a single sexual encounter with a new, unknown mate. And there
are three recent reports of female-to-female (lesbian) transmissions. Spread of AIDS among
drug users alarming: ----------------------------------------- In many cities, e.g. New
York and Edinburgh, where IV drug use is wide- spread, IV drug users often share
blood-contaminated needles. In New York, more than 53 percent of drug users are
HIV-infected and may transmit the infection to the heterosexual population by sexual
contact and transmission from mother to child. Studies in Edinburgh, where 51 percent of
drug users are HIV-infected, show that providing clean needles isn't enough to stem
infection. Even given free disposable needles, many drug abusers preferred the camaraderie
of shared equipment. Only with added teaching programs and free condom offers, are
educational efforts likely to pay off. In New Jersey, offering free treatment coupons plus
AIDS education brought 86 percent of local drug users to classes. A San Francisco program
issued pocket-size containers of chlorine bleach to IVDAs with instructions on how to kill
HIV viruses. The Toronto Addiction Research Foundation notes a similar demand for AIDS
information. Risk of infection via blood transfusion very slight:
---------------------------------------------------- Infection by blood transfusion is
very rare in Canada today. As of November 1985, the Red Cross, which supplies all blood
and blood products to Canadian hospitals, had routinely tested all blood donations for the
HIV antibody. In 1986, when we last discussed AIDS, the Red Cross reported the incidence
of HIV-positive blood samples as 25 in 100,000. Now, at the start of 1988, only 10 per
100,000 blood samples are found to be infected - which, of course, are discarded. Only a
tiny fraction of HIV-positive blood (from HIV-infected people who haven't yet developed
detectable antibodies) can now slip through the Red Cross screening procedure. The minimal
risk is further decreased by screening methods, medical history-taking, questionnaires and
donor inter- views. Very few people at risk of AIDS now come to give blood. The "self-
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