AIDS
Introduction: Acquired immunodeficiency
syndrome (HIV/AIDS) is caused by a retrovirus, called
the AIDS virus or human immunodeficiency virus (+HIV). Two types have sofar been
found, HIV-1 and HIV-2.The more common and more aggressive type is HIV-1, which
is found all over the world. HIV-2 is found mainly in West Africa and some countries
that have close ties to it. Both cause the same clinical disease picture, but
HIV-1 seems to progress faster to the clinical stage. There are some misconceptions
about infectiousness. For instance, viral hepatitis is much more infectious
than HIV. We know this from health care workers who were accidentally injured
by a contaminated needle or contaminated instruments. The rate of lab certified
seroconversion in the health care workers was only 0.5% in documented HIV cases,
but was 25% if the blood came from patients who had documented viral hepatitis.
The most infectious mode of transmission comes from blood to blood contact. The
most dangerous situation is if there is unprotected sex with a person who has
a concurrent chancroid ulcer (another sexually transmitted disease). In this
setting there is a weak immune system of the donor with AIDS with high numbers
of circulating HIV viruses, which leak freely from a chancroid as this person
engages in sexual activity. In the case of homosexual sex, where the recipient
is exposed to the virus load via the rectum, there is the added risk by the fact
that rectal mucosa is extremely fragile and leads to open microulcers that will
readily accept the virus directly into the blood stream. With heterosexual sex
transmission of the HIV virus into the female recipient is not as easy because
the vaginal mucosa is built stronger than rectal mucosa. On the other hand, if
there are chancroid ulcers in the vagina transmission rates will be higher. A
lot of knowledge has been accumulated since the early 1980's when the AIDS epidemic
hit North America and the rest of the world. Here are some of the findings (Ref.
2, p. 3).
| Although the AIDS virus
is sometimes found in saliva, urine, tears and bronchial secretions, transmission
from these secretions has not been reported. | Biting
insects do not seem to transmit AIDS from person to person. |
| 15% to 35% of infants get AIDS from their mothers
just before, during or shortly after birth. | | About
50% of infants of AIDS positive mothers get it from breast feeding. |
| The main mode of transmission of AIDS is through
risky sexual behavior: sexual intercourse with overlapping partners or with multiple
concurrent partners or with a partner who is infected with AIDS. |
| Oral sex has a low transmission
rate, homosexual sex has a high rate. | | Contaminated
needles shared among drug addicts is another form of transmission. |
| Incubation time from the time of
exposure to detectable infection is 1 to 3 months. |
HIV infects the cell mediated immune system, particularly the T lymphocytes
called "T helper cells" (or "CD4+ cells", formerly termed
"T4 cells"). They are the helper cells assisting in antibody formation
of the immune system, but also are the main T cells that initiate a cell mediated
immune response to viral and fungal infectious diseases. There seem to
be several stages in the development of AIDS over time. There is the initial infection
and it takes about 1 to 3 months before antibodies can be detected (before the
AIDS test gets positive). However, during this initial phase the infectiousness
is high as the immune system is paralyzed and the virus is rapidly multiplying.
A slow invisible incubation phase ensues, where the patient feels well initially
and it takes between 1 and 10 years before clinical signs of AIDS develop. Without
treatment AIDS then develops clinically and is recognizable by one or several
"opportunistic" infections (candidiasis,tuberculosis, Cryptococcus etc.)
that take place or by the development of malignancies such as Kaposi's sarcoma
or non-Hodgkins lymphoma. The common denominator is that now the immune system
is profoundly weakened to the point where all these infections or tumors can develop.
With the newer treatments since the 1990's (particularly the addition of protease
inhibitors) it is now possible to help AIDS patients to live a more normal life.
Nevertheless, there are many unanswered questions and future research hopefully
will shed more light on these and lead to new solutions. | |
