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HIV
What is HIV?
HIV (human immunodeficiency virus) is the virus that causes AIDS. This
virus is passed from one person to another through blood-to-blood and
sexual contact. In addition, infected pregnant women can pass HIV to their
baby during pregnancy or delivery, as well as through breast-feeding.
People with HIV have what is called HIV infection. Most of these people
will develop AIDS as a result of their HIV infection.
These body fluids have been proven to
spread HIV:
- Blood
- Semen
- Vaginal fluid
- Breast milk
- other body fluids containing blood
These are additional body fluids that may
transmit the virus that health care workers may come into contact with:
- Cerebrospinal fluid surrounding the
brain and the spinal cord
- Synovial fluid surrounding bone joints
- Amniotic fluid surrounding a fetus
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Where did HIV come
from?
Findings
presented at the 6th Conference on Retroviruses and Opportunistic
Infections held in Chicago from January 31 to February 4, 1999, provide
the strongest evidence to date that HIV-1 originated in non-human
primates, probably chimpanzees. Researchers from the University of Alabama
at Birmingham presented evidence identifying a new isolate of a retrovirus
affecting a chimpanzee subspecies (Pan troglodytes and showed that this
and other chimpanzees isolates are related to the different groups of
HIV-1 affecting humans. According to Dr. Hahn and colleagues, the
establishment of HIV-1 in humans is likely to have resulted from
cross-species transmission.
This new knowledge can lead to a better
understanding of the evolution of HIV-1, provide insight into
species-to-species transmission of viruses, and increase our understanding
of infectious disease emergence. Deeper understanding of strain evolution
could in the longer term be of relevance to the development of diagnostic
assays and vaccines.
Two types of HIV have been identified to
date: HIV-1 and HIV-2.
HIV-1 is the predominant HIV type in the
United States and throughout the world. HIV-2 is primarily found in West
Africa.
The origin of HIV-2 has been identified as
being another monkey species, the sooty mangabey (Cercocebus atys); Dr.
Hahn also played a key role in that research.
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Symptoms
What are the symptoms?: - The only way to determine for sure whether you
are infected is to be tested for HIV infection. You cannot rely on
symptoms to know whether or not you are infected with HIV. Many people who
are infected with HIV do not have any symptoms at all for many years.
The following may be warning signs of
infection with HIV:
- Rapid weight loss
- Dry cough
- Recurring fever or profuse night sweats
- Profound and unexplained fatigue
- Swollen lymph glands in the armpits,
groin, or neck
- Diarrhoea that lasts for more than a
week
- White spots or unusual blemishes on the
tongue, in the mouth, or in the throat
- Pneumonia
- Red, brown, pink, or purplish blotches
on or under the skin or inside the mouth, nose, or eyelids
- Memory loss, depression, and other
neurological disorders
However, no one should assume they are
infected if they have any of these symptoms. Each of these symptoms can be
related to other illnesses. Again, the only way to determine whether you
are infected is to be tested for HIV infection.
Similarly, you cannot rely on symptoms to
establish that a person has AIDS. The symptoms of AIDS are similar to the
symptoms of many other illnesses. AIDS is a medical diagnosis made by a
doctor based on specific criteria established by the CDC.
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Can HIV survive in ground water, sewage,
body fluids, and corpses of HIV-infected persons?
The CDC has received
many inquiries concerning the survival of HIV in ground water, sewage,
body fluids, and corpses of HIV-infected persons. Most of the questions
posed assume that HIV can be transmitted in the environment; however, this
type of transmission has not been documented. The overwhelming scientific
evidence is that HIV is fragile and highly susceptible to physical and
chemical agents and therefore does not survive well outside the human
body.
An extensive study on the survival of HIV
after drying was reported by Resnik and coworkers (Stability and
inactivation of HTLV-III/LAV under clinical and laboratory environments.
Journal of the American Medical Association 1986;255:1887-91). The purpose
of the study was to determine the inactivation rate of HIV under
experimental conditions - an objective that required the use of extremely
high levels of HIV. The concentrations studied were at least 100,000 times
greater than those typically found in the blood of HIV-infected persons.
It is not surprising that when such high concentrations of HIV were used,
the virus could be detected 1 to 3 days after drying. Upon close
examination of these data and from other results that have been obtained
by CDC, however, it is clear that drying causes a rapid (within 1 or 2
hours) reduction in virus concentration and renders 90 to 99 percent of
the virus inactive.
Other studies have shown that HIV is
rapidly inactivated by a range of physical and chemical agents such as low
levels of heat, pH extremes, and a variety of chemicals. These
observations, coupled with the enormous dilution factors in sewage
systems, suggest that on-the-job HIV risk factors for sewage workers are
virtually nonexistent. HIV is transmitted by sexual contact with an
infected person, perinatally from an infected woman to her fetus or
infant, through needle-sharing among intravenous drug users, and rarely,
from accidents involving needlestick injuries and other blood exposures of
health-care providers. Because there is no epidemiologic or laboratory
evidence that HIV can be transmitted by the fecal-oral route or by air,
fears associated with HIV transmission by other types of contact with
sewage are not warranted.
Although there have been no specific
studies of HIV survival in corpses before or after embalming, no instances
of HIV transmission have been reported from an exposure incurred in
performing mortuary services. The chemical germicides in embalming fluids
have been tested and found to completely inactivate HIV. CDC has also
published occupational infection control guidelines that apply to mortuary
workers, including embalmers.
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How does temperature effect the survival of
HIV?
HIV is very fragile and does not survive well outside the human
body. HIV is inactivated by heat and dies after 30 minutes at 56EC
(132.8EF). It is also highly susceptible to physical and chemical agents.
If properly stored, HIV is very stable at
low temperatures. It can last 7-10 days at 4EC (39.2EF) and months to
years at -70EC (-94EF). The Centers for Disease Control and Prevention
(CDC) stores purified virus preparations in liquid nitrogen (-200EC or
-328EF). In all cases, the stability of HIV depends on the presence of the
proper concentration
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