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HIV and Its Transmission
Research has revealed a great deal of valuable
medical, scientific, and public health information
about the human immunodeficiency virus (HIV) and
acquired immunodeficiency syndrome (AIDS). The
ways in which HIV can be transmitted have been
clearly identified. Unfortunately, false information
or statements that are not supported by scientific
findings continue to be shared widely through
the Internet or popular press. Therefore, the
Centers for Disease Control and Prevention (CDC)
has prepared this fact sheet to correct a few
misperceptions about HIV.
How HIV is Transmitted
HIV is spread by sexual contact with an infected
person, by sharing needles and/or syringes (primarily
for drug injection) with someone who is infected,
or, less commonly (and now very rarely in countries
where blood is screened for HIV antibodies), through
transfusions of infected blood or blood clotting
factors. Babies born to HIV-infected women may
become infected before or during birth or through
breast-feeding after birth.
In the health care setting, workers have been
infected with HIV after being stuck with needles
containing HIV-infected blood or, less frequently,
after infected blood gets into a worker’s open
cut or a mucous membrane (for example, the eyes
or inside of the nose). There has been only one
instance of patients being infected by a health
care worker in the United States; this involved
HIV transmission from one infected dentist to
six patients. Investigations have been completed
involving more than 22,000 patients of 63 HIV-infected
physicians, surgeons, and dentists, and no other
cases of this type of transmission have been identified
in the United States.
Some people fear that HIV might be transmitted
in other ways; however, no scientific evidence
to support any of these fears has been found.
If HIV were being transmitted through other routes
(such as through air, water, or insects), the
pattern of reported AIDS cases would be much different
from what has been observed. For example, if mosquitoes
could transmit HIV infection, many more young
children and preadolescents would have been diagnosed
with AIDS.
All reported cases suggesting new or potentially
unknown routes of transmission are thoroughly
investigated by state and local health departments
with the assistance, guidance, and laboratory
support from CDC. No additional routes of transmission
have been recorded, despite a national sentinel
system designed to detect just such an occurrence.
The following paragraphs specifically address
some of the common misperceptions about HIV transmission.
HIV in the Environment
Scientists and medical authorities agree that
HIV does not survive well in the environment,
making the possibility of environmental transmission
remote. HIV is found in varying concentrations
or amounts in blood, semen, vaginal fluid, breast
milk, saliva, and tears. (See page 3, Saliva,
Tears, and Sweat.) To obtain data on the survival
of HIV, laboratory studies have required the use
of artificially high concentrations of laboratory-grown
virus. Although these unnatural concentrations
of HIV can be kept alive for days or even weeks
under precisely controlled and limited laboratory
conditions, CDC studies have shown that drying
of even these high concentrations of HIV reduces
the amount of infectious virus by 90 to 99 percent
within several hours. Since the HIV concentrations
used in laboratory studies are much higher than
those actually found in blood or other specimens,
drying of HIV-infected human blood or other body
fluids reduces the theoretical risk of environmental
transmission to that which has been observed--essentially
zero. Incorrect interpretation of conclusions
drawn from laboratory studies have unnecessarily
alarmed some people.
Results from laboratory studies should not be
used to assess specific personal risk of infection
because (1) the amount of virus studied is not
found in human specimens or elsewhere in nature,
and (2) no one has been identified as infected
with HIV due to contact with an environmental
surface. Additionally, HIV is unable to reproduce
outside its living host (unlike many bacteria
or fungi, which may do so under suitable conditions),
except under laboratory conditions, therefore,
it does not spread or maintain infectiousness
outside its host.
Households
Although HIV has been transmitted between family
members in a household setting, this type of transmission
is very rare. These transmissions are believed
to have resulted from contact between skin or
mucous membranes and infected blood. To prevent
even such rare occurrences, precautions, as described
in previously published guidelines, should be
taken in all settings "including the home"
to prevent exposures to the blood of persons who
are HIV infected, at risk for HIV infection, or
whose infection and risk status are unknown. For
example,
· Gloves should be worn during contact with blood
or other body fluids that could possibly contain
visible blood, such as urine, feces, or vomit.
· Cuts, sores, or breaks on both the care giver’s
and patient’s exposed skin should be covered with
bandages.
· Hands and other parts of the body should be
washed immediately after contact with blood or
other body fluids, and surfaces soiled with blood
should be disinfected appropriately.
· Practices that increase the likelihood of blood
contact, such as sharing of razors and toothbrushes,
should be avoided.
· Needles and other sharp instruments should be
used only when medically necessary and handled
according to recommendations for health-care settings.
(Do not put caps back on needles by hand or remove
needles from syringes. Dispose of needles in puncture-proof
containers out of the reach of children and visitors.)
Businesses and Other Settings
There is no known risk of HIV transmission to
co-workers, clients, or consumers from contact
in industries such as food-service establishments
(see information on survival of HIV in the environment).
Food-service workers known to be infected with
HIV need not be restricted from work unless they
have other infections or illnesses (such as diarrhea
or hepatitis A) for which any food-service worker,
regardless of HIV infection status, should be
restricted. CDC recommends that all food-service
workers follow recommended standards and practices
of good personal hygiene and food sanitation.
In 1985, CDC issued routine precautions that all
personal-service workers (such as hairdressers,
barbers, cosmetologists, and massage therapists)
should follow, even though there is no evidence
of transmission from a personal-service worker
to a client or vice versa. Instruments that are
intended to penetrate the skin (such as tattooing
and acupuncture needles, ear piercing devices)
should be used once and disposed of or thoroughly
cleaned and sterilized. Instruments not intended
to penetrate the skin but which may become contaminated
with blood (for example, razors) should be used
for only one client and disposed of or thoroughly
cleaned and disinfected after each use. Personal-service
workers can use the same cleaning procedures that
are recommended for health care institutions.
CDC knows of no instances of HIV transmission
through tattooing or body piercing, although hepatitis
B virus has been transmitted during some of these
practices. One case of HIV transmission from acupuncture
has been documented. Body piercing (other than
ear piercing) is relatively new in the United
States, and the medical complications for body
piercing appear to be greater than for tattoos.
Healing of piercings generally will take weeks,
and sometimes even months, and the pierced tissue
could conceivably be abraded (torn or cut) or
inflamed even after healing. Therefore, a theoretical
HIV transmission risk does exist if the unhealed
or abraded tissues come into contact with an infected
person’s blood or other infectious body fluid.
Additionally, HIV could be transmitted if instruments
contaminated with blood are not sterilized or
disinfected between clients.
Kissing
Casual contact through closed-mouth or "social"
kissing is not a risk for transmission of HIV.
Because of the potential for contact with blood
during "French" or open-mouth kissing,
CDC recommends against engaging in this activity
with a person known to be infected. However, the
risk of acquiring HIV during open-mouth kissing
is believed to be very low. CDC has investigated
only one case of HIV infection that may be attributed
to contact with blood during open-mouth kissing.
Biting
In 1997, CDC published findings from a state health
department investigation of an incident that suggested
blood-to-blood transmission of HIV by a human
bite. There have been other reports in the medical
literature in which HIV appeared to have been
transmitted by a bite. Severe trauma with extensive
tissue tearing and damage and presence of blood
were reported in each of these instances. Biting
is not a common way of transmitting HIV. In fact,
there are numerous reports of bites that did not
result in HIV infection.
Saliva, Tears, and Sweat
HIV has been found in saliva and tears in very
low quantities from some AIDS patients. It is
important to understand that finding a small amount
of HIV in a body fluid does not necessarily mean
that HIV can be transmitted by that body fluid.
HIV has not been recovered from the sweat of HIV-infected
persons. Contact with saliva, tears, or sweat
has never been shown to result in transmission
of HIV.
Insects
From the onset of the HIV epidemic, there has
been concern about transmission of the virus by
biting and bloodsucking insects. However, studies
conducted by researchers at CDC and elsewhere
have shown no evidence of HIV transmission through
insects--even in areas where there are many cases
of AIDS and large populations of insects such
as mosquitoes. Lack of such outbreaks, despite
intense efforts to detect them, supports the conclusion
that HIV is not transmitted by insects.
The results of experiments and observations of
insect biting behavior indicate that when an insect
bites a person, it does not inject its own or
a previously bitten person’s or animal’s blood
into the next person bitten. Rather, it injects
saliva, which acts as a lubricant or anticoagulant
so the insect can feed efficiently. Such diseases
as yellow fever and malaria are transmitted through
the saliva of specific species of mosquitoes.
However, HIV lives for only a short time inside
an insect and, unlike organisms that are transmitted
via insect bites, HIV does not reproduce (and
does not survive) in insects. Thus, even if the
virus enters a mosquito or another sucking or
biting insect, the insect does not become infected
and cannot transmit HIV to the next human it feeds
on or bites. HIV is not found in insect feces.
There is also no reason to fear that a biting
or bloodsucking insect, such as a mosquito, could
transmit HIV from one person to another through
HIV-infected blood left on its mouth parts. Two
factors serve to explain why this is so--first,
infected people do not have constant, high levels
of HIV in their bloodstreams and, second, insect
mouth parts do not retain large amounts of blood
on their surfaces. Further, scientists who study
insects have determined that biting insects normally
do not travel from one person to the next immediately
after ingesting blood. Rather, they fly to a resting
place to digest this blood meal.
This Information obtained from the Center
for Disease Control
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