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| 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 (US Center for Disease Control)..
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.
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| HIV in the Environment
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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 setting "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.
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| 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.
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| 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. |
| HIV/AIDS Symptoms |
Many people do
not develop symptoms after getting infected with
HIV. Some people have a flu-like illness within
several days to weeks after exposure to the virus.
They complain of fever, headache, tiredness, and
enlarged lymph glands in the neck. These symptoms
usually disappear on their own within a few weeks.
- Following initial infection, you may have
no symptoms. The progression of disease varies
widely among individuals. This state may last
from a few months to more than 10 years.
- During this period, the virus continues
to multiply actively and infects and kills
the cells of the immune system. The immune
system allows us to fight against the bacteria,
viruses, and other infectious causes.
- The virus destroys the cells that are
the primary infection fighters, called CD4+
or T4 cells.
- Once the immune system weakens, a person
infected with HIV can develop the following
symptoms:
- Lack of energy
- Weight loss
- Frequent fevers and sweats
- Persistent or frequent yeast infections
- Persistent skin rashes or flaky skin
- Short-term memory loss
- Mouth, genital, or anal sores from herpes
infections.
- AIDS is the most advanced stage of HIV infection.
The definition of AIDS includes all HIV-infected
people who have fewer than 200 CD4+ cells per
microliter of blood. The definition also includes
26 conditions that are common in advanced HIV
disease but that rarely occur in healthy people.
Most of these conditions are infections caused
by bacteria, viruses, fungi, parasites, and
other organisms. Opportunistic infections are
common in people with AIDS. Nearly every organ
system is affected. Some of the common symptoms
include the following:
- Cough and shortness of breath
- Seizures and lack of coordination
- Difficult or painful swallowing
- Mental symptoms such as confusion and
forgetfulness
- Severe and persistent diarrhea
- Fever
- Vision loss
- Nausea, abdominal cramps, and vomiting
- Weight loss and extreme fatigue
- Severe headaches with neck stiffness
- Coma
- People with AIDS are prone to develop various
cancers such as Kaposi sarcoma, cervical cancer,
and cancers of the immune system known as lymphomas.
Kaposi sarcoma causes round, brown, reddish
or purple spots that develop in the skin or
in the mouth. After the diagnosis of AIDS is
made, the average survival time has been estimated
to be 2-3 years.
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| Effectiveness of
Condoms |
Condoms are classified
as medical devices and are regulated by the Food
and Drug Administration (FDA). Condom manufacturers
in the United States test each latex condom for
defects, including holes, before it is packaged.
The proper and consistent use of latex or polyurethane
(a type of plastic) condoms when engaging in sexual
intercourse--vaginal, anal, or oral--can greatly
reduce a person’s risk of acquiring or transmitting
sexually transmitted diseases, including HIV infection.
There are many different types and brands of condoms
available--however, only latex or polyurethane condoms
provide a highly effective mechanical barrier to
HIV. In laboratories, viruses occasionally have
been shown to pass through natural membrane ("skin"
or lambskin) condoms, which may contain natural
pores and are therefore not recommended for disease
prevention (they are documented to be effective
for contraception). Women may wish to consider using
the female condom when a male condom cannot be used.
s For condoms to provide maximum protection, they
must be used consistently (every time) and correctly.
Several studies of correct and consistent condom
use clearly show that latex condom breakage rates
in this country are less than 2 percent. Even when
condoms do break, one study showed that more than
half of such breaks occurred prior to ejaculation.
When condoms are used reliably, they have been shown
to prevent pregnancy up to 98 percent of the time
among couples using them as their only method of
contraception. Similarly, numerous studies among
sexually active people have demonstrated that a
properly used latex condom provides a high degree
of protection against a variety of sexually transmitted
diseases, including HIV infection.
For more detailed information about condoms, see
the CDC publication "Facts about Condoms and
Their Use in Preventing HIV Infection and Other
STDs."
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| Source: US Center
for Disease Control and eMedicineHealth.com |
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