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Home > Wellness > Health Library > HIV (Human Immunodeficiency Virus) Infection
immunodeficiency virus) is a virus that attacks the
immune system, the body's natural defense system.
Without a strong immune system, the body has trouble fighting off disease. Both
the virus and the infection it causes are called HIV.
White blood cells are an important part of the immune system. HIV infects and
destroys certain white blood cells called CD4+ cells. If too many CD4+ cells
are destroyed, the body can no longer defend itself against infection.
The last stage of HIV infection is
AIDS (acquired immunodeficiency syndrome). People with
AIDS have a low number of CD4+ cells and get infections or cancers that rarely
occur in healthy people. These can be deadly.
But having HIV doesn't mean you have AIDS. Even without treatment, it takes a long time for HIV to
progress to AIDS—usually 10 to 12 years.
When HIV is diagnosed before it becomes
AIDS, medicines can slow or stop the damage to the immune system. If AIDS does develop, medicines can often help the immune system return to a healthier state.
treatment, many people with HIV are able to live long and active lives.
There are two types of
HIV infection is caused by the
human immunodeficiency virus. You can get HIV from contact with infected blood,
semen, or vaginal fluids.
HIV doesn't survive well outside the body. So it can't
be spread by casual contact like kissing or sharing drinking glasses with an
HIV may not cause symptoms
early on. People who do have symptoms may mistake them for the
mono. Common early symptoms include:
Symptoms may appear from a few days to several weeks
after a person is first infected. The early symptoms usually go away within 2
to 3 weeks.
After the early symptoms go away, an infected person
may not have symptoms again for many years. After a certain
point, symptoms reappear and then remain. These symptoms usually
A doctor may suspect HIV if symptoms last and no
other cause can be found.
have been exposed to HIV, your immune system will make antibodies to try to
destroy the virus. Doctors use tests to find these antibodies in urine, saliva, or blood.
If a test on urine or saliva shows that you are infected
with HIV, you will probably have a blood test to confirm the results.
Most doctors use two blood tests, called the ELISA and the Western blot. If the first ELISA is positive (meaning that HIV antibodies are found),
the blood sample is tested again. If the second test is positive, a Western blot will be done to be sure.
It may take as long as 6 months
for HIV antibodies to show up in your blood. If you think you have been
exposed to HIV but you test negative for it:
You can get HIV testing in most
doctors' offices, public health clinics, hospitals, and Planned Parenthood
clinics. You can also buy a home HIV test kit in a drugstore or by mail order. Make sure it's one that is approved by the Food and Drug Administration (FDA). If a home test is positive, see a doctor to
have the result confirmed and to find out what to do next.
The standard treatment for HIV
is a combination of medicines called antiretroviral therapy, or ART. Antiretroviral medicines slow the rate at which the virus multiplies.
Taking these medicines can reduce the amount of virus in your body and help you
Medical experts recommend that people begin treatment for HIV as soon as they know that they are infected.1, 2
monitor the HIV infection and its effect on your immune system, a doctor will
regularly do two tests:
After you start treatment, it's important to take your medicines exactly
as directed by your doctor. When treatment doesn't work, it is often because
HIV has become
resistant to the medicine. This can happen if you
don't take your medicines correctly.
HIV is often spread by people who don't know they have it. So it's always important to protect yourself and others by taking these steps:
You also can take antiretroviral medicine to help protect yourself from HIV infection. But to keep your risk low, you still need to practice safer sex even while you are taking the medicine.
Learning about HIV:
Living with HIV:
Health Tools help you make wise health decisions or take action to improve your health.
The HIV infection is caused by the
human immunodeficiency virus (HIV).
HIV is in the body, it starts to destroy CD4+ cells, which are white blood cells that help the body fight infection and disease.
HIV is spread when blood,
semen, or vaginal fluids from an infected person enter
another person's body, usually through sexual contact, from sharing needles
when injecting drugs, or from mother to baby during birth.
HIV may not cause symptoms
early on. People who do have symptoms may mistake them for the
mono. Early symptoms of HIV are called acute retroviral syndrome. The symptoms may include:
These first symptoms can range from mild to severe and
usually disappear on their own after 2 to 3 weeks. But many people don't have symptoms or they have such mild symptoms that they don't notice them at this stage.
After the early symptoms go away, an infected person
may not have symptoms again for many years. After a certain
point, symptoms reappear and then remain.
Untreated HIV infection progresses in
stages. These stages are based on your symptoms and
the amount of the virus in your blood.
Later symptoms may include:
HIV may be suspected when a woman has at least one
of the following:
Children who have HIV often have
different symptoms (for example, delayed growth or an
spleen) than teens or adults.
HIV is spread when
semen, or vaginal fluids from an infected person enter
another person's body, usually through:
HIV may be spread more easily
in the early
stage of infection and again
later, when symptoms of HIV-related illness develop.
A woman who is infected
with HIV can spread the virus to her baby during pregnancy, delivery, or
The virus doesn't survive well outside the body. So HIV cannot be spread through casual contact with an infected person, such as
by sharing drinking glasses, by casual kissing, or by coming into contact with the person's sweat or urine.
It is now extremely rare in the United States for HIV to
be transmitted by
blood transfusions or organ transplants.
After you've been infected, it can take 2 weeks to 6 months for your body to start making HIV antibodies.
This means that during this time you could have a negative HIV test, even though you have been infected and can spread the virus to others.
This is commonly
called the "window period," or
Most people go through the following
stages after being infected with HIV:
The first stage of HIV infection is defined by the U.S. Centers for Disease Control and Prevention (CDC) as a CD4+ cell count of at least 500 cells per microliter or a percentage of CD4+ cells at least 29% of all
lymphocytes. People in this stage don't have any symptoms.3
The second stage of HIV infection is defined by the CDC as a CD4+ cell count of 200
to 499 or a percentage of CD4+ cells of 14% to 28%.3 It may take years for HIV symptoms
to develop during this stage. But even though no symptoms are present, the virus is making copies of itself (multiplying) in the body during this time.
HIV multiplies so
quickly that the
immune system can't destroy the virus. After years of
fighting HIV, the immune system starts to weaken.
AIDS occurs when the CD4+ cell counts drop below 200, the percentage of CD4+ cells is less than 14%, or an AIDS-defining condition is present.4
If HIV isn't treated, most people get
AIDS within 10 to 12 years after the initial infection.
With treatment for HIV, the progression to AIDS may be delayed or
After your immune system starts to weaken, you are
more likely to get certain infections or illnesses, called
opportunistic infections. Examples include some types
pneumonia or cancer that are more common when you have
weakened immune system.
A small number of people who are infected with HIV are
rapid progressors. They develop AIDS within a few years if they don't get treatment. It is not known why the infection progresses faster in these
untreated, AIDS is often fatal within 18 to 24 months after it develops. Death
may occur sooner in people who
rapidly progress through the stages of HIV or in young
A few people have
HIV that doesn't progress to more severe symptoms or disease. They are
referred to as
A small number of people
never become infected with HIV despite years of exposure to the virus. These
people are said to be
You have an
increased risk of becoming infected with HIV through sexual contact if
People who inject drugs or steroids, especially if they
share needles, syringes, cookers, or other equipment used to inject drugs, are
at risk of being infected with HIV.
Babies who are born to mothers
who are infected with HIV are also at risk of infection.
Most children younger than 13 years who have
HIV were infected with the virus by their mothers.
If you are infected with
HIV or caring for someone who is, call 911 or other emergency services immediately if any of the following conditions
Call your doctor if any of the following conditions
Call your doctor to find out
whether HIV testing is needed if you suspect you have been exposed to HIV,
particularly if you engage in
high-risk behavior and have any of the following
If you have not been tested for HIV, call your doctor
Getting tested for HIV can be scary, but the condition
can be managed with treatment. So it is important to get tested if you think you have been
If you don't have symptoms of HIV even though you have
tested positive for the virus, you and your doctor may simply keep watching
for symptoms to occur.
If you don't show any signs of disease and your CD4+
cell count is more than 500 cells per microliter (mcL), you may not need
treatment. But during this time you still need regular checkups with a doctor
to monitor the amount of
HIV in your blood and see how well your immune system is working.
Health professionals who can diagnose and may treat
HIV can also be diagnosed and treated at an HIV care
Complications of HIV may require treatment by the
clinics and other organizations may provide free or low-cost, confidential testing and
counseling about HIV and high-risk behavior.
If you don't have a doctor, contact one of the following for information
on HIV testing in your area:
To prepare for your appointment, see the topic Making the Most of Your Appointment.
The U.S. Centers for Disease Control and
Prevention (CDC) recommends that all people should get tested for HIV as part of
their regular medical care.
United States Preventive Services Task Force (USPSTF)
recommends HIV testing:5
You and your doctor can decide if testing is right for you.
Some people are afraid to be tested for HIV. But if there
is any chance you could be infected, it is very important to find out. HIV can
be treated. Getting early treatment can slow down the virus and help you stay
healthy. And you need to know if you are infected so you can prevent spreading
the infection to other people.
Your doctor may recommend counseling before and after HIV testing. It
is usually available at the hospital or clinic where you will be tested. This
will give you an opportunity to:
positive for HIV will probably make you anxious and afraid about your future.
depression are common reactions.
Don't be afraid to ask for the emotional support you need. If your family and
friends aren't able to provide you with support, a
professional counselor can help.
The good news is that people being treated for HIV are living longer than ever
before with the help of medicines that can often prevent AIDS from developing. Your doctor can help you understand
your condition and how best to treat it.
HIV is diagnosed when
antibodies to HIV are found in the blood. The two
main blood tests are:
HIV is diagnosed only after two or more positive ELISA tests are confirmed by one positive Western blot assay. These tests usually can be done on the same blood sample.
ELISA test results usually come back in 2 to 4 days.
Results of the Western blot take 1 to 2 weeks.
Rapid antibody tests are available that give results right away. One rapid blood test can detect both HIV antibodies and antigens, which allows an HIV infection to be found earlier than was possible in the past. Positive results of a rapid test may need to be confirmed by the ELISA or Western blot test.
Until you know the results of your test:
A home test kit for HIV (called OraQuick) has been approved by the U.S. Food and Drug Administration (FDA). For the test, you rub your gums with a swab supplied by the kit. Then you place the swab into a vial of liquid. The test strip on the swab indicates if you have HIV or not.
Another type of test kit for HIV is a home blood test kit. This type of
kit provides instructions and materials for collecting a small blood sample by sticking your finger with a lancet. The blood is placed onto a special card that is
then sent to a lab for analysis. You get the results over the phone using an
anonymous code number. Counseling is also available over the phone for people
who use the test kit.
If the results from a home test kit show that you have an HIV infection, talk with a doctor.
If you test positive, your doctor will complete a
medical history and physical exam.
He or she may order
several lab tests to check your overall health, including:
Other tests may be done to check for current or past infections that may become worse because of HIV. You may be tested for:
When you have HIV, two tests
are done regularly to see how much of the virus is in your blood (viral load) and how the virus is affecting your
The results of these tests may help
you make decisions about starting
switching to new medicines if the ones you are taking aren't helping.
HIV often changes or
mutates in the body. Sometimes these changes make the virus resistant to certain medicines. Then the medicine no
Medical experts recommend testing the blood of everyone diagnosed with HIV to look for this drug resistance.6 This information helps
your doctor know what medicines to use.
also may be tested for drug resistance when:
AIDS is the
last and most severe stage of HIV infection. It is diagnosed if the results of
your test show that you have:
The most effective treatment for
antiretroviral therapy (ART), a
combination of several medicines that aims to control the amount
of virus in your body. For more information, see Medications.
Other steps you can take include the following:
Medical experts recommend that people begin treatment for HIV as soon as they know that they are infected.1, 2 Treatment is especially important for pregnant women, people who have other infections (such as tuberculosis or hepatitis), and people who have symptoms of AIDS.
Research suggests that
treatment of early HIV with antiretroviral medicines has long-term
benefits, such as a stronger immune system.6
But you may decide not to get treated at first. If you put off treatment, you will still need regular checkups to measure the amount of
HIV in your blood and check how well your immune system is working.
You may want to start HIV treatment if your sex partner doesn't have HIV. Treatment of your HIV infection can help prevent the spread of HIV to your sex partner.6
Health care workers
who are at risk for HIV because of an accidental needlestick or other
exposure to body fluids should get medicine to prevent infection.7
Also, medicine may prevent HIV infection in a person who
has been raped or was accidentally exposed to the body fluids of a person who
may have HIV.8 This type of treatment is usually
started within 72 hours of the exposure.
And studies have shown that if you are not infected with HIV, taking antiretroviral medicines can protect you against HIV.9, 10, 11 But to keep your risk low, you still need to use safer sex practices.
Learning how to live with HIV infection may keep
your immune system strong, while also preventing the spread of HIV to
If your partner has
HIV progresses to a late stage,
treatment will be started or continued to keep your immune system as healthy as possible.
If you get any diseases that point to AIDS, such as Pneumocystis pneumonia or Kaposi's sarcoma, your doctor will treat them.
Many important end-of-life decisions can be made while
you are active and able to communicate your wishes. For more information, see
Care at the End of Life.
Practice safer sex. This includes using a
condom unless you are in a
relationship with one partner who does not have HIV or other sex
If you do have sex with someone who has HIV, it is
important to practice safer sex and to be regularly tested for
Talk with your sex partner or partners about their sexual
history as well as your own sexual history. Find out whether your partner has a history of behaviors that increase his or her risk for HIV.
You may be able to take a combination medicine (tenofovir plus emtricitabine) every day to help prevent infection with HIV. This medicine can lower the risk of getting HIV.9, 10, 11 But the medicine is expensive, and you still need to practice safer sex to keep your risk low.
If you use alcohol or drugs, be very careful. Being under the influence can make you careless about practicing safer sex.
And never share
intravenous (IV) needles, syringes, cookers, cotton,
cocaine spoons, or eyedroppers with others if you use drugs.
If you are infected with HIV, you can greatly lower the risk of spreading the infection to your sex partner by starting treatment when your immune system is still healthy.
Experts recommend starting treatment as soon as you know you are infected.1
A large study found that early treatment greatly lowers the risk of spreading HIV to an uninfected partner.12 This study was done mainly with heterosexual couples, so the effectiveness of HIV treatment in preventing the spread of HIV to a same-sex partner may be different.
If you are HIV-positive (infected with HIV) or have engaged
in sex or needle-sharing with someone who could be infected with HIV, take
precautions to avoid spreading the infection to others.
The risk of a woman spreading HIV to her baby can be
greatly reduced if she:
The baby should also receive
treatment after it is born.
If you are infected with
HIV, you can lead an active life for a long time.
Support groups are often good places to share information, problem-solving tips, and emotions related to HIV infection.
You may be able to find a support group by searching the Internet. Or you can ask your doctor to help you find one.
immunizations and the medicine treatment you need to prevent certain
infections or illnesses, such as some types of
pneumonia or cancer that are more likely to develop in
people who have a weakened immune system.
A skilled caregiver can provide the
emotional, physical, and medical care that will improve the quality of life for
a person who has HIV.
If your partner has HIV:
Medicines used to treat HIV are called antiretrovirals. Several of
these are combined for treatment called
antiretroviral therapy, or ART.
When choosing medicines, your doctor will
Medicines for HIV may have unpleasant side effects. They may sometimes make you feel worse than you
did before you started taking them. Talk to your doctor about your side
effects. He or she may be able to adjust your medicines or prescribe a
You may be able to take several medicines combined
into one pill. This reduces the number of pills you have to take each
Resistance to HIV medicines can occur when:
antiretroviral therapy (ART) reduces your risk of developing
resistance to HIV medicines.
If your viral load doesn't
drop as expected, or if your CD4+ cell count starts to fall, your doctor will
try to find out why the treatment didn't work.
two main reasons that treatment fails:
Counseling may help you to:
Reducing stress can help you
better manage the HIV illness. Some methods of stress reduction include:
Marijuana has been shown to stimulate the appetite and relieve nausea. Talk to your doctor if you're interested in trying it.
complementary treatments for HIV need to be carefully
Some people with HIV may use these types of treatment to help with
fatigue and weight loss caused by HIV infection and reduce the side effects
caused by antiretroviral therapy (ART).
Some complementary therapies for other problems may actually
be harmful. For example,
St. John's wort decreases the effectiveness of certain prescription
medicines for HIV.
Make sure to discuss complementary therapies with your
doctor before trying them.
U.S. Department of Health and
Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2012). Guidelines for the Use of Antiretroviral Agents
in HIV-1-Infected Adults and Adolescents. Available online: http://aidsinfo.nih.gov/contentfiles/lvguidelines/adultandadolescentgl.pdf.
Thompson MA, et al. (2012). Antiretroviral treatment of adult HIV infection: 2012 recommendations of the International Antiviral Society—USA Panel. JAMA, 308(4): 387–402.
Schneider E, et al. (2008). Revised surveillance case
definitions for HIV infection among adults, adolescents, and children aged <
18 months and for HIV infection and AIDS among children aged 18 months to <
13 years—United States, 2008. MMWR, 57(RR-10): 1–12.
Also available online: http://www.cdc.gov/mmwr/PDF/rr/rr5710.pdf.
U.S. Centers for Disease Control and Prevention (1992). 1993 Revised classification system for HIV infection
and expanded surveillance case definition for AIDS among adolescents and adults. MMWR, 41(RR-17):
U.S. Preventive Services Task Force (2013). Screening for HIV: U.S. Preventive Services Task Force
recommendation statement. Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspshivi.htm.
U.S. Department of Health and Human Services Panel on Antiretroviral Guidelines for Adults and Adolescents (2011). Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Available online: http://www.aidsinfo.nih.gov/ContentFiles/AdultandAdolescentGL.pdf.
Kuhar DT, et al. (2013). Updated U.S. Public Health Service Guidelines for the management of occupational exposures to human immunodeficiency virus and recommendations for postexposure prophylaxis. Infection Control and Hospital Epidemiology, 34(9): 875–892.
Centers for Disease Control and Prevention (2005). Antiretroviral postexposure prophylaxis after sexual, injection-drug use, or other nonoccupational exposure to HIV in the United States. Recommendations from the U.S. Department of Health and Human Services. Available online: http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5402a1.htm.
Grant RM, et al. (2010). Preexposure chemoprophylaxis for HIV prevention
in men who have sex with men. New England Journal of Medicine, 363(27): 2588–2599.
Baeten JM, et al. (2012). Antiretroviral prophylaxis for HIV prevention in heterosexual men and women. New England Journal of Medicine, 367(5): 399–410.
Thigpen MC, et al. (2012). Antiretroviral preexposure prophylaxis for
heterosexual HIV transmission in Botswana. New England Journal of Medicine, 367(5): 423–434.
Cohen MS, et al. (2011). Prevention of HIV-1 infection with early
antiretroviral therapy. New England Journal of Medicine, July 18, epub ahead of print (doi:10.1056/NEJMoa1105243).
Lazzaretti RK, et al. (2012). Dietary intervention prevents dyslipidemia associated with highly active antiretroviral therapy in human immunodeficiency virus type 1-infected individuals: A randomized trial. Journal of the American College of Cardiology, 59(11): 979–988.
Triant VA, et al. (2007). Increased acute myocardial
infarction rates and cardiovascular risk factors among patients with HIV
disease. Journal of Clinical Endocrinology and Metabolism. Available online:
http://jcem.endojournals.org/cgi/rapidpdf/jc.2006-2190v1 (e-pub ahead of
Chaturvedi AK, et al. (2007). Elevated risk of lung
cancer among people with AIDS. AIDS, 21(2):
Other Works Consulted
Aberg JA, et al. (2009). Primary care guidelines for the management of persons infected with HIV: 2009 update by the HIV Medicine Association of the Infectious Diseases Society of America. Clinical Infectious Diseases, 49(5): 651–681.
American College of Obstetricians and Gynecologists
(2008, reaffirmed 2011). Prenatal and perinatal human immunodeficiency virus testing: Expanded
recommendations. ACOG Committee Opinion No. 418. Obstetrics and Gynecology, 112(3): 739–742.
Antiretroviral Therapy Cohort Collaboration (2003).
Prognostic importance of initial response in HIV-1 infected patients starting
potent antiretroviral therapy: Analysis of prospective studies. Lancet, 362(9385): 679–686.
Del Rio C, Curran JW (2010). Epidemiology and
prevention of acquired immunodeficiency syndrome and human inmmunodeficiency
virus infection. In GL Mandell et al., eds., Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 7th ed.,
vol. 1, pp. 1635–1661. Philadelphia: Churchill Livingstone Elsevier.
Eron JJ Jr, Hirsch MS (2008). Antiviral therapy of
human immunodeficiency virus infection. In KK Holmes et al., eds.,
Sexually Transmitted Diseases, 4th ed., pp. 1393–1421.
New York: McGraw-Hill.
Jia Z, et al. (2012). Antiretroviral therapy to prevent HIV transmission in serodiscordant couples in China (2003–11): A national observational cohort study. Lancet. Published online November 30, 2012 (doi:10.1016/S0140-6736(12)61898-4).
Kitahata MM, et al. (2009). Effect of early versus
deferred antiretroviral therapy for HIV on survival. New England Journal of Medicine. Published online April 1, 2009
Mocroft A, et al. (2003). Decline in AIDS and death
rates in the EuroSIDA study: An observational study. Lancet, 362(9377): 22–29.
Rerks-Ngarm S, et al. (2009). Vaccination with ALVAC and AIDSVAX to prevent HIV-1 infection in Thailand. New England Journal of Medicine, 361(23): 2209–2220.
Thompson MA, et al. (2010). Antiretroviral treatment of adult HIV infection: 2010 Recommendations of the International AIDS Society—USA Panel. Journal of the American Medical Society, 304(3): 321–333.
U.S. Centers for Disease Control and Prevention (2009). Guidelines for prevention and treatment of opportunistic infections in HIV-infected adults and adolescents: Recommendations from CDC, the National Institutes of Health, and the HIV Medicine Association of the Infectious Diseases Society of America. MMWR, 58(Early Release): 1–207.
World Health Organization (2010). Antiretroviral drugs for treating pregnant women and preventing HIV infection in infants: Recommendations for a public health approach, 2010 version. Available online: http://www.who.int/hiv/pub/mtct/antiretroviral2010/en/index.html.
World Health Organization (2010). Antiretroviral therapy for HIV infection in adults and adolescents: Recommendations for a public health approach. Available online: http://whqlibdoc.who.int/publications/2010/9789241599764_eng.pdf.
World Health Organization (2010). Antiretroviral therapy for HIV infection in infants and children: Towards universal access. Available online: http://whqlibdoc.who.int/publications/2010/9789241599801_eng.pdf.
World Health Organization (2010). Guidelines on HIV and infant feeding 2010: Principles and recommendations
for infant feeding in
the context of HIV
and a summary
of evidence. Available online: http://whqlibdoc.who.int/publications/2010/9789241599535_eng.pdf.
November 6, 2013
E. Gregory Thompson, MD - Internal Medicine & Peter Shalit, MD, PhD - Internal Medicine
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