Class 12 Biology (India)
What is HIV/AIDS?
You may think that HIV and AIDS are one and the same because they are often talked about in one breath, but that is wrong! Although they are linked, HIV and AIDS are two completely different things, and it’s important to know the difference:
- HIV is a virus that infects humans. It attacks your immune system causing it to malfunction and makes you very ill. HIV stands for human immunodeficiency virus, the virus that causes AIDS.
- AIDS is a serious medical condition comprising of a variety of diseases that occur because HIV interferes with your body’s ability to fight off other infections. AIDS stands for acquired immunodeficiency syndrome.
How HIV affects your body
A virus is a small infectious organism that can only replicate inside living cells of other organisms; in HIV’s case, human immune cells. In order to understand how HIV and AIDS are connected we need to take a closer look at how the immune system works. Your immune system is a complex network of organs, tissues and cells, called white blood cells. The white blood cells are made in the bone marrow, migrate to other parts of the immune system such as the lymph nodes, spleen, and thymus and float around in the bloodstream. The components of your immune system work together to prevent germs from entering, growing and multiplying inside your body.
Image identifying the organs affected by HIV
Your skin is the first line of defense against germs and is a very effective barrier to infection. However, when bacteria, viruses or other germs get past your skin; for example, through a wound, or via your mucous membranes (the soft, moist areas just inside of your nose, mouth, rectum, vagina, or penis), they can enter your bloodstream. If this happens, your white blood cells recognize them as foreign and trigger your immune system to launch a multi-pronged attack that generally eliminates the invaders and prevents a wide scale infection.
Different types of white blood cells are responsible for eliminating different kinds of microorganisms. The group of white blood cells responsible for eliminating viruses and tumor cells are called lymphocytes. There are several different types of lymphocytes, all with different jobs. The ones that are especially relevant to HIV infection are the CD4 lymphocytes or CD4 cells. These cells are a bit like policemen, as they patrol the bloodstream and identify any viruses or tumor cells that shouldn’t be there. If they find something they don’t like the look of, they send out signals that activate other lymphocytes including a group of killer lymphocytes which, as their name suggests, seek out and eliminate the invaders.
Illustration of cells of the immune system
The reason why HIV causes so much trouble when it gets inside your body is because it targets CD4 cells, infects them, multiplies, and fills them with hundreds of new viruses. The new viruses can bud off from the infected cells, but eventually there are so many that the cells burst and die. When this happens, the newly formed viruses are released into the bloodstream where they can infect other uninfected CD4 cells.
Over time, HIV infection causes a massive drop in the total number of CD4 cells from about 1000 cells per microlitre of blood to less than 200 per microlitre, resulting in immunodeficiency. At this point, your immune system is so weak it can no longer fight off other germs when they enter your body, making you extremely susceptible to infections and cancers that would not usually occur. The onset of these opportunistic infections is the beginning of what we call AIDS.
How is HIV diagnosed?
You only know for sure that you have HIV if you get tested. The most common HIV test is a blood test. Your doctor will take a small sample and send it off to a laboratory for analysis, and you usually get the result within a few days. Some clinics offer point-of-care tests. All you need to do for this is give a small sample of saliva, or a spot of blood from a pin prick, and you get the result there and then. Both of these types of test detect whether or not you have HIV antibodies. The downside is that it generally takes a few weeks for your immune system to start producing HIV antibodies after you first got infected, and occasionally up to 6 months. This means, you can test HIV negative, but may in fact be HIV positive. There are other diagnostic tests that can detect the presence of HIV earlier, including the HIV p24 antigen test and the nucleic acid amplification test, but they are not used extensively at this time
What are the symptoms of HIV/AIDS?
If you are infected with HIV and have not taken any HIV treatment, you can expect three stages of illness as the infection progresses:
Timeline of the progression of an HIV infection
- Acute infection occurs shortly after HIV first enters your body. HIV infects your CD4 cells and rapidly multiplies. Within a week or two, the infection takes hold and signs and symptoms of fever, headache, fatigue, and swollen lymph glands make many people feel like they are getting the flu. At this time, your immune system is operating at full throttle, aggressively fighting the infection, and typically, after a few weeks, the flu-like symptoms will pass and you will start producing HIV antibodies.
- Clinical latency as its name suggests, is generally a time without symptoms. During this stage, your immune system and HIV have come into balance and the infection is partially controlled. However, HIV continues to slowly multiply and as time passes it steadily kills off your CD4 cells making you increasingly immunodeficient. A key point here is that during this time most people with HIV don’t look or feel sick, and may not even know that they are infected.
- AIDS starts when your immune system has become so weak it can no longer protect you from infection by other organisms and diseases. You may experience any or all of the following symptoms: rapid weight loss, night sweats, extreme fatigue, swollen lymph glands, chronic diarrhea, sores in your mouth, anus or genitals, pneumonia, brown or purplish lesions on your skin or in your mouth, memory loss and depression.
The US Centers for Disease Control and Prevention (CDC) have published a list of over 20 AIDS-defining diseases that may occur in the later stages of HIV infection, and that are used worldwide to diagnose AIDS for surveillance purposes. According to the CDC definition, if you are infected with HIV, you are considered to have AIDS if your doctor has diagnosed you with any one of the listed AIDS-defining diseases. Alternatively, your doctor can diagnose you with AIDS based on your CD4 cell count - it doesn’t apply to young children or babies, but if you are 6 years or older, you have AIDS if your CD4 cell count is less than 200 cells per microlitre, or if your CD4 cells are less than 14% of you total lymphocytes. Your susceptibility to AIDS-defining diseases is generally related to your CD4 cell count, which typically start when your CD4 cell count has dropped to around 500 cells per microlitre of blood.
Some of the most common AIDS-defining diseases that may cause AIDS symptoms are shown in the table below.
|CD4 cells per microliter of blood||AIDS-defining diseases|
|Around 500||Fungal infections (Candida): The first opportunistic infections that you are likely to get if you have HIV are minor fungal infections caused by an overgrowth of Candida, the fungus that causes diaper rash in babies. Candida infections commonly occur in the mouth and throat (oral candidiasis or thrush), airways and lungs, or vagina (vaginal candidiasis). This fungus typically forms white patches on your gums, tongue and lining of your mouth, and can make it so painful to swallow that you lose your appetite. An infection in your vagina will cause itching or burning, and soreness and redness accompanied by a thick white discharge.|
|500 to 200||Kaposi’s sarcoma: Kaposi’s sarcoma is a tumour caused by a human herpes virus. The tumour usually appears as purplish lesions on the skin of your legs or face, or inside your mouth, and can spread to other parts of your body without you knowing it. If the cancer spreads to your guts or lungs, it can cause bleeding or difficulty with breathing that can be life threatening.|
|200 to 100||Pneumocystis jiroveci pneumonia: Pneumocystis jiroveci pneumonia is a type of pneumonia that severely affects the lungs and is the most common opportunistic infection in people with AIDS. Signs and symptoms of pneumocystis can include shortness of breath, fever, dry cough and chest pain. It usually takes weeks or months to develop, but can be life threatening if not treated.|
|100 to 50||Cytomegalovirus: Cytomegalovirus is everywhere and it is thought that most people throughout the world have been exposed to it, but mostly didn’t notice. Nevertheless; like HIV, once you have the virus you have it for life. If you are HIV infected and have low CD4 cell counts, you should not be surprised if you get a cytomegalovirus infection in your gut, or your eyes (cytomegalovirus retinitis), where it may lead to blindness if you don’t get treatment.|
|less than 50||Mycobacterium avium complex: Mycobacterium avium complex exists everywhere in the environment and can infect the lungs and intestines of people with severe immunodeficiency. It can be deadly if it spreads to other parts of your body.|
How do you get HIV?
The most common way to get HIV is by having sex with an HIV infected person.
- HIV spreads from one person to another when certain body fluids (blood, semen, vaginal secretions, rectal fluids, and breast milk) from an HIV infected person come into contact with a mucous membrane in the nose, mouth, rectum, vagina, or penis of an uninfected person. Vaginal, anal, and oral sex all set the scene for HIV to spread from one person to another.
The 2nd most common way to get HIV is by injecting HIV directly into your body.
- This most commonly happens when HIV contaminated needles or syringes, or other drug injecting equipment is shared by injection drug users.
Image of a needle
It is worth knowing that HIV is not highly contagious, meaning it does not spread from one person to another very easily. It is not spread through the air, and because it does not live for long outside the human body you cannot get it simply by being around an HIV infected person. It is not spread through touching, hugging, sneezing or coughing, or by eating or drinking from common utensils. It is not spread by water, saliva, tears or sweat, or by using a drinking fountain or sitting on a toilet seat, and it is not spread by insects including mosquitoes or ticks.
How likely are you to get HIV?
Around 35 million people are currently living with HIV worldwide. About half of these are women and over 3 million are children. Every day 6,000 people become infected with HIV, which means over 2 million people are newly infected every year.
World map showing the prevalence of HIV/AIDS
Your chances of getting HIV depend on many factors. Although not always the case, it can happen the very first time you have sex with someone who is infected, or the first time you inject drugs with a contaminated needle. There are situations that increase the chances that it will happen to you, including:
- If your HIV infected sexual partner has another sexually transmitted disease such as herpes, hepatitis or tuberculosis.
- If your HIV infected sexual partner has particularly large numbers of HIV circulating in their bloodstream (a high viral load).
- If you frequently have unprotected sex with a partner you know is infected.
- If you frequently have unprotected anal or vaginal sex with multiple partners when you are unsure as to whether or not they have HIV infection.
How to avoid getting infected with HIV
To avoid getting HIV, you must prevent any contaminated body fluids from entering your body through your nose or mouth, vagina, anus, penis, or breaks in your skin. This can be done by practicing safe sex and safe drug use, which means:
- always use a condom
- get tested regularly - this is a must if you are having sex with someone you know has HIV, or if you are worried you might have been exposed to HIV, and
- never share intravenous needles, syringes, cookers, cotton, cocaine spoons, or eye droppers if you use drugs.
There are other ways you can catch HIV, although it very rarely happens. It is possible to become infected through a needle stick injury or blood transfusion, or by getting bitten by an HIV infected person. HIV can also be passed on from an infected mother to a baby during pregnancy, labour and birth, or via breast milk, but with proper medical treatment during pregnancy this is also rare.
How do you treat HIV/AIDS?
Antiretroviral therapy (ART) is the medicine used to treat HIV infection. It is a combination of three different medicines that is often taken as a single tablet and must be taken everyday to be of maximum benefit. ART is recommended for everyone infected with HIV. Although it is not a cure, if you have HIV it lets you live a longer, healthier life, and reduces the chances you will spread the virus to someone else.
HIV medicines work by preventing HIV from multiplying, which lowers the amount of virus in your bloodstream (viral load). Although the medicine does not get rid of HIV entirely, it gives your CD4 cells a chance to recover so that they can fight off opportunistic infections and cancers. If you don’t take ART, you are likely to die within 12 years from the time you first got infected. On the other hand, if you do take ART, you can have a life expectancy equal to or even higher than the general population.
If you test positive for HIV infection, your doctor will take a medical history, conduct a physical exam and order some more tests to find out how HIV is affecting your immune system. There are more than 20 HIV medicines available and several different ART combinations that may be suitable, depending on your individual needs. Three important tests that help your doctor decide which medicines will work best for you are:
- CD4 tests that measure your CD4 cell count.
- Viral load tests that measure the number of viruses in your bloodstream, and
- Drug resistance tests that find out whether or not the HIV you are infected with is resistant to any of the anti-HIV medicines that are available.
As HIV medicines are known to interact badly with some other medicines, the choice of therapy will also depend on what else you are taking. Later, your HIV medicine may need to be changed if you are having unpleasant side effects, or if your HIV becomes resistant to the medicine.
Consider the following:
- You might be one of the millions of people who use a lubricant during sex. If you are using latex condoms, you can have safer sex if you use a water-based lubricant rather than an oil-based lubricant. Why would that be? Oil-based lubricants like Vaseline, can weaken latex, making it more likely to break. So, only choose an oil-based lubricant if you are using polyurethane condoms.
- You might think that forgetting to take your HIV medicine now and then is not a big deal, but it is! Why would that be? HIV can multiply very quickly and sometimes it mutates, meaning it evolves into a new form. Forgetting to take your HIV medicine increases the chances that your HIV will multiply and mutate into a drug resistant form. If this happens, your HIV medicine will no longer work very well and HIV will do more damage to your immune system.
Want to join the conversation?
- why is AIDS called a syndrome and not a disease?(7 votes)
- AIDS is designated as a syndrome since a group of health problems (e.g. AIDS (+) patients are immunocompromised so they can acquire tuberculosis and hepatitis b...etc. at the same time) are characteristic of the disease(13 votes)
- Although there is no cure for HIV/AIDS yet, how was the discovery made that a 3rd chromosome genetic variation (mutation) called CCR5 Delta-32 discovered that can prevent a person contracting HIV, and how does it actually work and confer immunity?(1 vote)
- Well, HIV needs not only CD4 receptors to enter a cell, it also needs coreceptors. There are a lot of coreceptors, but the most common ones are CCR5 and CXCR4. In that case, there is a mutation in the CCR5 gene, which produces the CCR5 Delta-32 protein. So, the HIV can't bind to the CD4 cell, because it needs the CD4 and the CCR5 or the CXCR4. So, if a cell only express CD4 and CCR5 Delta-32, the HIV can't bind, thus the infection does not occur, but if the CXCR4 is expressed, or also expressed, the infecction can occur. So, these isn't an "immunity" against HIV, only a form of resistance. Even people with the mutation still can contract and have AIDS.(5 votes)
- If we're so advanced in technology how come we have not created a cure for HIV? We have an Ebola Cure and a vaccine. How come we don't have that for HIV?(2 votes)
- The HIV virus easily mutates. That makes it hard to come up with a cure, because by the time we might have one, the virus mutates to the point that it is ineffective.(3 votes)
- What about the window, incubation, and full blown stages?
I learnt that when i was in middle school though I was raised in Africa. Does it mean there's different ways AIDS affect people in different parts of the world?(1 vote)
- HIV does not affect people differently in different parts of the world, in general. My caution in that answer is that in the US, over 99% of HIV is HIV 1 and there is little HIV 2. HIV 2 is more likely in West Africa and it does have some different characteristics. But I think this is a detail that does not directly matter in terms of your question. It is more important to understand that the instructor was trying to give an overview and introduce ideas about the immune system. He just used different terms then you are used to and it is likely that you already know more about this disease than the average student. The window, is that time when diagnosis is not reliable because the person may not have circulating viral particles or antibodies and so the diagnosis is missed. This window varies with the individual and maybe up to 6 months early in the infection, which the instructor did state. During that time, one has more likelihood of a false negative test. Quick ELISA Tests in the U.S. are testing for HIV 1 and may test for both viral particles and antibodies, depending on the test, which improves their reliability. After unprotected sex, a doctor may advise a patient to have a test after 2 weeks, 3 months and 6 months to be sure that a patient with a negative test remains negative for HIV. However, as soon as a test is positive, it is typically considered reliable. Check out the CDC pages for reliable information on your questions, https://www.cdc.gov/hiv/default.html
The window period is the time between when a person gets HIV and when a test can accurately detect it. The window period varies from person to person, and is also different depending upon the type of HIV test. Most HIV tests are antibody tests. It takes time for the body to produce enough antibodies for an HIV test to show that a person has HIV.”(3 votes)
- though macrophages are enlarged monocytes still they belong to lymphoid linegae or lymphoid group why is it so(2 votes)
- Macrophages and monocytes have big roles in the INNATE immune system. They belong to a group of immune cells (specialized in finding and eating bacteria, viruses, etc) called Phagocytes: dendritic cells, MACROPHAGES, and granulocytes. Macrophages start out as white blood cells called monocytes. Monocytes then migrate to the tissue where they turn into macrophages. Once mature, macrophages play a very important role in the immune system. They "eat" up pathogens by a process: phagocytosis. Once inside the cell, the pathogens are broken up, and parts of them are displayed on the surface of the cell. This is to signal to the other immune cells, and alert them to an invading pathogen. Macrophages therefore play a key part in alerting the rest of the immune system of invaders. They are kind of like messengers.(5 votes)
- If you contract a disease like Pneumonia or any STD during the Clinical Latency period, will they take a long time to be cured? Can the doctors use this as a sign to diagnose HIV Virus if not known otherwise?(2 votes)
- What are the three things that happen as the end product of all of the cellular events that happen due to HIV infection?(1 vote)
- "A virus is a small infectious organism (...)", so a virus is, alive?(1 vote)
Most would say they are not alive.(2 votes)
- what is the biggest difference between HIV and Aids do you think(1 vote)
- Is HIV only latent during the second phase or is it latent before the 1st phase and also during the second phase? And does Reverse Transcriptase happen as soon HIV enters and destroys CD4 cells?(1 vote)
- To answer your second question: Yes. The process of reverse transcription happens as soon as an HI-virus infects a CD4 cell. The destruction of CD4 cells due to HIV can only happen if CD4 cells are infected by HIV. (There is a hypothetical scenario where CD4 cells can be destroyed due to HIV before CD4 cells of your own body are infected but that is a complicated and unrealistic case.)
Your first question depends on the definition of "latent": If you consider latent as a state of infection without symptoms, then yes.
However, it is natural for almost all diseases to have a phase at the beginning where there are no symptoms due to the low abundance of the pathogen at the time of infection. This period of time is usually referred to as the incubation period.(1 vote)