HIV infection is a disease caused by the human immunodeficiency virus (HIV). The condition gradually destroys the immune system, which makes it harder for the body to fight infections. Most people infected with HIV eventually develop AIDS. These individuals mostly die from opportunistic infections or malignancies associated with the progressive failure of the immune system. HIV progresses to AIDS at a variable rate affected by viral, host, and environmental factors; HIV-specific treatment delays this process. Most will progress to AIDS within 10 years of HIV infection: some will have progressed much sooner, and some will take much longer. Treatment with anti-retrovirals increases the life expectancy of people infected with HIV. Even after HIV has progressed to diagnosable AIDS, the average survival time with antiretroviral therapy was estimated to be more than 5 years as of 2005. Without antiretroviral therapy, someone who has AIDS typically dies within a year.
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors. HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid, and breast milk. When HIV infection becomes advanced it often is referred to as AIDS. It generally occurs when the CD4 count is below 200/mL and is characterized by the appearance of opportunistic infections. These are infections that take advantage of a weakened immune system and include:
• Pneumocystis carinii pneumonia
• Extreme weight loss and wasting; exacerbated by diarrhea which can be experienced in up to 90% of HIV patients worldwide
• Meningitis and other brain infections
• Fungal infections
• Malignancies such as lymphoma, cervical cancer, and
• Kaposi’s Sarcoma
Today we know that Acquired Immune Deficiency Syndrome (AIDS) is a disease and not a syndrome. A syndrome is commonly used to refer to collections of symptoms that do not have an easily identifiable cause. This name was more appropriate 13 years ago, when doctors were only aware of the late stages of the disease and did not fully understand its mechanisms. A more current name for the condition, regardless of an AIDS diagnosis, is HIV Disease. This name is more accurate because it refers to the pathogen that causes AIDS and encompasses all the condition’s stages, from infection to the deterioration of the immune system and the onset of opportunistic diseases.
However, AIDS is still the name that most people use to refer to the immune deficiency caused by HIV. • Acquired — because it is a condition that has to be contracted. It cannot be inherited or transmitted through the genes. • Immune — because it affects the body’s immune system, the part of the body that fights off diseases. • Deficiency — because it makes the immune system stop working properly. • Syndrome — because people with AIDS experience a number of different symptoms and opportunistic diseases.
Four stages of HIV infection:
1. Incubation Period
In the majority of the infected population, HIV remains asymptomatic for years. The only way to know if you have HIV is to be tested. It is important to know, however, that it may take up to six months after exposure to the HIV virus before you will test positive on an HIV antibody test, although most infected people will test positive within 3 months. A negative test, therefore, isn’t a reliable indicator of your infection status if you were only exposed last week. Tests that look directly for HIV RNA, the virus’ genetic material, can detect an infection earlier, but are harder to find. 2. Acute HIV infection
The initial infection with HIV generally occurs after transfer of body fluids from an infected person to an uninfected one. The first stage of infection, the primary, or acute infection, is a period of rapid viral replication that immediately follows the individual’s exposure to HIV leading to an abundance of virus in the peripheral blood with levels of HIV commonly approaching several million viruses per mL. This response is accompanied by a marked drop in the numbers of circulating CD4+ T cells. This acute viremia is associated in virtually all patients with the activation of CD8+ T cells, which kill HIV-infected cells, and subsequently with antibody production, or seroconversion. The CD8+ T cell response is thought to be important in controlling virus levels, which peak and then decline, as the CD4+ T cell counts rebound to around 800 cells per µL (the normal blood value is 1200 cells per µL ). A good CD8+ T cell response has been linked to slower disease progression and a better prognosis, though it does not eliminate the virus.
During this period (usually 2–4 weeks post-exposure) most individuals (80 to 90%) develop an influenza or mononucleosis-like illness called acute HIV infection. Because of the nonspecific nature of these symptoms, they are often not recognized as signs of HIV infection. Even if patients go to their doctors or a hospital, they will often be misdiagnosed as having one of the more common infectious diseases with the same symptoms. Consequently, these primary symptoms are not used to diagnose HIV infection as they do not develop in all cases and because many are caused by other more common diseases. However, recognizing the syndrome can be important because the patient is much more infectious during this period.
3. Latency stage
A strong immune defense reduces the number of viral particles in the blood stream, marking the start of the infection’s clinical latency stage. Clinical latency can vary between two weeks and 20 years. During this early phase of infection, HIV is active within lymphoid organs, where large amounts of virus become trapped in the follicular dendritic cells (FDC) network. The surrounding tissues that are rich in CD4+ T cells may also become infected, and viral particles accumulate both in infected cells and as free virus. Individuals who are in this phase are still infectious. During this time, CD4+ CD45RO+ T cells carry most of the proviral load.
When CD4+ T cell numbers decline below a critical level of 200 cells per µL, cell-mediated immunity is lost, and infections with a variety of opportunistic microbes appear. The first symptoms often include moderate and unexplained weight loss, recurring respiratory tract infections (such as sinusitis, bronchitis, otitis media, pharyngitis),prostatitis, skin rashes, and oral ulcerations. Common opportunistic infections and tumors, most of which are normally controlled by robust CD4+ T cell-mediated immunity then start to affect the patient.
Typically, resistance is lost early on to oral Candida species and to Mycobacterium tuberculosis, which leads to an increased susceptibility to oral candidiasis(thrush) and tuberculosis. Later, reactivation of latent herpes viruses may cause worsening recurrences of herpes simplex eruptions, shingles, Epstein-Barr virus-induced B-cell lymphomas, or Kaposi’s sarcoma. Pneumonia caused by the fungus Pneumocystis jirovecii is common and often fatal. In the final stages of AIDS, infection with cytomegalovirus (another herpes virus) or Mycobacterium avium complex is more prominent. Not all patients with AIDS get all these infections or tumors, and there are other tumors and infections that are less prominent but still significant.
As a national and global epidemic, the degree of morbidity and mortality caused by caused by HIV or AIDS. At the end of 2002, it was estimated that there were 42 million people living with HIV / AIDS and that more than 25 million had died of the infection. During the same year, 5 million were newly infected with the virus, and for the first time, women and young people 15 to 24 years of age accounted for 50% of HIV infections. In the year 2007, it was estimated that 33.2 million people lived with the disease worldwide, and that AIDS had killed an estimated 2.1 million people, including 330,000 children.
In the Philippines, cases were estimated to be 29 each month in the year 2007 and continue on until 2008. As of September 2008, the Department of Health (DOH) AIDS Registry in the Philippines reported 3,456 people living with HIV/AIDS. The Philippines is a low-HIV-prevalence country, with less than 0.1 percent of the adult population estimated to be HIV-positive.
AIDS is caused by the human immunodeficiency virus or HIV. Human immunodeficiency virus (HIV) is a lentivirus (a member of the retrovirus family) that causes acquired immunodeficiency syndrome (AIDS), a condition in humans in which the immune system begins to fail, leading to life-threatening opportunistic infections. Infection with HIV occurs by the transfer of blood, semen, vaginal fluid, pre-ejaculate, or breast milk. Within these bodily fluids, HIV is present as both free virus particles and virus within infected immune cells. The four major routes of transmission are unsafe sex, contaminated needles, breast milk, and transmission from an infected mother to her baby at birth (Vertical transmission).
Screening of blood products for HIV has largely eliminated transmission through blood transfusions or infected blood products in the developed world. HIV primarily infects vital cells in the human immune system such as helper T cells (specifically CD4+ T cells), macrophages, and dendritic cells. HIV infection leads to low levels of CD4+ T cells through three main mechanisms: firstly, direct viral killing of infected cells; secondly, increased rates of apoptosis in infected cells; and thirdly, killing of infected CD4+ T cells by CD8 cytotoxic lymphocytes that recognize infected cells. When CD4+ T cell numbers decline below a critical level, cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections.
HIV is present to variable degrees in the blood and genital secretions of virtually all individuals infected with HIV, regardless of whether or not they have symptoms. The spread of HIV can occur when these secretions come in contact with tissues such as those lining the vagina, anal area, mouth, or eyes (the mucus membranes), or with a break in the skin, such as from a cut or puncture by a needle. The most common ways in which HIV is spreading throughout the world include sexual contact, sharing needles, and by transmission from infected mothers to their newborns during pregnancy, labor (the delivery process), or breastfeeding. (See the section below on treatment during pregnancy for a discussion on reducing the risk of transmission to the newborn.)
There is little evidence that HIV can be transferred by casual exposure, as might occur in a household setting. For example, unless there are open sores or blood in the mouth, kissing is generally considered not to be a risk factor for transmitting HIV. This is because saliva, in contrast to genital secretions, has been shown to contain very little HIV. Still, theoretical risks are associated with the sharing of toothbrushes and shaving razors because they can cause bleeding, and blood can contain large amounts of HIV. Consequently, these items should not be shared with infected people. Similarly, without sexual exposure or direct contact with blood, there is little if any risk of HIV contagion in the workplace or classroom.
Signs and Symptoms
• Acute HIV infection
Main symptoms of acute HIV infection.
• Symptomatic HIV infection or Acquired Immunodeficiency Syndrome – Moderate and unexplained weight loss
– Recurring respiratory tract infections (such as sinusitis, otitis media, bronchitis, pharyngitis)
– Prostatitis, skin rashes, and oral ulcerations
– Oral candidiasis and Tuberculosis caused by Candida species and Mycobacterium tuberculosis respectively.
– Reactivation of latent herpes viruses may cause worsening recurrences of herpes simplex eruptions, shingles, Epstein-Barr virus-induced B-cell lymphomas, or Kaposi’s sarcoma.
– Pneumonia caused by the fungus Pneumocystis jirovecii is common and often fatal. – In the final stages of AIDS, infection with cytomegalovirus (another herpes virus) or Mycobacterium avium complex is more prominent.
WHO Case Definition for AIDS Surveillance
For the purpose of AIDS surveillance an adult or adolescent (>12 years of age) is considered to have AIDS if at least 2 of the following major signs are present in combination with at least 1 of the minor signs listed below, and if these signs are not known to be due to a condition unrelated to HIV infection.
– Weight loss >10% of body weight
– Chronic diarrhea for more than 1 month
– Prolonged fever for more than 1 month (intermittent of constant)
– Persistent cough for more than 1 month
– Generalized pruritic dermatitis
– History of herpes zoster
– Chronic progressive or disseminated herpes simplex infection – Generalized lymphadenopathy
The presence of either generalized Kaposi sarcoma or cryptococcal meningitis is sufficient for the diagnosis of AIDS for surveillance purposes.
Expanded WHO Case Definition for AIDS Surveillance
For the purpose of AIDS surveillance an adult or adolescent (>12 years of age) is considered to have AIDS if test for HIV antibody gives a positive result, and 1 more of the following conditions are present: – >10% body weight loss or cachexia, with diarrhea or fever, or both, intermittent or constant, for at least 1 month, not known to be due to a condition unrelated to HIV infection – Cryptococcal meningitis
– Pulmonary or extra-pulmonary tuberculosis
– Kaposi sarcoma
– Neurological impairment that is sufficient to prevent independent daily activities, not known to be due to a condition unrelated to HIV infection (i.e. trauma or cerebrovascular accident) – Candidiasis of the esophagus (which may be presumptively diagnosed based on the presence of oral candidiasis accompanied by dysphagia)
– Clinically diagnosed life-threatening or recurrent episodes of pneumonia, with or without etiological confirmation – Invasive cervical cancer
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