HIV (human immunodeficiency virus) is a growing problem in the world. In 2014, an estimated 25,000 people in the Netherlands lived with the condition, a number that increases by about a thousand every year. An important role in this is that there is a number of years between the first infection with HIV and the complaints it causes, called AIDS (Aquired ImmunoDeficiency Syndrome). However, during this intermediate, symptom-free period it is possible to infect other people. Forms of diagnostics include the ELISA, PCR and HIV rapid test. This article discusses the symptoms and diagnostics that indicate the presence of HIV.
Table of contents
- Pathogenesis
- Infection
- Symptoms
- Diagnostics
- Types of tests
Pathogenesis
For a good understanding of the method of infection, the development of the complaints and research into the possible presence of HIV, it is important to know how the virus works. HIV is an abbreviation for human immunodeficiency virus. It is a lentivirus of the retrovirus subtype that mutates rapidly. It mainly infects CD4+ T cells in humans, these are cells that play an important role in the immune system. The virus contains RNA, a kind of code that is necessary for human cells to reproduce. The virus cannot spread without a host. This RNA is enclosed by a membrane, on which there are proteins that play a role in entering the human cell.
The human immune cells process the RNA presented by the virus into their DNA, resulting in production of the virus in the human immune cell. This continues until it is unsustainable for the cell, after which a large number of viruses are released. These are ready to infect the next cell. The virus responds to the activity of the immune cell. In an active immune cell it will be produced the most. In a quiet immune cell it will be copied less often.
The processing of RNA into DNA is very sensitive to errors. This is one of the reasons why it is difficult for the immune system to recognize it, and a minimally changed variant often arises. As a result, previously formed antibodies can suddenly no longer recognize the virus. There are two types of HIV, namely HIV1 and HIV2. HIV1 is the most common and most contagious form. HIV2 is mainly limited to West Africa.
In summary, an infection with HIV creates recognition points (antigens) to which the body can respond by means of antibodies. There is also RNA present in the blood, which contains a code for new replicas. The number of immune cells slowly decreases over time.
Infection
HIV spreads due to the presence of the virus in body fluids such as blood, semen, vaginal fluid and pre-cum. With a sufficient viral load (the concentration of viruses), infection can occur. This allows the virus to spread through unprotected vaginal or anal contact. During pregnancy, infection is possible from mother to child, including during breastfeeding. Other sources of infection include a needlestick injury with a needle contaminated with HIV-positive blood and a blood transfusion with contaminated donor blood.
CD4 cell count (Blue) and HIV concentration (Red) during the course of the infection / Source: Jurema Oliveira, Wikimedia Commons (CC BY-SA-3.0)
Symptoms
The complaints that arise after infection with HIV can be divided into two different groups. The acute complaints arise a few weeks after the infection. These complaints are little different from flu (also an infection with a virus), a reaction in which the body attacks the virus present. Symptoms of this include fever, fatigue, headache, swollen lymph nodes and these usually last 1 to 2 weeks. During this period the virus is present in high concentrations, making it very contagious at that time. After this it takes several years (usually 2 to 10 years, the so-called latent phase) before it results in AIDS, the syndrome that describes the reduced immune system. HIV and the immune cells are then relatively in balance.
AIDS describes the syndrome that arises as a result of reduced immunity due to infection with HIV. The reduced immune system in itself does not cause any complaints, these arise because people are increasingly susceptible to opportunistic infections. These are infections that normally cause short-term complaints or to a much lesser extent, but can be seized much more easily due to the reduced immune system. These complaints can differ per patient and per person. For example, a child in Africa will be exposed to very different opportunistic infections than a middle-aged person in Europe.
The primary infection is followed by a prolonged asymptomatic phase. In the symptomatic phase, the following complaints are most characteristic:
Oral candidiasis infection / Source: Sol Silverman, Jr., DDS, Wikimedia Commons (Public domain)
Candidiasis (‘Thrush’)
Is a fungal infection of the mouth, throat and skin, nails or vagina. This is caused by the fungus called Candida Albicans. The complaints mainly consist of painful red or white spots.Cryptococcus: An infection with Cryptococcus neoformans can lead to, among other things, meningitis (with complaints of headache and fever) or pneumonia (with fever, coughing and shortness of breath).
CMV (Cytamegalovirus)
If CMV flares up, it can result in, among other things, a gastrointestinal infection, pneumonia and meningitis.
TB (Tuberculosis)
This is the most common cause of death in people with AIDS worldwide, especially in developing countries. This mainly causes complaints indicating pneumonia, but other organs are also frequently affected.
Other, more general complaints
Weight loss, night sweats, unexplained fatigue, swelling of lymph nodes, diarrhea lasting more than a week, impaired memory, difficulty concentrating and polyneuropathy. Most of these complaints arise from contamination with opportunistic infections. In addition, due to reduced immunity, people with HIV infection have an increased risk of developing cancer. A well-known example is Kaposi’s sarcoma.
Diagnostics
The diagnosis of the presence of HIV can be divided into two groups, consisting of people with a suspicion of a possible primary infection and a second group with a suspicion of developing AIDS.
Sensitivity and specificity
Sensitivity is a term used for the number of positive test results among the group of HIV positive people. Specificity describes the number of negative test results among the group without HIV. In an ideal test both would be 100%. The different tests available for diagnosis have different sensitivity and specificity. A test with high sensitivity (for example >99%) results in missing very few infections. This is desirable when screening donor blood. This is also a desirable characteristic when diagnosing a large group of people as a first screening.
Window
There is a period of time (often described with the term ‘window’) between infection and the presence of factors measurable in the blood that can confirm HIV infection. As a result, an HIV test immediately after infection is absolutely not reliable to rule out the condition as a result of, for example, a needlestick injury. This is because the body needs time to produce, for example, the antibodies to be measured. Another cause is that the virus itself is present in too low a concentration to measure.
Administration of HIV finger prick test / Source: LGBT Free Media Collective, Wikimedia Commons (CC BY-SA-3.0)
Types of tests
Rapid test
There is a rapid test that provides the result within 30 minutes. The most sensitive are the serum (blood) tests with a sensitivity of 96.4-100%. Another relatively reliable test is a finger prick test, which has a sensitivity of 94.5-99%. Tests that rely on results in urine and saliva have significantly lower sensitivity (<90%). With some tests you have to wait three months after the last exposure before the test can make a good statement. Negative is always negative, but a positive result must be further confirmed. You can order a home test; if the result is positive, it is wise to contact a doctor.
A rapid test can also be of added value in determining whether there is an indication for PEP (post exposure prophylaxis). This may involve contamination in the event of a needlestick injury from an HIV positive source.
ELISA
ELISA (Enzyme linked immunosorbent assay) is a test in which the blood is diluted approximately 400 times. After this, the blood is exposed to a plate with HIV antigens. If antibodies stick to these antigens, the diagnosis is confirmed. This measures the antibodies in the body. ELISA has a high sensitivity and specificity of almost 100%, making it ideally suited for diagnostics.
PCR
PCR stands for polymerase chain reaction. In this test, parts of the HIV RNA are multiplied. This test is almost as reliable as the ELISA. False negative results can be caused by a high diversity of HIV. This also misses HIV type 2. The test is so obsolete compared to ELISA that it is virtually no longer used.
Markers for progression
After confirming the diagnosis, it is important to monitor progression. This can be done in particular by measuring the number of immune cells, the so-called CD4+ count. The viral load of patients is also determined over time.
