AIDS: What is it?
Acquired immunodeficiency syndrome ( Acquired Immunodeficiency Syndrome: AIDS) is a viral immune disease, which mainly affects young adults and children.
The actual definitive name of the virus is HIV (Human Immunodeficiency Virus) of which two types are known (1 and 2). The immune disorder typical of the disease is largely due to the selective deficiency of a subpopulation of cells indispensable to the immune response, called CD4 + T lymphocytes, which are infected by the virus. Acquired immunodeficiency syndrome and tumors and related syndromes are the direct or indirect consequence of an HIV-1 and HIV-2 infection.
Index Further information
Diffusion and contagionThe HIV virusSymptoms of AIDS and prognosisDiagnosis AIDS and opportunistic infectionsAIDS and tumorsCare and therapy AIDS preventionEpidemiology
The epidemic is most likely originated in equatorial Africa, an area in which the virus had been present at least since the 1950s. From here it spread at the end of the 1970s in the Caribbean islands and in some metropolitan areas of the USA and Northern Europe through infected subjects.
The intense commercial and tourist exchanges between areas initially affected by the epidemic and areas not yet affected, and the use of infected blood for transfusion purposes from epidemic areas (in particular the USA) have contributed to the spread of HIV infection in all the world in the early eighties.
The epidemiological role of HIV-2, which still today has a limited diffusion in some West African states and the frequency with which cases of disease develop starting with HIV-2 infection is of little relevance for the time being significantly lower than that observed in HIV-1-positive subjects.
The World Health Organization estimates that HIV-1 has already infected about 40 million people worldwide.
In recent years there has been an increase in cases attributable to sexual transmission.
Contagion
Transmission by parenteral route
HIV can be transmitted by transfusions of blood or blood products (blood derivatives without red blood cells such as plasma or platelets) infected, with the inoculation of small quantities of contaminated blood through the exchange of syringes between drug addicts or accidental puncture with infected needles or instruments stained with blood (razors, blades, tweezers, scissors). All these modalities are part of the so-called parenteral transmission .
Transmission by Sex
The transmission can also take place with sexual relations, both homosexual and heterosexual, and is defined as a sexual transmission . The virus contained in the seminal fluid (sperm) of seropositive males can infect cells susceptible to the vaginal or rectal mucosa or directly reach the usual target cells, that is the T lymphocytes, through lesions of the mucous surfaces, immediately below which are the same lymphocyte cells.
The risk increases if during the sexual intercourse small traumas of the mucous membranes are provoked, that determine the escape of blood. Infection can also be transmitted by women, with infected cervical and vaginal secretions . Another risk factor for sexual transmission is the presence of sexually transmitted infections such as syphilis, gonorrhea and genital herpes.
Vertical Transmission
An HIV-positive woman can transmit the infection to her child during pregnancy (by the blood that normally passes from the mother to the fetus), and is called maternal-fetal transmission, at the moment of delivery (by vaginal secretions and blood) or after birth with breastfeeding (the virus is also contained in breast milk). These last two modes are called vertical transmission .
How high is the risk of infection?
The risk of infection is very different and varies from case to case in relation to the mode of exposure and the host's predisposing factors.
The risk of transmitting the infection through a transfusion is very high (over 90%), while for heterosexual and homosexual relationships it is assessed with a risk ranging from 0.1 to 3% for a receptive anal relationship, to a 0, 03-0.2% for a vaginal receptive ratio to a 0.03-1% for a vaginal insertive relationship. In the two main populations with risk behaviors (homosexuals and drug addicts) the infection rates range from 5 to 70%. The probability of maternal-fetal transmission ranges from rather high percentages in Africa (35%) to lower percentages in Europe (14%).
The likelihood of becoming infected with occasional exposures to infected materials by staff assigned to assisting HIV positive patients or handling contaminated biological samples (less than 1/1000) is very low. Although the virus is present in saliva and in tears, no transmission of infection has been reported for the moment in subjects exposed only to these biological fluids. Other transmission routes have not yet been documented: therefore, they do not expose social contacts in the family, work or school environment to the risk of infection; frequenting public places (including bars, restaurants and swimming pools); the use of means of transport; the common use of tableware and furnishings; food and water. Transmission of the virus by air (droplets of spit, spit, coughing) through the usual manifestations of courtesy and affection (handshakes, hugs, kisses), with biological fluids (urine, saliva, tears) has not been demonstrated., sweat) or by means of vectors (mosquitoes, other insects and animals).
The dynamics of the spread of the virus seems to take on different characteristics depending on the geographic areas affected by the epidemic: in the USA and in Europe the disease has a higher incidence in males aged between 20 and 50 years. It predominantly affects subjects with risky behavior (homo or bisexual and drug addicts), although transmission is increasingly common through heterosexual relationships.
Transmission with blood or blood products is a thing of the past and is currently exceptional, due to the introduction of strict screening tests on infected blood.
