Unfortunately, up to now, most estimates of the number of HIV-infected people have been overblown. As early as 1983, selected scientists, and consequently the media, trumpeted estimates of 1 to 3 million. At the time, these estimates were exaggerated. Now, however, the AIDS epidemic is 10 years old, and scientists have tabulated over 200,000 total registered AIDS cases, and also have HIV screening results from hundreds of hospitals, hundreds of testing centers, and millions of armed forces recruits. Consequently, the current I million estimate carries a lot of weight.
In order for a person to catch AIDS (HIV infection), the Human Immunodeficiency Virus (HIV) must travel from the inside of one person to the inside of another person, arriving with its RNA strand(s) intact. Then the virus, or its intact RNA strand(s) must get into the new host's bloodstream and then successfully find and enter a T-cell. Once inside a host cell, HIV can prepare for replication. After replication, replica viruses infects other host cells, probably attaching to new host cells when the infected host cell collides with other cells in the bloodstream.
Generally, more than one virus enters the body at one time. More likely, a person encounters dozens, hundreds, or thousands of viruses (or virus-infected cells) during exposure. The more viruses present, the better the chance of one or more viruses succeeding in finding a host cell and replicating.
Viruses are not able to enter the body through intact skin. Therefore viruses must enter the body through an open wound(s) or one of a number of possible body openings. Most of these body openings contain mucous membranes. Mucous membranes are thin tissues which protect many openings and passages in the human body. These membranes secrete mucus. Which contains anti-germ chemicals and keeps the surrounding tissues moist. There are mucous membranes in the mouth, inside the eyelids, in the nose and air passages leading to the lungs, in the stomach, along the digestive tract, in the vagina, in the anus, and inside the "eye" of the penis. Many viruses, if placed on the surface of a mucous membrane, can travel through the membrane and enter the tiny blood vessels inside.
The mucous membranes of the eyes and mouth are often doorways into our bodies for highly infectious viruses such as the flu. You can catch the flu from a person in the following manner: the person coughs in his or her hand, you shake hands soon afterward, and then your virus-carrying hand touches your eye or mouth.
The flu is highly infectious because the flu virus lives in the lungs, throat, and sinuses. Therefore, a high concentration of flu viruses is present in the sputum of an infected person. (Sputum is the substance expelled by coughing or by clearing the throat. Concentration is the number of viruses per unit of volume.) Coughing forces many viruses out of the lungs and into the air or onto the sick person' s hand or handkerchief. The flu virus easily crosses the mucous membrane.
The danger with AIDS is very different. With AIDS, the major infection sites are the bloodstream and the central nervous system. While HIV-carrying macrophages (roving white blood cells that engulf invaders, but are susceptible to HIV infection) are found in the connective tissues of the lung and in oral and mucous membranes, the number of viruses present does not seem great. Thus, HIV is present in low concentrations, if at all, in saliva and sputum. So coughing should not expel a large quantity of HIV, if any. Apparently, HIV cannot cross the mucous membrane very easily, and large concentrations of HIV are probably necessary.
In an infected person, HIV is found in any body fluid or substance which contains lymphocytes (T4-cell and company). Substances containing lymphocytes include: blood, semen, vaginal and cervical secretions, mother's milk, saliva, tears, urine, and feces.
The presence of HIV within a substance does not necessarily mean the substance is capable of transmitting HIV infection. All of these substances are capable, in theory, of transmitting disease; but in reality, the most dangerous substances seem to be blood, semen, and cervical and vaginal secretions, and perhaps feces. Despite a lot of looking, no one has been able to find a clear cut case of saliva causing transmission, although kissing theoretically could. See "Kissing."
The concentration of HIV in these substances is very important when it comes to infectivity. (Concentration is "number of viruses per unit of volume") If a substance contains a high concentration, that is, a lot of viruses, then it is more likely HIV can be transmitted by the substance. Below a certain concentration of viruses, the substance can not effectively transmit HIV infection.
The importance of concentration is illustrated by the situation with sperm and pregnancy. If a male's semen contains fewer than 20 million sperm cells per milliliter (cubic centimeter), than it is unlikely that the male will be able to impregnate a female. Similarly, if the concentration of a virus is too low in sputum or any other substance, then it is unlikely to transmit infection.
HIV is also in pre-ejaculate fluid. Pre-ejaculate fluid oozes from the tip of the penis after prolonged sexual excitation, but before ejaculation. Therefore, pre-ejaculate fluid should be considered potentially infectious.
The concentration of HIV in these substances seems to be not as high as the concentration of HIV in semen and blood, but, these substances are infectious and can transmit HIV infection.
In theory, saliva can transmit HIV infection but, so far, it doesn't seem to have happened in real life. Kissing is discussed in more detail in the next section.
If HIV is contained in any of the aforementioned substances (blood, semen, vaginal and cervical secretions, urine, feces, mother's milk, saliva, tears) and these substances leave the body, the HIVs in these substance are capable of remaining infectious until these substances dry up, depending on circumstances, probably a matter of minutes or hours. If any of these substances stay moist, viruses contained in them can survive much longer. For example, in "water' and blood solutions (10% blood, 90% saline), HIV can survive at room temperature for 2 weeks. In refrigerated blood, such as blood used for transfusions, HIV can survive indefinitely.
Instructions on how to handle these substances follow in the Chapter "Preventing AIDS."
Most known cases of HIV infection have been transmitted through sexual contact, transfusions of blood and blood products, sharing contaminated intravenous (IV) needles, and passage of the virus from mother to unborn child.
Being exposed to a virus does not mean that a person is going to catch the virus. Exposure does not necessarily mean transmission. For example, when a person with the flu sneezes in the face of another person, the sneeze recipient may or may not contract the flu. Any number of factors contribute to this situation.
Proven or suspected methods of HIV transmission are discussed here. Prevention methods are discussed in "Preventing AIDS."
Anal intercourse involves inserting one person's penis into the anus of another person. From the body's viewpoint, anal intercourse is not a great idea. The anus is biologically designed for the excretion of feces. Evidently, medical disorders can arise from frequent and/or rough anal intercourse.
During anal intercourse, the receptive partner is the partner at greatest risk of catching HIV. The receptive partner is the person whose anus is being penetrated. This high risk for receptive partner exists whether the receptive partner is male or female.
Previously, it was thought that anal intercourse transmitted HIV infection because, during anal intercourse, the penis opened bleeding wounds inside the receptive partner's anus. These bleeding wounds were thought to be the doorway by which HIV directly entered the bloodstream to reach and infect T4-cells.
Now, it appears that the presence of bleeding wounds in the anus is not necessary for HIV transmission to take place. Macrophages are present, roving over the surfaces of the anus. HIV may infect these macrophages directly. Also, HIV is probably able to cross the mucous membrane and enter the tiny blood vessels inside. No damage to the wall of the anus may be necessary for HIV transmission to take place. According to a statistical study, rectal douching after anal intercourse increases the risk of HIV infection.
"Fisting" is the insertion of the fingers, or the entire hand into the anus. It might be considered a form of anal intercourse. According to a statistical study, fisting carries a slight risk for the insertive partner. There is little risk for the receptive partner. The risk to the insertive partner probably comes from contact with feces or with blood from the anus. People's hands often have small, invisible wounds around the cuticles of the fingernails; these may provide doorways into the body for the virus. Or, there could be an anus-to-hand to mouth transmission of the virus. This increased risk for the insertive partner could be a statistical quirk. If the risk does exist, no one yet knows its true cause.
Apparently, HIV transmission from males to females occurs more effectively than from females to males. This greater risk seems to be true for most sexually transmitted diseases: the female is at greater risk. ("Receptive partner" can be substituted for "female" in case of homosexual sex) A male's exposure to the female (or receptive partner) is fleeting; but the male leaves potentially contaminated semen in the vagina. Usually the semen remains in the female long after intercourse is over. The longer a person is exposed to germs, the more likely he or she is to catch the disease.
Male to female: If the male is infected, he deposits HIV-infected semen inside the female's vagina. Again, previously it was thought that inside a female's vagina, small wounds and bleeding may occur during sex or for a number of reasons, providing a doorway for HIV into the bloodstream. Bleeding wounds inside the vagina are probably not necessary.
Certain conditions may make a woman's vagina more susceptible to infection. For example, cervicitis (inflammation of the cervix) is a common condition in females, which makes the surface of the cervix and the vagina more likely to bleed. Cervicitis may be caused by IUD contraceptives devices and by sexually transmitted diseases such as gonorrhea, syphilis, and Chlamydia infection.
Females probably do not have an increased risk for catching HIV during menstruation. Menstrual bleeding is actually the shedding of the tissues of the uterus (womb). Menstrual blood flows from the uterus, through the cervix, and into the vagina. There is no vaginal wound for entry by HIV.
Again, it should be noted, that the current consensus is that wounds may not be necessary, since HIV may directly infect macrophages, which rove the mucous membrane surfaces. Also, HIV may be able to directly cross the mucous membrane and enter the blood vessels therein.
The vaginal secretions contain anti-germ chemicals. The vagina, being designed to accept foreign objects, has substantial immune defenses. This may explain why vaginal intercourse apparently does not transmit HIV infection as effectively as anal intercourse.
Female to male: Males can catch HIV from infected females. The method of transmission is not clear. It may be possible for HIV infection to come from menstrual blood or from contact with a female's vaginal or cervical secretions.
The concentration of HIV in these substances does not seem very high (compared with blood and semen), still the concentration is sufficient for HIV transmission to take place. Small amounts of blood may also be present in the vagina due to rough sexual intercourse or to other vaginal conditions.
In males, the doorway for HIV into the body may be very small wounds on the head of the penis, the mucous membranes lining the urethra (the "eye" of the penis is the opening of the urethra), or the glands which intersect the urethra at the base of the penis.
The condition of the cells lining the urethra may be important in male susceptibility to infection. The health of the cells may be affected by STDs (sexually transmitted diseases) or other irritants.
Once inside the mouth, HIV may penetrate the mucous membranes of the mouth, or enter the bloodstream via a number of possible doorways, including any small wound such as cold sores, bleeding gums (inflicted by toothbrush or dental floss, or rough kissing), and self-inflicted bites. Macrophages, which are susceptible to HIV infection, are also present.
It is possible, with some germs, for infection to pass from one person's mouth to the other person's penis, vagina, or anus. With HIV, this event is possible in theory, but seems unlikely owing to HIV's low concentration in saliva.
Blood, a highly infectious substance, may be present in the either partner's mouth, the male's urethra, the female's vagina, in a male's or female's anus from sores or from rough sexual intercourse, and/or in the female's vagina during menstruation.
There are no proven cases of individual people catching HIV from oral sex, but several suspected cases have come into light. Several homosexual males claim to have had only penis-to-mouth oral sex, including ejaculation, with their HIV-infected partner and to have become infected themselves. These cases are not confirmed. Several statistical studies suggest certain types of oral sex may be able to transmit HIV. However, statistical studies are based on groups of people, and individual specifics are rarely pinpointed. Increased statistical risk was found in homosexual males who had histories of swallowing semen, or having oral-anal contact.
Saliva contains such low concentrations of the virus, infection via saliva is unlikely. Saliva contains germ-killing chemicals which seem effective against HIV. Another factor that must be considered, however, is blood in the mouth. If a person is infected, his or her blood contains a high concentration of the virus and blood is far more infectious than saliva alone. The presence of blood in the mouth is a common event and not obvious. Blood in the mouth may originate from bites, abrasions, flossing, and bleeding gums. Kissing, if done roughly, can also create bleeding points in the mucous membranes of the gums and cheeks.
In many instances of HIV-infected homosexual males who continually wet-kissed (exchanged saliva) with their non-infected partners, no HIV transmission seems to have taken place.
However, many infected individuals at high-risk for infection are being told that kissing is totally safe. This advice may not be wise. The risk of catching HIV infection from wet kissing is close to zero, but it is not zero.
In 1985, a blood-screening test became available to blood testing centers. Though not 100% accurate, this test enables them to screen all blood donations for HIV. The test, however, had an unfortunate side effect. Individuals started donating blood in order to find out if they were HIV infected. Fortunately, now we have anonymous, free testing clinics in many locales rendering this practice unnecessary.
By current accounts, the blood test, which finds HIV antibodies, is close to perfect (reportedly 99.9% accurate), but it is not perfect. Also, in newly infected individuals, there is a "window" after HIV infection, but before the development of antibodies, when this test is useless. On limited evidence, this window now seems to be 3 to 6 months long. Thus it is possible that HIV infected blood could be collected during this window.
Despite these problems, the annual number of transfusion-related and HIV infections should soon become close to zero. However, the likelihood of catching HIV from a heterologous blood transfusion (blood from a person other than yourself) will remain an extremely remote possibility.
Intravenous needles (inserted into a vein) and hypodermic needles (needles inserted under the skin - usually into a muscle) and syringes (the plastic container attached to the needles) are all transmitters of HIV. You have no need to fear becoming infected from any new needle used in a doctor's office. Needles and most syringes used by doctors and hospitals are destroyed immediately after one use. Reusable injection guns, used in medical settings, have transmitted another blood borne disease, Hepatitis B. Therefore, improper use of these devices could theoretically transmit HIV.
The risk of medical needle use stems from reusing a needle, or sharing needles with another person. HIV is transmitted via the small amount of blood that remains in the needle or syringe after use.
Needle sharing habits are common among IV drug abusers. IV drug abusers commonly include people who inject heroin and/or cocaine into their veins. IV drug abusers also include individuals using steroids for body building who share IV needles with their friends. They may be using either intravenous or hypodermic needles. It is the practice of sharing contaminated needles and syringes, not the use of any particular drug, which holds the risk of HIV infection.
Health care workers have contracted HIV infections by accidentally sticking themselves with needles contaminated with HIV-infected blood or bodily substances.
Not all babies born to HIV-infected mothers catch HIV infection. Approximately one-half to one-third of babies born to HIV-infected mothers catch AIDS. Most children who have AIDS are diagnosed before the age of one year.
The problem with organ transplants is one of time. Fresh organs must be used immediately. There is little time to wait for a blood test to see if the donor, who is probably dead, was HIV-infected.
A number of females have been exposed to HIV by artificial insemination. Little follow-up information is available. Other sexually transmitted diseases have reportedly been transmitted by artificial insemination, including gonorrhea and Chlamydia.
Generally, with blood-borne diseases such as AIDS, transmission occurs only during invasive medical procedures, that is, medical procedures in which the health care worker's hands, and medical instruments, are inserted inside the body of the patient.
The risk stems from the health care worker cutting himself or herself and bleeding into the patient. Usually, the infections appear in clusters, with one health care worker infecting several patients before the situation is discovered.
There are a couple of cases in which HIV may have been transmitted with contact by feces and/or bodily secretions. In one instance, a mother caring for an HIV-infected infant (transfusion recipient) became infected. She frequently did not wear gloves and did not wash her hands immediately after frequent contact with the baby' s feces, blood, saliva, and nasal secretions.
Any of these instruments should be sterilized or disinfected before reuse.
After 10 years of documenting the AIDS epidemic, there are no known cases of AIDS or HIV infection being transmitted by casual social contact, not even among people living in the same household. In some instances, household members even shared toothbrushes with HIV-infected housemates without contracting HIV.
No medical or health care workers have contracted HIV from casual contact.
Insects are known to transmit both viral and bacterial disease to humans and other mammals. Insects commonly implicated in transmitting disease are mosquitoes, lice, bedbugs, ticks, fleas, and spiders. Insects are known to transmit both viruses and bacteria from animal reservoirs to humans, and probably visa versa.
Insects can be either biological transmitters or mechanical transmitters of disease. In biological transmitters, the cells inside the insect become infected by the germ. The insect thus becomes a germ-making factory. This situation occurs with malaria. The germ which causes malaria lives in the salivary gland of certain species of mosquitoes. No known insect becomes infected with HIV, thus no known insect is a biological transmitter of HIV.
Mechanical transmitters transmit germs from one host to another via mouthparts contaminated with infected blood. Mechanical transmission takes place when an insect is interrupted while feeding on one host and completes its meal on a second. There is no evidence that this has occurred with HIV.
In summary, insect transmission of HIV remains a remote theoretical possibility, but may not exist in the real world. If such transmission does exist, it is not epidemiologically important, that is, if HIV had to depend solely on insect transmission, the Human Immunodeficiency Virus would soon be extinct.