Catching AIDSIn 1979, when the Human Immunodeficiency Virus (HIV) was rare, in orderto become infected, a large number of sexual contacts was generally required. HIV is no longer rare in the U.S. population. According to current scientific guesstimates, I million U.S. citizens are currently infected with the HIV virus. If this figure is correct, then one out of approximately every 270 people in the United States is infected. AIDS is not evenly distributed throughout the United States. Pockets of high concentration exist among specific sub-populations and in certain geographical locations. Thus, again assuming that the I million guesstimate is correct, some areas of the United States many have only one infected individual out of thousands, while otherareas may have one infected individual out of dozens.
Unfortunately, up to now, most estimates of the number of HIV-infectedpeople have been overblown. As early as 1983, selected scientists, andconsequently the media, trumpeted estimates of 1 to 3 million. At the time,these estimates were exaggerated. Now, however, the AIDS epidemic is 10years old, and scientists have tabulated over 200,000 total registeredAIDS 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-infectedcells) during exposure. The more viruses present, the better the chanceof one or more viruses succeeding in finding a host cell and replicating.
Viruses are not able to enter the body through intact skin. Thereforeviruses must enter the body through an open wound(s) or one of a numberof possible body openings. Most of these body openings contain mucous membranes.Mucous membranes are thin tissues which protect many openings and passagesin the human body. These membranes secrete mucus. Which contains anti-germchemicals and keeps the surrounding tissues moist. There are mucous membranesin the mouth, inside the eyelids, in the nose and air passages leadingto 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 membraneand enter the tiny blood vessels inside.
The mucous membranes of the eyes and mouth are often doorways into ourbodies for highly infectious viruses such as the flu. You can catch theflu from a person in the following manner: the person coughs in his orher hand, you shake hands soon afterward, and then your virus-carryinghand 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 ispresent in the sputum of an infected person. (Sputum is the substance expelledby coughing or by clearing the throat. Concentration is the number of virusesper unit of volume.) Coughing forces many viruses out of the lungs andinto the air or onto the sick person' s hand or handkerchief. The flu viruseasily crosses the mucous membrane.
The danger with AIDS is very different. With AIDS, the major infectionsites are the bloodstream and the central nervous system. While HIV-carryingmacrophages (roving white blood cells that engulf invaders, but are susceptibleto HIV infection) are found in the connective tissues of the lung and inoral and mucous membranes, the number of viruses present does not seemgreat. Thus, HIV is present in low concentrations, if at all, in salivaand sputum. So coughing should not expel a large quantity of HIV, if any.Apparently, HIV cannot cross the mucous membrane very easily, and largeconcentrations of HIV are probably necessary.
In an infected person, HIV is found in any body fluid or substance whichcontains lymphocytes (T4-cell and company). Substances containing lymphocytesinclude: 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 thesubstance is capable of transmitting HIV infection. All of these substancesare capable, in theory, of transmitting disease; but in reality, the mostdangerous substances seem to be blood, semen, and cervical and vaginalsecretions, and perhaps feces. Despite a lot of looking, no one has beenable to find a clear cut case of saliva causing transmission, althoughkissing theoretically could. See "Kissing."
The concentration of HIV in these substances is very important whenit comes to infectivity. (Concentration is "number of viruses perunit of volume") If a substance contains a high concentration, thatis, a lot of viruses, then it is more likely HIV can be transmitted bythe substance. Below a certain concentration of viruses, the substancecan not effectively transmit HIV infection.
The importance of concentration is illustrated by the situation withsperm and pregnancy. If a male's semen contains fewer than 20 million spermcells per milliliter (cubic centimeter), than it is unlikely that the malewill be able to impregnate a female. Similarly, if the concentration ofa virus is too low in sputum or any other substance, then it is unlikelyto transmit infection.
HIV is also in pre-ejaculate fluid. Pre-ejaculate fluid oozes from thetip 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 highas the concentration of HIV in semen and blood, but, these substances areinfectious and can transmit HIV infection.
In theory, saliva can transmit HIV infection but, so far, it doesn'tseem to have happened in real life. Kissing is discussed in more detailin 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 substanceare capable of remaining infectious until these substances dry up, dependingon circumstances, probably a matter of minutes or hours. If any of thesesubstances 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 sexualcontact, transfusions of blood and blood products, sharing contaminatedintravenous (IV) needles, and passage of the virus from mother to unbornchild.
Being exposed to a virus does not mean that a person is going to catchthe virus. Exposure does not necessarily mean transmission. For example,when a person with the flu sneezes in the face of another person, the sneezerecipient may or may not contract the flu. Any number of factors contributeto 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 anusof another person. From the body's viewpoint, anal intercourse is not agreat idea. The anus is biologically designed for the excretion of feces.Evidently, medical disorders can arise from frequent and/or rough analintercourse.
During anal intercourse, the receptive partner is the partner at greatestrisk of catching HIV. The receptive partner is the person whose anus isbeing penetrated. This high risk for receptive partner exists whether thereceptive partner is male or female.
Previously, it was thought that anal intercourse transmitted HIV infectionbecause, during anal intercourse, the penis opened bleeding wounds insidethe receptive partner's anus. These bleeding wounds were thought to bethe doorway by which HIV directly entered the bloodstream to reach andinfect T4-cells.
Now, it appears that the presence of bleeding wounds in the anus isnot necessary for HIV transmission to take place. Macrophages are present,roving over the surfaces of the anus. HIV may infect these macrophagesdirectly. Also, HIV is probably able to cross the mucous membrane and enterthe tiny blood vessels inside. No damage to the wall of the anus may benecessary for HIV transmission to take place. According to a statisticalstudy, rectal douching after anal intercourse increases the risk of HIVinfection.
"Fisting" is the insertion of the fingers, or the entire handinto the anus. It might be considered a form of anal intercourse. Accordingto a statistical study, fisting carries a slight risk for the insertivepartner. There is little risk for the receptive partner. The risk to theinsertive partner probably comes from contact with feces or with bloodfrom the anus. People's hands often have small, invisible wounds aroundthe cuticles of the fingernails; these may provide doorways into the bodyfor the virus. Or, there could be an anus-to-hand to mouth transmissionof the virus. This increased risk for the insertive partner could be astatistical quirk. If the risk does exist, no one yet knows its true cause.
Apparently, HIV transmission from males to females occurs more effectivelythan from females to males. This greater risk seems to be true for mostsexually transmitted diseases: the female is at greater risk. ("Receptivepartner" can be substituted for "female" in case of homosexualsex) A male's exposure to the female (or receptive partner) is fleeting;but the male leaves potentially contaminated semen in the vagina. Usuallythe semen remains in the female long after intercourse is over. The longera person is exposed to germs, the more likely he or she is to catch thedisease.
Male to female: If the male is infected, he deposits HIV-infected semeninside the female's vagina. Again, previously it was thought that insidea female's vagina, small wounds and bleeding may occur during sex or fora 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 conditionin females, which makes the surface of the cervix and the vagina more likelyto bleed. Cervicitis may be caused by IUD contraceptives devices and bysexually transmitted diseases such as gonorrhea, syphilis, and Chlamydiainfection.
Females probably do not have an increased risk for catching HIV duringmenstruation. Menstrual bleeding is actually the shedding of the tissuesof the uterus (womb). Menstrual blood flows from the uterus, through thecervix, and into the vagina. There is no vaginal wound for entry by HIV.
Again, it should be noted, that the current consensus is that woundsmay not be necessary, since HIV may directly infect macrophages, whichrove the mucous membrane surfaces. Also, HIV may be able to directly crossthe mucous membrane and enter the blood vessels therein.
The vaginal secretions contain anti-germ chemicals. The vagina, beingdesigned to accept foreign objects, has substantial immune defenses. Thismay explain why vaginal intercourse apparently does not transmit HIV infectionas effectively as anal intercourse.
Female to male: Males can catch HIV from infected females. The methodof transmission is not clear. It may be possible for HIV infection to comefrom menstrual blood or from contact with a female's vaginal or cervicalsecretions.
The concentration of HIV in these substances does not seem very high(compared with blood and semen), still the concentration is sufficientfor HIV transmission to take place. Small amounts of blood may also bepresent in the vagina due to rough sexual intercourse or to other vaginalconditions.
In males, the doorway for HIV into the body may be very small woundson the head of the penis, the mucous membranes lining the urethra (the"eye" of the penis is the opening of the urethra), or the glandswhich intersect the urethra at the base of the penis.
The condition of the cells lining the urethra may be important in malesusceptibility to infection. The health of the cells may be affected bySTDs (sexually transmitted diseases) or other irritants.
Once inside the mouth, HIV may penetrate the mucous membranes of themouth, or enter the bloodstream via a number of possible doorways, includingany small wound such as cold sores, bleeding gums (inflicted by toothbrushor 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'smouth to the other person's penis, vagina, or anus. With HIV, this eventis possible in theory, but seems unlikely owing to HIV's low concentrationin saliva.
Blood, a highly infectious substance, may be present in the either partner'smouth, the male's urethra, the female's vagina, in a male's or female'sanus from sores or from rough sexual intercourse, and/or in the female'svagina during menstruation.
There are no proven cases of individual people catching HIV from oralsex, but several suspected cases have come into light. Several homosexualmales 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 certaintypes of oral sex may be able to transmit HIV. However, statistical studiesare based on groups of people, and individual specifics are rarely pinpointed.Increased statistical risk was found in homosexual males who had historiesof swallowing semen, or having oral-anal contact.
Saliva contains such low concentrations of the virus, infection viasaliva is unlikely. Saliva contains germ-killing chemicals which seem effectiveagainst HIV. Another factor that must be considered, however, is bloodin the mouth. If a person is infected, his or her blood contains a highconcentration of the virus and blood is far more infectious than salivaalone. 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 bleedinggums. Kissing, if done roughly, can also create bleeding points in themucous 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 transmissionseems to have taken place.
However, many infected individuals at high-risk for infection are beingtold that kissing is totally safe. This advice may not be wise. The riskof catching HIV infection from wet kissing is close to zero, but it isnot 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 donationsfor HIV. The test, however, had an unfortunate side effect. Individualsstarted donating blood in order to find out if they were HIV infected.Fortunately, now we have anonymous, free testing clinics in many localesrendering this practice unnecessary.
By current accounts, the blood test, which finds HIV antibodies, isclose to perfect (reportedly 99.9% accurate), but it is not perfect. Also,in newly infected individuals, there is a "window" after HIVinfection, but before the development of antibodies, when this test isuseless. On limited evidence, this window now seems to be 3 to 6 monthslong. Thus it is possible that HIV infected blood could be collected duringthis window.
Despite these problems, the annual number of transfusion-related andHIV infections should soon become close to zero. However, the likelihoodof catching HIV from a heterologous blood transfusion (blood from a personother than yourself) will remain an extremely remote possibility.
Intravenous needles (inserted into a vein) and hypodermic needles (needlesinserted under the skin - usually into a muscle) and syringes (the plasticcontainer attached to the needles) are all transmitters of HIV. You haveno need to fear becoming infected from any new needle used in a doctor'soffice. Needles and most syringes used by doctors and hospitals are destroyedimmediately after one use. Reusable injection guns, used in medical settings,have transmitted another blood borne disease, Hepatitis B. Therefore, improperuse of these devices could theoretically transmit HIV.
The risk of medical needle use stems from reusing a needle, or sharingneedles with another person. HIV is transmitted via the small amount ofblood that remains in the needle or syringe after use.
Needle sharing habits are common among IV drug abusers. IV drug abuserscommonly include people who inject heroin and/or cocaine into their veins.IV drug abusers also include individuals using steroids for body buildingwho share IV needles with their friends. They may be using either intravenousor hypodermic needles. It is the practice of sharing contaminated needlesand syringes, not the use of any particular drug, which holds the riskof HIV infection.
Health care workers have contracted HIV infections by accidentally stickingthemselves with needles contaminated with HIV-infected blood or bodilysubstances.
Management of Occupational Exposures to HIV
Not all babies born to HIV-infected mothers catch HIV infection. Approximatelyone-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 mustbe used immediately. There is little time to wait for a blood test to seeif 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 diseaseshave reportedly been transmitted by artificial insemination, includinggonorrhea and Chlamydia.
Generally, with blood-borne diseases such as AIDS, transmission occursonly during invasive medical procedures, that is, medical procedures inwhich the health care worker's hands, and medical instruments, are insertedinside the body of the patient.
The risk stems from the health care worker cutting himself or herselfand bleeding into the patient. Usually, the infections appear in clusters,with one health care worker infecting several patients before the situationis discovered.
There are a couple of cases in which HIV may have been transmitted withcontact by feces and/or bodily secretions. In one instance, a mother caringfor an HIV-infected infant (transfusion recipient) became infected. Shefrequently did not wear gloves and did not wash her hands immediately afterfrequent contact with the baby' s feces, blood, saliva, and nasal secretions.
Any of these instruments should be sterilized or disinfected beforereuse.
After 10 years of documenting the AIDS epidemic, there are no knowncases 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 housemateswithout 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 humansand other mammals. Insects commonly implicated in transmitting diseaseare mosquitoes, lice, bedbugs, ticks, fleas, and spiders. Insects are knownto transmit both viruses and bacteria from animal reservoirs to humans,and probably visa versa.
Insects can be either biological transmitters or mechanical transmittersof disease. In biological transmitters, the cells inside the insect becomeinfected by the germ. The insect thus becomes a germ-making factory. Thissituation occurs with malaria. The germ which causes malaria lives in thesalivary gland of certain species of mosquitoes. No known insect becomesinfected with HIV, thus no known insect is a biological transmitter ofHIV.
Mechanical transmitters transmit germs from one host to another viamouthparts contaminated with infected blood. Mechanical transmission takesplace when an insect is interrupted while feeding on one host and completesits meal on a second. There is no evidence that this has occurred withHIV.
In summary, insect transmission of HIV remains a remote theoreticalpossibility, but may not exist in the real world. If such transmissiondoes exist, it is not epidemiologically important, that is, if HIV hadto depend solely on insect transmission, the Human Immunodeficiency Viruswould soon be extinct.