Below we talk about the ways HIV is spread -- and how it is not spread. Follow a link from the list below, then click the up arrow to bring you back to this point if you want to look at another link. Or, you can read straight through the entire document.
Activities That Allow HIV Transmission
Mother to child
Blood Transfusion (before March 1985)
Activities That Don't Allow HIV Transmission
Casual Contact/Shared Food
Saliva, Sweat, Tears
Other Transmission-Related Topics
Bodily Fluids: Infectious
Bodily Fluids: Not Infectious
Risk Assessment: Sample Scen-
Survival Outside the Body
Requirements For Transmission To Occur
Three conditions must be met for HIV transmission to occur:
HIV must be present;
Infection can only happen if one of the persons involved is infected with HIV. Some people assume that certain behaviors (such as anal sex) cause AIDS, even if HIV is not present. This is not true.
In sufficient quantity;
The concentration of HIV determines whether infection may happen. In blood, for example, the virus is very concentrated. A small amount of blood is enough to infect someone. A much larger amount of other fluids would be needed for HIV transmission.
And it must get into the bloodstream.
It is not enough to be in contact with an infected fluid to become infected. Healthy, unbroken skin does not allow HIV to get into the body; it is an excellent barrier to HIV infection. HIV can only enter through an open cut or sore, or through contact with the mucous membranes in the anus and rectum, the genitals, the mouth, and the eyes.
HIV Survival Outside The Body
Generally, when people ask the question, "How long can HIV survive outside the body?" they have come into contact with some body fluid that they think might contain HIV, and are worried about transmission. Almost always these questions are about casual contact, and we know the virus is not transmitted except during unprotected sex, sharing needles, or through significant and direct exposure to infected blood.
Length of time
The length of time HIV can survive outside the body depends on:
• the amount of HIV present in the body fluid;
• what conditions the fluid is subjected to
In a laboratory, HIV has been kept viable (able to infect) for up to 15 days, and even after the body fluid containing it had dried. However, these experiments involved an extremely high concentration of the virus which was kept at a stable temperature and humidity. These conditions are very unlikely to exist outside of a laboratory. HIV is very fragile, and many common substances, including hot water, soap, bleach and alcohol, will kill it.
Risk of transmission
The chances of becoming infected with HIV by handling a body fluid are extremely small, because that fluid will rarely have access to a person's bloodstream. However, anyone handling blood, semen or vaginal fluids should be careful to avoid touching them with broken skin or getting them into mucous membranes (such as those around the eye). Spills of blood should be mopped up, cleaned with soap and water, then cleaned with bleach. For maximum safety, the person cleaning the spill should also wear latex gloves, and should wash the hands thoroughly after the cleanup.
Exposure to air
Air does not "kill" HIV, but exposure to air dries the fluid that contained the virus, and that will destroy or break up much of the virus very quickly. The CDC reports that drying HIV reduces viral amount by 90-99 percent within several hours.
HIV can survive for several days in the small amount of blood that remains in a needle after use, so used needles are very risky for HIV transmission; they provide a direct path into the bloodstream. Ideally, used needles should never be reused, but if they are, they should always be cleaned with bleach or alcohol before re-use. See the section on Injection Drug Risk Reduction for additional information on this subject.
Where is HIV Found in the Body?
Looking at the first two conditions for HIV transmission (HIV present and in sufficient quantity), let's examine some of the so-called "bodily fluids" that can contain HIV.
Infectious "bodily fluids"
HIV can be transmitted from an infected person to another through:
• Blood (including menstrual blood)
• Vaginal secretions
• Breast milk
Blood contains the highest concentration of the virus, followed by semen, followed by vaginal fluids. Breast milk can also contain a high concentration of the virus, but in this situation, transmissibility depends on WHO and HOW. An adult can ingest a small amount of breast milk at no probable risk. But an infant, with its very small body and newly forming immune system, consumes vast quantities of breast milk relative to its body weight. Therefore an infant is at risk from breast milk, whereas an adult may not be.
Possibly infectious "bodily fluids"
HIV might be transmitted from an infected person to another from:
• Pre-seminal fluid (pre-cum)
Although it is difficult for researchers to analyze definitively, it is thought that HIV may be transmitted through pre-cum (this is a clear fluid that lubricates the urethra for semen). Pre-seminal fluid can contain semen or white blood cells, both of which have HIV in an infected person. So going back to conditions required for transmission, HIV can be present, but it is present in a relatively small amount, compared to semen or blood. Therefore, pre-seminal fluid presents a much lower risk for HIV transmission than ejaculate, but there is some risk, depending on where this fluid is going (as in all transmission situations).
Non-infectious "bodily fluids"
Activities That Allow HIV Transmission
Looking at the third condition for transmission (it must get into the bloodstream), there are three primary ways in which this can happen:
• Unprotected sexual contact
• Direct blood contact, including injection drug needles, blood transfusions, accidents in health care settings or certain blood products
• Mother to baby (before or during birth, or through breast milk)
Sexual Routes Of Transmission
Sexual intercourse (vaginal and anal): In the genitals and the rectum, HIV may infect the mucous membranes directly or enter through cuts and sores caused during intercourse (many of which would be unnoticed).
Oral sex (mouth-penis, mouth-vagina): The mouth is an inhospitable environment for HIV (in semen, vaginal fluid or blood), meaning the risk of HIV transmission through the throat, gums, and oral membranes is lower than through vaginal or anal membranes. There are however, documented cases where HIV was transmitted orally, so we can't say that getting HIV-infected semen, vaginal fluid or blood in the mouth is without risk.
Heterosexual transmission studies: It is evident, from epidemiological studies as well as common sense, that AIDS can be transmitted sexually between men and women. Several studies, usually with the female partners of hemophiliacs who have been infected, show that male to female sexual transmission does occur. This conclusion is supported by the statistics of women who have AIDS, whose only risk factor was sex with a man with AIDS or a man at risk for AIDS. Female to male sexual transmission seems to be less efficient, but it certainly does occur.
Non-Sexual Routes Of Transmission
Sharing injection needles: An injection needle can pass blood directly from one person's bloodstream to another. It is a very efficient way to transmit a blood-borne virus. Please see the section on Injection Drug Risk Reduction for more detailed information on injected drug use.
Needle sticks: A study of over 2,000 health care workers has been underway for several years to assess the risk of their exposure to people with AIDS. Over 1,000 of these workers had a needle stick accident with a needle that had been used on a person living with AIDS. The rest had some sort of mucous membrane exposure, such as being splashed in the face with blood or vomit.
Of all these people, only 21 show signs of being infected with HIV (as determined by the antibody test). One of these people was a nurse who had multiple needle stick accidents, including one where she tripped and fell on the depressor of a syringe full of blood, and the entire contents entered her body. Another was a lab worker who was working with a test tube of infected blood which broke and cut his finger, exposing the infected blood to his bloodstream. This study shows that AIDS is a difficult disease to get, and even the intimate exposure of these health care workers was not enough to infect them, except in the most extreme cases.
Blood transfusions: Since March 1985, all blood in the U.S. has been screened with the HIV antibody test. This practice has almost eliminated the risk of getting HIV through a blood transfusion.
Hemophilia treatments: Hemophilia is a genetic disease in which people (almost all men) lack the ability to clot blood. To control the condition, hemophiliacs take Factor VIII, a clotting factor. Each dose of Factor VIII comes from the pooled blood of many donors. Currently, over 90% of hemophiliacs in the U.S. have been infected with HIV because of receiving contaminated Factor VIII. Factor VIII is now heat-treated to kill the virus. In addition, there are new synthetic products that do not pose any risk for HIV and which accomplish the same function.
Other blood products: Besides whole blood, platelets (red blood cells) have transmitted the virus. Current blood screening, however, should prevent all but a very, very few cases. No other blood products are suspected of transmitting HIV. Gamma globulin or hepatitis B vaccine do not transmit HIV. Gamma globulin, however, can temporarily transmit HIV antibodies, although not the virus itself. These antibodies will disappear within a few months.
Mother to Child: It is possible for an HIV-infected mother to pass the virus directly before or during birth, or through breast milk. Approximately 20% of babies born to HIV-positive women who undertake no transmission-reduction measures will be infected with HIV. Taking AZT during the later stages of pregnancy and delivery reduces this probability to 5% - 8%. Recent studies presented at the 12th World AIDS Conference indicate that transmission is reduced to less than 2% if a caesarian section (c-section) is performed prior to labor, incombination with AZT therapy. Other studies are being conducted to determine whether vaginal cleansing and use of antiviral vaginal suppositories prior to birth are effective in reducing mother-to-child, or "perinatal," transmission.
Breast milk contains HIV, and while small amounts of breast milk do not pose significant threat of infection to adults, it is a viable means of transmission to infants. The United Nations presented a recommendation at the 12th World AIDS Conference suggesting that infected mothers not breast feed their infants. Despite use of AZT by the mother, approximately 5% of vertical transmission occurs via breast milk.
Donor insemination: Donor semen is checked for HIV antibodies when the semen is collected. The semen is then frozen. The donor is required to come back after six months for a second HIV test, to confirm the initial HIV screening. The semen is not used before the procedure is completed.
HIV Is NOT Transmitted By:
HIV is not transmitted by mosquitoes, flies, ticks, fleas, bees or wasps. If a bloodsucking insect bites someone with HIV, the virus dies almost instantly in the insect's stomach (as it digests the blood). HIV can only live in human cells.
Mosquitoes cannot transmit HIV for two reasons:
• The mosquito draws blood and injects saliva. The blood from one person is not injected into the mosquito's next victim.
• HIV dies in the mosquito's body. People sometimes are confused because malaria actually reproduces inside the mosquito's digestive track, using the insect as part of its life cycle. HIV does not.
These facts are confirmed by lookng at infection patterns. In areas where mosquitoes are common and where HIV is prevalent, the distribution of AIDS cases in the population is not different from other areas. If mosquitoes transmitted HIV, we would be seeing a disproportionate number of children and elderly infected in those areas.
Casual Contact/Sharing dishes or food
HIV is not transmitted through casual, every day contact. Since HIV is not transmitted by saliva, it is impossible to get it through sharing a glass, a fork, a sandwich, or fruit.
Three studies of household contacts, in the U.S., Europe, and Africa, have shown that AIDS is not casually transmitted by normal activities, even when people are in close living arrangements. All the studies examined households where someone had AIDS to see if any of the other members in that household had become infected (sexual contact was excluded). Many of these households included a small child as the one who has AIDS. These children continued to play with siblings in the manner that children play: wrestling, fighting, spitting, sharing food and clothes, and many other activities. No other member of any of the households shows any sign of being infected. This study shows that AIDS is a difficult disease to get, and that even the intimate exposure common among small children living together is not sufficient to transmit the virus.
Sterilized needles are always used in taking blood from donors, so HIV is not spread in this manner.
Swimming pools and hot tubs
The chemicals used in swimming pools and hot tubs would instantly kill any HIV, if the hot water hadn't killed it already.
Humans are the only animals that can harbor HIV. People sometimes think they can get HIV from pets, because some animals carry viruses that produce similar immune deficiencies in their own species, e.g. FIV, feline immunodeficiency virus, in cats, and SIV, simian immunodeficiency virus, in some types of monkeys. However, FIV cannot be transmitted to people, nor can HIV be transmitted from humans to pets such as cats and dogs. (An exception is chimpanzees used in research that have been infected with HIV. Their blood poses a risk to researchers working with them). There have been two reported cases of transmission of SIV to researchers, but no one knows if the virus will cause disease in them.
Contact with saliva, tears, sweat, feces or urine
Transmission can only occur when a sufficient amount of HIV enters the bloodstream, through cuts or mucous membranes. These "bodily fluids" either contain no HIV or it exists in a quantity too small to result in transmission.
HIV is not transmitted by saliva. There is a great deal of evidence to support this fact. In a study of 79 men with AIDS, the virus could be found in the saliva of only one. This man had PCP, thrush, and other mouth and throat lesions. Even in this man, the level of virus found in his saliva was 10,000 times less than the level in his blood. To this study we can add the evidence of the countless numbers of people who have had saliva contact with people with AIDS or others who have been infected. This contact has occurred through kissing, sharing food, sharing joints, and many other means. We can find no evidence that these activities have transmitted the virus even a single time. Recent findings suggest that saliva contains an enzyme which kills HIV. Certainly there is a lot at work in the mouth combining to make the mouth an inhospitable site for the virus: acids, enzymes, friction, dilution, air, and more.
Becoming infected with HIV during a sexual assault is very unlikely. Despite 45,000 rape crimes per year, in 1989 there had not been a single report of a female infection as a result of sexual assault. No data about male/male rape was available. If the person that committed the assault does not have the AIDS virus in his body, it is impossible to become infected from him. Even if the rapist is HIV positive, a person is still very unlikely to become infected during a rape.
Why is transmission unlikely?
First, the risk of infection from a one-time exposure is low. Repeated sexual contact with an infected person or exposure to many infected men is more likely in becoming infected with HIV.
Also, many assailants experience sexual dysfunction during the crime and do not ejaculate. It is also statistically unlikely that the attacker is HIV positive.
What are the risks?
A one-time sexual assault does not dramatically increase the risk of becoming infected with HIV. A person at low risk before a sexual assault is still at low risk after. If you need to find out whether you at risk, call an AIDS hotline. Within California, call the San Francisco AIDS Foundation's California AIDS Hotline toll free at 800/367-AIDS. Outside California, call the CDC National AIDS Hotline toll free at 800/342-AIDS.
What type of assault is risky?
Any assault where the assailant's blood or semen has access to the person's bloodstream is risky. If the assault is violent and the person bleeds, this may be more likely. Anal penetration is the highest risk; vaginal penetration is somewhat less risky; semen in the mouth presents the smallest risk. Ejaculation in any of these cases increases the risk significantly.
Testing issues for victims of sexual assault
For legal purposes only, it may be a good idea for a person who has been raped to be tested immediately. It can establish that the person was not infected at the time of the assault. If s/he is HIV negative and later tests positive for HIV, there may be a basis for legal action beyond the assault charge.
For the purpose of learning their HIV status, the AIDS antibody test, taken after three to six months, is the most reliable way for the person to learn if s/he has been infected with HIV. Although it may be extremely difficult for a person to wait that long, there is little sense in taking a test sooner, and we would not recommend the PCR test in these circumstances. The test is reliable for most people after three months, but after six months one can be most certain about the result.
NOTE: If you or someone you know was the victim of an assault crime within the last 72 hours, it is important that evidence collection happen immediately. Every California county has some hospital-based program that is linked with the police. A person who's been raped can call the police, without having to file a report, to learn about the availability of these services. The AIDS Foundation's referral database lists California agencies who can assist victims of sexual assault (type in the keyword phrase: sexual assault).
Transmission Through Tattooing, Piercing, Acupuncture, Electrolysis, and Shaving
What is the risk?
Any procedure in which a needle or razor is used on more than one person involves a theoretical risk of HIV transmission because of the possibility of infected blood on the instrument. However, the risk can be reduced or eliminated through routine sterilization procedures. There are no documented cases in the United States of someone becoming infected through tattooing or piercing.
Tattoo artists, piercers, hairdressers and barbers, massage therapists, manicurists and pedicurists, and acupuncturists are all defined by the Centers for Disease Control (CDC) as "personal service workers" (PSWs). The CDC has established universal precautions for PSWs, similar to those for health care workers, which are designed to protect both the workers and their customers from HIV and other blood-borne illnesses such as hepatitis. The guidelines state that any instruments designed to penetrate the skin such as tattoo or acupuncture needles either should be used only once and discarded, or should be thoroughly cleaned and sterilized after each use.
If you are worried about the risks of such procedures, you should discuss infection control precautions with the provider. In the case of tattoos and acupuncture, you may also provide your own fresh needles to ensure sterility.
In California, establishments that provide personal services may be regulated locally, so anyone who has further concerns about the procedures in an establishment should call the local department of public health.
Risk Assessment: Sample Scenarios
Transmission questions can often not be answered in a black-or-white fashion, i.e. "this is always risky, that is never risky." The answer will usually involve two questions, going back to our conditions necessary for HIV transmission to occur:
What is the substance ("body fluid") and can it possibly contain HIV in sufficient quantity to cause infection?
Where is it going in the body?
The following are some examples of common situations and how the information about transmission can help you assess your risk.
A man performed oral sex without a condom on another man. His partner did not ejaculate in his mouth. He doesn't know his partner's HIV status.
Was the virus present? We don't know, because we don't know if the partner was infected.
Was there enough concentration? There was no semen involved. It is possible that there was pre-ejaculate fluid present, which may involve some risk.
Could HIV make it into the bloodstream? If HIV were present, it could enter the body by infecting mucous membranes in the mouth or through open cuts or sores.
What was the level of risk? If the partner was not HIV positive, there is no risk. On the other hand, if the partner were HIV positive, there would be a low level of risk due to the possibility of contact with pre-ejaculate fluid. Considering that there are very few cases of transmission through oral sex reported, the risk in this situation is not very high.
If the man is very worried about the incident, it is important for him to remember that there was some risk involved, but that the risk is not very high. If he feels that there was no risk at all and that he can continue practicing unprotected oral sex, it is important for him to know that although the risk was low, it is still there.
A woman has found out that her previous drug partner is HIV-positive. They only shared needles once. She thinks that he got infected after they stopped seeing each other.
Was the virus present? We don't know because we don't know when he became infected.
Was there enough concentration? Yes. HIV in blood may be transmitted if two people share needles.
Was there a path of infection? Yes. Sharing needles provides a direct path for HIV to reach the bloodstream.
What was the level of risk? High, if her partner was already infected when they shared a needle.
It is important for her to be aware that there is a possibility for high risk.
A woman is concerned about getting HIV from a co-worker. She accidentally drank from his cup. She thinks that he may be gay.
Was the virus present? We don't know. We cannot judge whether a person is infected or not based on his or her sexual orientation.
Was there enough concentration? No. Even if he's infected, she would have been in contact with his saliva. Saliva does not transmit HIV.
Was there a path of infection? In this case, this question is irrelevant because of the answer to the previous two questions. Speculating about open cuts in the mouth would just cloud the issue.
What was the level of risk? There was NO risk. She cannot get HIV from drinking from the same cup, even if the person is infected.
A few words about risk, sex and guilt
In our daily lives we take many risks. When we drive, cook, or climb a ladder, there is some risk involved. In some cases, such as driving, the risk involved may be quite high. However, in most instances we get used to conducting our daily risky activities without letting the risk stop us. (In some cases, we reduce the risk by using protective measures such as seat belts, and pot holders).
When it comes to AIDS, though, most people deal with risk in a different way. Although some people can continue having sex without problems after learning about safe sex, many others feel very scared and anxious about catching the virus, even if they know about condoms and other protective measures. Interestingly, the risk of AIDS for an average person is many times smaller than the risk of dying in a car accident, or being struck by lightning.
The anxiety can be related to feelings that people have about sexuality and drugs. Feelings of guilt, for example, may be translated into fear for AIDS. This fear is real. However, people may not realize that it has more to do with anxiety about their sexual behavior than with their risk for AIDS.