Why are some bodily fluids more of an infection risk than others?

Why are some bodily fluids more of an infection risk than others?

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Whilst on a recent refresher course it was highlighted that when considering risk of exposure to infection from bodily fluids we should be aware of two distinct risk levels:

High Risk:

  • Blood
  • Semen
  • Vaginal Secretions
  • Diarrhea

Low Risk:

  • Saliva
  • Vomit
  • Urine
  • CSF (Cerebrospinal fluid)

Why is it that some bodily fluids are a greater infection risk than others? Is it related to the fluids themselves or the species of pathogen that are located within them?

This is just about where the pathogens can be found that are dangerous to people.

Vomit is highly acidic and less accommodating to microbe growth. Similarly saliva has many immune components in it as well as digestive enzymes that keep most microorganisms down.

Urine and CSF are actually quite sterile as they come from environments that are highly filtered - the kidney is an osmotic processor that essentially is a molecular filter and does not allow cells to pass, the spine is highly insulated from the blood and other direct exposure to microorganisms.

Compare that with the 'dangerous' list and you have organs that are open to human pathogens. Venerial disease like HPV is so common that what - about 1 in 5 people under a certain age carry it. That is a pretty high expectation of a biohazard. most infections and viruses are blood bourne - influenza, cold, as well as any bacterial infections.

Feces is always a dangerous thing to handle as the digestive tract is rich in nutrients and essentially directly open to external bacteria and fungi. (and its not acidified like the stomach). Also parasites like tape worms and other multicelled animals! yum!

Diarrhea is often caused by an infection of some sort, so its just more likely a hazard, but feces is always a place where you might find a pathogen.

This is not to say that the 'safe' list is totally safe. Its just less likely to bear disease causing agents.

The Truth About Hydration: 5 Myths and 5 Facts

Find out how much water you really need to drink each day, whether you can overdose on H2O, and more.

Hydration is one of those things you know you should be on top of, but you may not fully understand why.

“Hydration is important because our bodies really function [best with] adequate water balance,” says Shilpi Agarwal, MD, a board-certified family medicine physician in Washington, DC, and the author of The 10-Day Total Body Transformation. “Most organ functions require water in the right proportion to work — meaning your muscles, heart, and kidneys all need water and also need the body to be adequately hydrated in order to work properly.”

And what about dehydration, to some a scary word that may be associated with health issues big and small? “Mild dehydration can lead to dizziness, fatigue, flushed skin, headache, impaired physical performance, and confusion,” explains Malina Malkani, RDN, who lives in Rye, New York, and is the creator of Solve Picky Eating, a program for parents of finicky eaters. If unaddressed, more extreme dehydration can even cause problems like labored breathing, increased body temperature, poor blood circulation, and seizures, Malkani adds. And according to the Harvard T.H. Chan School of Public Health, dehydration can contribute to urinary tract infections and kidney stones.

To clear up confusion around hydration and dehydration, here are 10 things you must know to keep your health in tip-top shape.

Types of Microbes

There are five major categories of infectious agents: Viruses, bacteria, fungi, protozoa, and helminths.


Viruses are tiny, ranging in size from about 20 to 400 nanometers in diameter (see page 9). Billions can fit on the head of a pin. Some are rod shaped others are round and 20 sided and yet others have fanciful forms, with multisided “heads” and cylindrical “tails.”

Viruses are simply packets of nucleic acid, either DNA or RNA, surrounded by a protein shell and sometimes fatty materials called lipids. Outside a living cell, a virus is a dormant particle, lacking the raw materials for reproduction. Only when it enters a host cell does it go into action, hijacking the cell’s metabolic machinery to produce copies of itself that may burst out of infected cells or simply bud off a cell membrane. This lack of self-sufficiency means that viruses cannot be cultured in artificial media for scientific research or vaccine development they can be grown only in living cells, fertilized eggs, tissue cultures, or bacteria.


An electron micrograph of an influenza virus particle, showing details of its structure.

Viruses are responsible for a wide range of diseases, including the common cold, measles, chicken pox, genital herpes, and influenza. Many of the emerging infectious diseases, such as AIDS and SARS, are caused by viruses.


Bacteria are 10 to 100 times larger than viruses and are more self-sufficient. These single-celled organisms, generally visible under a low-powered microscope, come in three shapes: spherical (coccus), rodlike (bacillus), and curved (vibrio, spirillum, or spirochete).

Most bacteria carry a single circular molecule of DNA, which encodes (or programs) the essential genes for reproduction and other cellular functions. Sometimes they carry accessory small rings of DNA, known as plasmids, that encode for specialized functions like antibiotic resistance. Unlike more complex forms of life, bacteria carry only one set of chromosomes instead of two. They reproduce by dividing into two cells, a process called binary fission. Their offspring are identical, essentially clones with the exact same genetic material. When mistakes are made during replication and a mutation occurs, it creates variety within the population that could—under the right circumstances—lead to an enhanced ability to adapt to a changing environment. Bacteria can also acquire new genetic material from other bacteria, viruses, plants, and even yeasts. This ability means they can evolve suddenly and rapidly instead of slowly adapting.


E. coli bacteria directly transferring genetic material via a pilus (the thin strand connecting the two).

Bacteria are ancient organisms. Evidence for them exists in the fossil record from more than 3 billion years ago. They have evolved many different behaviors over a wide range of habitats, learning to adhere to cells, make paralyzing poisons and other toxins, evade or suppress our bodies’ defenses, and resist drugs and the immune system’s antibodies. Bacterial infections are associated with diseases such as strep throat, tuberculosis, staph skin infections, and urinary tract and bloodstream infections.

Other Infectious Agents

The other three major types of infectious agents include fungi (spore-forming organisms that range from bread mold to ringworm to deadly histoplasmosis), protozoa (such as the agents behind malaria and dysentery), and helminths (parasitic worms like those that cause trichinosis, hookworm, and schistosomiasis).

A newly recognized class of infectious agents—the prions, or proteinaceous infectious particles𠅌onsist only of protein. Prions are thought to cause variant Creutzfeldt-Jakob disease in humans and “mad cow disease” in cattle. These proteins are abnormally folded and, when they come in contact with similar normal proteins, turn them into prions like themselves, setting off a chain reaction that eventually riddles the brain with holes. Prions evoke no immune response and resist heat, ultraviolet light, radiation, and sterilization, making them difficult to control.


Grand Prismatic Spring, a geothermal hot spring in Yellowstone and home to microbes that have adapted to this extreme environment.

Development of Infection

Infectious diseases are usually caused by microorganisms that invade the body and multiply. There are many types of infectious organisms (see also Overview of Infectious Disease).

The following are some examples of how microorganisms can invade the body:

Through the mouth, eyes, or nose

Through contaminated medical devices

People can ingest microorganisms by swallowing contaminated water or eating contaminated food. They may inhale spores or dust or inhale contaminated droplets coughed or sneezed out by another person. People may handle contaminated objects (such as a doorknob) or come into direct contact with a contaminated person and then touch their eyes, nose, or mouth.

Some microorganisms are spread through body fluids such as blood, semen, and stool. Thus, they can invade the body through sexual contact with an infected partner. They also can enter through nonsexual contact with body fluids, such as while providing personal care or medical services.

Human and animal bites and other wounds that break the skin can allow microorganisms to invade the body. Infected insects and ticks can spread diseases when they bite.

Microorganisms can also adhere to medical devices (such as catheters, artificial joints, and artificial heart valves) that are placed in the body. Microorganisms may be present on the device when it is inserted if the device was accidentally contaminated. Or infecting organisms from another site may spread through the bloodstream and lodge on an already implanted device. Because implanted material has no natural defenses, the microorganisms can easily grow and spread, causing disease.

After invading the body, microorganisms must multiply to cause infection. After multiplication begins, one of three things can happen:

Microorganisms continue to multiply and overwhelm the body’s defenses.

A state of balance is achieved, causing chronic infection.

The body—with or without medical treatment—destroys and eliminates the invading microorganism.

Invasion by most microorganisms begins when they adhere to cells in a person’s body. Adherence is a very specific process, involving "lock-and-key" connections between the microorganism and cells in the body. Being able to adhere to the surface of a cell enables microorganisms to establish a base from which to invade tissues.

Whether the microorganism remains near the invasion site or spreads to other sites and how severe the infection is depend on such factors as the following:

Person to person spread

This is the most common way that we get an infectious disease. Germs can spread from person to person through:

  • the air as droplets or aerosol particles
  • faecal-oral spread
  • blood or other body fluids
  • skin or mucous membrane contact
  • sexual contact.

Some infections can be spread in more than one way.

Through the air as droplets or aerosol particles (airborne)

Some infections are spread when an infected person talks, coughs or sneezes and the small droplets they produce contain germs. The droplets travel a short distance before falling. The droplets may be breathed in by people who are near, or may fall and contaminate an object or surface. Spread can also occur by touching the nose or mouth with hands contaminated by the droplets. Examples of diseases spread by droplet:

Other infections are spread when an infected person talks, breathes, coughs or sneezes tiny particles that contain germs into the air. These are called small particle aerosols. Since these aerosol particles are tiny, they can stay suspended in the air for hours and be breathed in by other people. Examples of aerosol spread:

Some germs can be spread by both droplets and aerosols eg, the flu.

Through faecal-oral spread

Some infections are spread when tiny amounts of faeces (poo) from an infected person are taken in by another person by their mouth. The germs may be passed directly from infected hands to the mouth or indirectly through objects, surfaces, food or water contaminated with poo. Examples of diseases spread this way:

Through blood or other body fluids

Some infections are spread when body fluids such as blood, saliva, urine (wees), faeces (poos) or semen come into direct contact with an uninfected person through kissing, sexual contact or through a needlestick injury. Examples of diseases spread through body fluids:

Through contact with skin or mucous membrane

Some infections are spread directly when skin or mucous membrane (the thin lining of parts of the body such as nose, mouth, genitals) comes into contact with the skin or mucous membrane of an infected person. Infections may be spread indirectly when the skin comes in contact with a contaminated object. Examples of diseases spread this way:

Through sexual contact

Sexually transmitted infections (STIs) are most commonly transmitted by sexual contact. This means through vaginal, anal or oral sex.

Examples of sexually transmitted infections are:

Special precautions when taking chemo by mouth

Oral chemo, or chemo you take by mouth and swallow, is usually taken at home. These drugs are as strong as other forms of chemo, and many are considered hazardous. There are usually special precautions for storing and handling oral chemo drugs. You might be told to be careful not to let others come into contact with it or your body fluids while taking it and for a time after taking it. Sometimes you need to wear gloves when touching the pills or capsules. Some drugs have to be kept in the bottle or box they came in. And some drugs and the packages they come in need to be disposed of in a certain way. Some might have to be taken back to the drug store to be thrown away safely. If you are taking an oral chemo drug, talk to your cancer care team about any special precautions needed at home. To learn more, see Getting Oral or Topical Chemotherapy.

Why are some bodily fluids more of an infection risk than others? - Biology

Objective : Students will understand the dynamics of the transmission of diseases by taking part in a "hands-on" simulation.

Introduction : Begin with a discussion of how epidemics begin, and how they spread. Give some examples from history, such as the Plague, AIDS, Ebola, H1N1, or make reference to movies such as Outbreak. Tell students, or have them listen to, the fascinating story of Typhoid Mary, and describe the role of the CDC (Center for Disease Control). Discuss the concepts of a biohazard, quarantine, epidemic and pandemic. Explain how today's simulation will work. Ask why local epidemics can more easily become pandemics in the modern world (speed of travel, open borders, large population). Talk about cross-species transmission. Consider that even if the same number of people get sick, preventative measures may flatten the curve, reducing strain on emergency services.


Option A (More Dramatic) : Prepare a collection of clear plastic cups. You should have one for each student. In one of the cups, put a sodium hydroxide (NaOH) tablet dissolved in water to create a clear colorless liquid with a high pH. In each of the other cups, fill to the same level with tap water. Put a secret mark on the cup with the sodium hydroxide, or note carefully which student takes the unique cup. You will need a dropper bottle with phenolphthalein pH indicator solution later in the lab. Phenolphthalein is an organic compound (C 20 H 14 O 4 ) used as an acid-base indicator. (Interestingly, it is also the active ingredient in laxatives!) The compound is colorless in acidic solution and pinkish in basic solution (with the transition occuring around pH 9). These preparations must be made before students enter the room.

Warning: Students should be careful not to spill the contents of the cups and to irrigate the affected area immediately with water if they come into contact with the liquid, as it can cause mild irritation to the skin and eyes. Only add a small amount of NaOH to water. Never add water to a large supply of NaOH. The reaction is exothermic (it gives off heat) and could boil a small amount of water rapidly. Although it might seem obvious, DO NOT DRINK any of these fluids!

Option B (Cheap and Easy): If the chemicals are a concern, or are difficult to obtain, you can modify this lab with the use of opaque cups and food coloring, but you'll have to make a few adjustments. The infected person has a cup with water and a lot of dark blue or dark red food coloring, and everyone else has a cup with just plain water. The cups should be opaque rather than clear (so people can't easily see who's infected), and all fluid exchanges should be conducted secretly so that nobody knows whether they are about to encounter an infected person or a healthy one (keep your cup covered with your hand so they can't see if you're infected!). Then proceed as before, with several rounds of fluid exchange, and gather your data at the end on who is infected. Do the fluid exchanges in total silence so as not to give the answer away. Have the uninfected people try to figure out who was the source (because the infected people will know when it happened).

Procedure : Write down the names of all the students in the class who are present. Have students copy this list of names onto the handout of names. The cups with liquid represent bodily fluids, and students will mix their bodily fluids to simulate the spread of a disease. Exchanges will occur in two separate rounds, which we will call "Day 1" and "Day 2". Students will each select a person with whom to exchange fluids. When everyone is done, Day 1 is over and Day 2 begins with a second round of fluid exchange. Therefore, each student will be a "giver" exactly twice, but the number of times each student is a "receiver" will vary. When completed, ask each student (the giver) who their two receivers were, so all students can get the data copied onto their sheets.

Diagnosis & Analysis : Add a drop of indicator solution to each student's cup. If the solution remains clear, they are healthy. If the solution turns pink, they are infected. (Alternately, with Option B, any cup with reddish colored liquid is infected, whereas clear liquid is healthy.) Cross out all of the names of students who came into contact with the disease, and ask them to try to figure out who was the source. Tell them that only one person was initially "infected", and that the best clues will come from looking at people who exchanged fluids with a sick person, but who are not sick themselves. This will indicate that the sick person contracted the disease after that contact, and also shows that this person was not the source of the infection. Insist that students explain the path of infection rather than just guess who was the source. Finally, reveal the source and have students see if they can then trace the path of infection.

15 min. Introduction of the disease simulation and copying of names.

05 min. Fluid exchange Round 1- spreading of the simulated disease.

05 min. Fluid exchange Round 2- spreading of the simulated disease.

05 min. Recording and copying of fluid exchange data to and from the board.

10 min. Determination of the infected individuals while students begin work on lab questions.

05 min. Listen to student theories, and ask for evidence.

05 min. Announcement of the infectious individual, and explanation of the results.

10 min. Continued work on the lab questions, and time for more discussion.

List all of the students in the first column. After two rounds of "bodily fluid exchange" record both contacts and share the data. After the data is recorded, the teacher will add an indicator which tells who lived and who died. You must then try to recontruct the path of this epidemic back to its single source.

How HIV Is Spread

Three conditions must be met for HIV transmission to occur:

1. 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.

2. . 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 body fluids is needed for HIV transmission.

3. . and it must get into the bloodstream.

It is not enough to come into 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 enter only 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.

The next two topics discuss the second and third requirements.

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)
  • Semen
  • Vaginal secretions
  • Breast milk

Blood contains the highest concentration of the virus, followed closely by semen, followed by vaginal fluids. These are the three basic fluids that infect adults with HIV.

The risk from these fluids can be worsened or lessened depending on how they get into someone else's body, which we will discuss below.

Breast milk can 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 minimal 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 probably is not.

Possibly Infectious "Bodily Fluids"

HIV might be transmitted from an infected person to another through:

Pre-seminal fluid is a clear fluid that lubricates men's urethras. It is produced by a different gland than semen. Pre-seminal fluid can contain small amounts of HIV, and so there is a potential risk. However, in practice, the risk is much, much lower than that from blood, semen or vaginal fluid. As in all transmission situations, risk depends on where the fluid is going.

Non-Infectious "Bodily Fluids"

These fluids and substances cannot transmit HIV. Sweat contains no HIV.

The other fluids do not contain enough HIV to infect another person. This is regardless of how they get into the bloodstream. No cases of HIV transmission have ever been documented as a result of these substances. See below for more information.

Ways of Preventing HIV From Entering the Body

  • Protective sex (i.e. wearing a condom when having sex)
  • Not sharing needles
  • Masturbation
  • Abstention from sex

Ways in Which HIV Is Transmitted

Looking at the third condition for transmission (that 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 (See below for detailed information about the actual level of risk for each mode of transmission)
  • Mother to baby (before or during birth, or through breast milk)

Sexual Routes of Transmission

Sexually, the three main ways that HIV is transmitted are:

Vaginal and anal intercourse: For the receptive partner (the "bottom"), the mucous membranes of the anus and vagina are very efficient routes into the bloodstream. HIV may also enter either through routine, minute tearing caused during intercourse (which is often unnoticed).

Anal sex is riskier than vaginal sex, because the membranes are thinner, tearing happens more easily, and there is no natural lubrication. But both are efficient routes for the virus.

It is speculated that for the penetrative partner (the "top"), HIV may infect through the mucous membranes in the meatus (the opening of the urethra). It is believed that uncircumcised men may be at greater risk for HIV for a variety of reasons. For instance, they may not have been told how to correctly use a condom. Because an uncircumcised man has a foreskin and a circumcised man doesn't have a foreskin, each has to put on a condom differently. Uncircumcised men must pull back on their foreskin before rolling on the condom. Neglecting to pull back the foreskin may make condom failure more likely, although no clear evidence supports this idea.

Uncircumcised men having unsafe sex may be at greater risk if HIV infected fluid remains under the penis' foreskin for an extended period of time. The shelter afforded by foreskin may give HIV a more favorable environment in which to survive. The protected area under the foreskin might help shield HIV from air and keep it closer to body temperature.

Oral sex (mouth-penis, mouth-vagina): The risk from oral sex is very minimal as the mouth is an inhospitable environment for HIV, for several reasons. Saliva contains enzymes that break down the virus also, the skin of the mouth is sturdier than in the anus or vagina. There are, however, a few documented cases where it appears that HIV was transmitted orally. These cases are all attributed to ejaculation in the mouth (i.e., exposure to semen, not exposure to vaginal fluid or pre-seminal fluid).

Receiving oral sex is not risky because one is exposed only to saliva.

Non-Sexual Routes of Transmission

Currently, the main non-sexual ways that HIV is transmitted are:

Sharing injection needles: This is an extremely high risk behavior as 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 and ways to reduce the risk of becoming infected with HIV.

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 HIV. 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 HIV is quite difficult to get.

Blood transfusions: Blood donations in the United States have been screened for antibody to HIV type-1 since March 1985 and HIV type-2 since June 1992. This practice has almost eliminated the risk of getting HIV through a blood transfusion. Assuring the safety of the blood supply is a high-tech process requiring at least nine specific tests proper processing, labeling, and storage and vigilant quality control. Routine donations are now tested for HIV and hepatitis C through nucleic acid testing (NAT).

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 in the early years of the epidemic. 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 vaccines 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.

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.

Mother to Child Transmission

The number of children reported with AIDS due to perinatal HIV transmission in the United States peaked at 954 in 1992 and declined 95% to 48 in 2004, largely because of the effectiveness of ensuring that pregnant women are encouraged to be tested for HIV and, for those who are infected, to receive treatments that can significantly reduce the risk of transmitting HIV to a newborn. The CDC reports that perinatal transmission rates can be reduced to less than 2% if women are aware that they are infected with HIV and take appropriate treatments to prevent transmission.

Perinatal HIV transmission continues to occur mostly among women who lack prenatal care or who are not offered voluntary HIV counseling and testing during pregnancy. Many of the perinatal HIV infections each year can be attributed to the lack of timely HIV testing and treatment of pregnant women.

For years, HIV infected women who were pregnant had little choice in how they delivered their baby. C-section delivery was considered the safest option in an effort to prevent HIV transmission to the baby. Today, more and more HIV infected women are delivering vaginally. There are guidelines as to who should and shouldn't have a vaginal delivery. Keep in mind the following are just guidelines and your doctor's choice may vary.

C-section delivery is recommended if:

  • the viral load is unknown or is greater than 1000 copies/ml at 36 weeks of pregnancy
  • there as been no HIV medications taken during the pregnancy
  • there has been no prenatal care prior to 36 weeks of pregnancy
  • a c-section should be scheduled prior to the rupture of membranes ("water breaking")

Vaginal delivery can be done if:

  • there has been prenatal care throughout pregnancy
  • the viral load is less than 1000 copies/ml at 36 weeks of pregnancy
  • HIV medications have been taken during pregnancy

If you are pregnant and have HIV, make sure you are getting the proper prenatal care throughout your pregnancy and talk to your doctor to find out if vaginal delivery is an option for you.

Breast milk can contain HIV, and while small amounts of breast milk do not pose significant threat of infection to adults, it is potentially a viable means of transmission to infants. Mothers infected with HIV should discuss the risk of HIV transmission to their baby via breast milk with their doctor.

Ways in Which HIV Is NOT Transmitted

Insect Bites

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 tract, using the insect as part of its life cycle. HIV does not.

These facts are confirmed by looking 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, they 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, daily 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.

Donating Blood

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 (and time) hadn't killed it already.


Humans are the only animals that can harbor HIV. People sometimes think they can get HIV from pets or other animals, 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.

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 with HIV. This contact has occurred through kissing, sharing food, and many other means. They 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 it an inhospitable site for the virus: acids, enzymes, friction, dilution, air, and more.

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.

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.

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, and 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.

Air does not "kill" HIV, but exposure to air dries the fluid that contains 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% within several hours.

It should be noted that HIV can survive for several days in the small amount of blood that remains in a needle after use, because the blood is trapped where air cannot dry it out. As a result, 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.

Is Someone Who Takes HIV Drugs Able to Transmit HIV?

Some people believe that taking antiretrovirals or having an "undetectable viral load" means that they can't transmit HIV to their sexual partners. That is not true. A person who takes HIV treatments -- even those who have "undetectable" viral load counts -- can still transmit HIV.

Effective drugs, taken properly, can significantly decrease viral load (the amount of virus in one's blood). It is known that the higher one's viral load, the more likely one is to transmit the virus and the lower one's viral load, the less likely one is to transmit the virus. But, regardless, HIV can still be transmitted. It is also important to note that viral load can change from day to day, so one can never be certain of their viral load count at a particular time. In addition, viral load tests only reflect the amount of virus in the blood, not necessarily the level of virus in other bodily fluids, such as semen and vaginal fluid.

Is There a Pill That I Can Take to Prevent Getting HIV?

Since 1996, the federal government has recommended that health care workers that are exposed to HIV through needle stick injuries be provided with antiretroviral medications to help prevent the possibility of HIV infection. For a short period of time after exposure to HIV, virus particles are present only in certain cells of the body. If HIV replication (copying of the virus) can be slowed during that time, the virus may not be able to establish permanent infection in the person's body. The sooner treatment is started, the more likely it is to interrupt HIV transmission. A combination of three antiretroviral drugs must be taken within 72 hours after exposure and must be taken daily for 28 days. This is generally referred to as post-exposure prophylaxis or PEP.

In 2005, the CDC issued guidelines for the use of anti-HIV therapies for individuals exposed to HIV through high risk sexual activities or needle sharing among injection drug users. The guidelines recommend this approach only in very limited circumstances:

  • A high-risk exposure must have taken place between the uninfected person and someone who is known to be HIV-infected.
  • The individuals must seek out treatment within 72 hours (no more than 3 days) after the exposure has occurred.
  • PEP should NOT be seen as a substitute for practices that can help avoid HIV exposure in the first place, such as consistent and correct use of condoms, abstinence from sex or mutual monogamy with an uninfected partner, and the use of sterile syringes when injecting drugs.
  • PEP is NOT recommended for those who have not had an exposure that puts them at high risk for HIV nor is it appropriate for those who have behaviors that result in frequent exposures to HIV.

It is important to note that PEP is not a simple "morning after pill" for those who have had unprotected sex. To be effective, a combination of three antiretroviral drugs must be taken within 72 hours after exposure and must be taken daily for 28 days.

There have recently been reports that taking certain HIV medications prior to engaging in high risk sexual activity may help to prevent you from being infected with HIV. This potential approach to reducing the risk of HIV infection is called pre-exposure prophylaxis or PREP.

Although there is some research currently taking place regarding the potential safety and effectiveness of such an approach, it is not yet known whether there is any protection from these drugs or what the long-term impact of taking such medications is for those who are uninfected. Researchers and medical experts also do not know how long or how frequently one should take this medication for it to be as effective as possible.

Although there are PREP studies occurring in both the United States and in other countries, no drug has been licensed for PREP at this time.

Given the lack of information about this strategy and its effectiveness, individuals should not rely on such an approach to protect themselves from becoming HIV infected.

Can I Get HIV from Tattooing, Piercing, Acupuncture, Electrolysis, or Shaving?

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 have been 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 B and C. 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 the following questions, going back to the conditions necessary for HIV transmission to occur:

  • What is the substance ("body fluid")
  • 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.

Case 1

A man performed oral sex without a condom on another man. His partner ejaculated 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 semen present, which has a high concentration.

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 potential risk because of the semen coming into contact with the mouth. Considering that there are few reported cases of transmitting HIV through oral sex, the risk in this situation is relatively low.

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.

Case 2

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.

Case 3

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.

What Bloodborne Pathogens May You Be At Risk For?

In addition to the previously mentioned diseases, coming into contact with these bodily fluids may put you at risk for much more than you would think, including:

  • Syphilis
  • Malaria
  • Babesiosis
  • Brucellosis
  • Leptospirosis
  • Arboviral infections (especially Colorado tick fever)
  • Relapsing fever
  • Creutzfeldt-Jakob disease
  • Human T-lymphotropic virus type I
  • Viral hemorrhagic fever

I am HIV positive. How can I prevent passing HIV to others?

Take HIV medicines daily. Treatment with HIV medicines (called antiretroviral therapy or ART) helps people with HIV live longer, healthier lives. ART can't cure HIV, but it can reduce the amount of HIV in the body (called the viral load). One of the main goals of ART is to reduce a person's viral load to an undetectable level. An undetectable viral load means that the level of HIV in the blood is too low to be detected by a viral load test. People with HIV who maintain an undetectable viral load have effectively no risk of transmitting HIV to an HIV-negative partner through sex.

Here are some other steps you can take to prevent HIV transmission:

  • Use condoms correctly every time you have sex.
  • Talk to your partner about taking PrEP.
  • If you inject drugs, don't share your needles, syringes, or other drug equipment with your partner.

Watch the video: Dr. Strangelove - Precious Bodily Fluids (August 2022).