HIV transmission: Know the facts
A number of myths have arisen about how HIV can be transmitted. Understanding how the virus does and does not spread can help prevent not only transmission but also misinformation and ungrounded fears.
In September 2017, the Centers for Disease Control and Prevention (CDC) noted that the spread of the HIV virus appears to be slowing, thanks to new and effective preventive measures and treatment.
For example, antiretroviral therapy (ART) means that the amount of virus in the blood can now be reduced to undetectable levels. At these levels, it does not harm the body, and it cannot be passed on to another person.
In addition, the use of pre-exposure prophylaxis (PrEP) offers a high level of protection by stopping the virus from passing through the body, even if exposure occurs. It is a pill that can be taken regularly by those who have a higher risk of exposure.
How can the virus be passed on?
The HIV virus can only be passed on when certain bodily fluids come into contact with each other.
Contact with blood
Health workers should wear gloves to protect themselves from HIV and other pathogens.
HIV is considered a blood-borne virus. This means that the virus must come into contact with the blood to transmit an infection.
However, touching blood where the virus is present will not lead to transmission. This can only happen if blood that contains the virus enters an open wound.
For example, if a person with HIV has an open wound, and fluid from that wound enters an open wound on a person without the virus, HIV can be passed on.
Blood typically contains more of the virus than other bodily fluids, so the highest risk results from exposure to infected blood.
Blood injected directly into the bloodstream is more likely to cause an infection than blood that comes into contact with a small wound.
This can happen in the form of needlestick injuries, sharing needles, and tattoos carried out with unclean or used needles.
Theoretically, HIV can be passed on during a blood transfusion, but screening practices are strictly implemented, making this highly unlikely nowadays.
Contact with other bodily fluids
Some other bodily fluids can transmit the virus.
- pre-seminal fluid
- rectal fluids
- vaginal fluids
- breast milk
However, exposure to infected fluids alone will not cause infection.
The fluid must come into contact with the blood or open mucous membranes of another person for this to happen.
What does not transmit the virus?
HIV cannot be transmitted through the following:
- toilet seats
- swimming pools
- kissing with a closed mouth
- drinking from water fountains
- tears, sweat, or saliva
- physical contact with a person who has HIV
- sharing food and drinks
- consuming foods prepared by a person with the virus
- sharing eating utensils or other personal items
- insect bites, such as mosquitoes
The risks of contracting the virus through other methods of exposure, such as biting, scratching, and thrown bodily fluids, are either extremely small or nonexistent.
HIV may be contracted from used needles such as those shared by intravenous drug users.
Anyone can contract HIV, but a number of factors increase the risk.
- injecting drugs, especially when needles are shared
- getting a tattoo with a used needle.
- engaging in oral, vaginal, or anal sexual intercourse without using a condom
- having an existing sexually transmitted infection (STI)
- frequent exposure to infected fluids, such as in laboratory, medical, or emergency settings
- drug and alcohol use, as these can impair judgment
- exposure to the virus during childbirth, pregnancy, or breastfeeding
Today, the blood supply is considered safe, but sharing needles remains a significant source of transmission.
What about breastfeeding?
Without any form of treatment in place, there is a 15 to 45 percent chance that a mother will pass on the virus to her infant during labor, delivery, or breastfeeding, because of the contact between bodily fluids.
Antiretroviral treatment can reduce this rate to 5 percent.
In some parts of the world, where infection control measures are not strict, an infant may contract HIV from a source that is not their mother. In this case, the infant will have the virus but the mother will not.
A review of studies published in 2015 found that mothers who were breastfeeding infants with HIV had a 40 to 60 percent chance of contracting the virus. Open sores in the mouth can shed the virus into tiny sores on a mother's breast.
The World Health Organization (WHO) recommend that women with HIV combine exclusive breastfeeding with the use of anti-retroviral drugs. Reliably taking anti-retroviral drugs while breastfeeding reduces the risk of transmitting the virus to the infant.
HIV can affect anyone, but some social factors can increase the chances of exposure.
- being susceptible to risk-taking behavior, for example, during the teenage years
- living in an environment where there is limited access to health services
- having reduced negotiating power due to sex, gender, financial, or other status
- fearing to seek medical help due to concerns about stigmatization
All these risks can be reduced through increased awareness of and access to antiretroviral therapy, preventive medication, and support services.
Reducing the risk
Practicing safe sex is one step people can take to reduce the risk of contracting HIV.
A range of effective strategies can now lower the risk of having HIV, even among vulnerable groups.
- using pre-exposure prophylaxis (PrEP) therapy when engaging in high-risk behaviors, which — used correctly — can reduce the risk by up to 92 percent
- never sharing needles with another person
- frequent testing for people with multiple sexual partners
- using gloves and other sterile equipment in medical settings
- using condoms during sex
- using post-exposure prophylactic drugs (PEP) if there is a risk of having been exposed
The United States Preventive Services Task Force updated their guidelines in 2019 to advise that only people with a negative result from a recent HIV screening test are candidates for PrEP. People who have a high risk should take PrEP once every day.
Women with HIV who are pregnant or who plan to become pregnant should discuss risk mitigation strategies with their doctors, including the choice of whether or not to breastfeed.
Undetectable = Untransmittable
Appropriate use of antiretroviral drugs can reduce to zero the risk of spreading the virus to others, and it can halt or delay viral activity within the body.
When the viral load, or amount of virus in the blood, is below 200 copies per milliliter, it is considered undetectable. At this level, it cannot be transmitted to another person.
It is important to follow up on medical care to ensure the viral load remains below the detectable level.
Who should get tested for HIV?
Signs that a person has been exposed to the virus may include intense, flu-like symptoms that occur within a month. Anyone who experiences these symptoms should seek medical help.
The symptoms do not confirm that HIV is present, because other conditions have similar symptoms.
However, if HIV is the cause, early diagnosis will allow for early treatment. This is the most effective way to stop the progression and transmission of the virus. It can protect health and prolong life.
Some people may have the virus but experience no symptoms. Anyone who thinks they may have been exposed to HIV should ask for a test.
Frequent testing is an inexpensive and effective way to stop the spread of HIV.
Testing is recommended:
- when planning to become pregnant, or after becoming pregnant
- before having sex with a new partner
People who have a high risk of contracting the virus, including sex workers, people who use needles that may be shared, and those who regularly come into contact with bodily fluids, should get tested every 3 to 6 months.
Risk assessment tool
The CDC have a risk estimation tool on their website. It works out the risk of HIV transmission for different sexual activities where one person is HIV positive and the other is HIV negative. The tool is based on the most recent evidence.