The fight against AIDS: How can HIV be transmitted through semen?

By (embryologist), (embryologist) and (biochemist).
Last Update: 09/16/2022

December 1 marks World AIDS Day. AIDS is a disease that affects thousands of people around the world and for which there is currently no definitive cure, although there is treatment to alleviate the symptoms.

AIDS is caused by HIV (human immunodeficiency virus), which destroys the cells of the immune system and weakens the entire human organism .

In this article we will explain the different ways in which the virus is transmitted, but we will focus on detailing how AIDS is transmitted through semen.

Differences between HIV and AIDS

It is very common to confuse the terms HIV and AIDS, but in reality they are not the same. To follow, we will describe what each of these concepts is:

human immunodeficiency virus. This is the virus that causes the disease. HIV is a retrovirus that affects the immune system of infected persons by destroying the lymphocytes (white blood cells) responsible for the production of antibodies.
acquired immunodeficiency syndrome. This term is used to describe the last stage of HIV infection, where the immune system has been gretly weakened and severe symptoms appear. At this point the so-called opportunistic diseases, infections or neoplasms appear. These threaten the life of the infected person because their body is not able to defend itself.

It is very important to note that not all HIV-positive (HIV-infected) people eventually develop AIDS. Today, antiretroviral treatments allow HIV positive people to keep their viral load under control and lead a normal life.

How does HIV infection work?

The HIV virus first invades a host cell. Once there it cannot replicate by itself. To replicate itself and create more copies of the virus, it needs to use the internal replication machinery of some cells.

Generally, HIV targets T4 lymphocytes of the immune system, although it also invades other cell types such as macrophages and dendritic cells.

T4 or CD4 lymphocytes are the cells of the immune system responsible for fighting infectious agents by making antibodies.

The binding between the virus and the lymphocyte takes place through the CD4 receptors that these cells possess.

HIV then inserts its genetic material into the cell interior, which is integrated into the lymphocyte's DNA and can then multiply.

Viral load refers to the number of copies of the virus in the blood of those affected. The higher the viral load, the lower the population of healthy lymphocytes and the weaker the immune system.

Routes of HIV transmission

HIV is one of the most feared sexually transmitted diseases (STD). This is due to the serious effects it causes and the fact that there is no definitive cure. The main routes of HIV infection are as follows:

  • Blood
  • Fluids such as semen and vaginal secretions
  • Pregnancy and breastfeeding

As such, HIV can be transmitted through sexual intercourse, open wounds, exchange of syringes or any other sharp material.

It should be noted that the concentration of viral load in blood is much higher than in seminal and vaginal fluid. A small amount of blood can cause transmission, while the risk of transmission would be lower for the same amount of sexual fluids.

In any case, sexual practices without a condom with a person with HIV are risky. During intimate relations it is easy for small wounds to occur that may favor blood transmission of the virus.

To follow, we are going to explain these routes of transmission in more detail.

By blood

As we have said, blood is the fluid with the highest HIV infectivity capacity. Therefore, any contact of wounds or mucous membranes with the blood of a person with HIV will have a high risk of contagion. Some examples are:

  • Sharing syringes, needles or other injection material.
  • Sharing any sharp instruments that have been in contact with infected blood, such as razors.
  • Communal use of non-sterile sharp and cutting instruments for skin piercing, such as those used in tattooing, piercings, acupuncture, ear piercing, etc.

It should be noted that, with the right temperature conditions, HIV could live in a used needle for up to 42 days.

Blood transfusions are no longer considered a means of contagion, thanks to the strict controls carried out on donated blood.

Unprotected sex

Both vaginal and anal sex are the most common ways in which HIV is transmitted. For this reason, it is recommended that both heterosexual and homosexual relations be protected, i.e., with barrier protection methods such as condoms.

On the other hand, although saliva is not a means of transmission, oral sex is not totally excluded from the probability of transmission. Although it is true that the risk is lower, there may be small wounds in the mouth that allow transmission through the bloodstream.

Semen is the best known means of sexualtransmission of HIV. Specifically, semen is composed of spermatozoa and seminal fluid. Virus particles are suspended in this seminal fluid or may even adhere to the spermatozoa.

Finally, it is important to note that HIV infection can occur both from male to female and female to male. It can also occur between people of the same sex.

Vertical transmission

Vertical transmission of HIV refers to the transmission of the virus from mother to baby during pregnancy, childbirth or breastfeeding.

Mothers with a high viral load have an increased risk of transmitting HIV to their child during gestation due to shared blood circulation through the placenta and umbilical cord.

There is also a risk of transmission during breastfeeding, as HIV can be found in breast milk. Therefore, it will be necessary to resort to formlula feeding in cases of HIV-positive mothers.

How HIV is NOT transmitted

Unlike other types of viruses, HIV is not transmitted through the air or water.This is because it is not able to survive outside the human body.

The following situations are not routes of HIV infection:

  • Contact with saliva, tears, sweat, feces or urine. Therefore, there is no problem in touching or kissing a person with HIV.
  • Sharing dishes, food or beverages.
  • Sharing shower, toilet or towels.
  • Mosquito bites. Neither animals nor insects carry HIV.

Generally, there is no risk in living with a person with HIV. In addition, breakthroughs in antiretroviral treatment have enabled seropostive people to reduce their viral load to undetectable levels (<50 copies/ml).

FAQs from users

What are the chances of catching HIV using a condom?

By Andrea Rodrigo B.Sc., M.Sc. (embryologist).

If sexual relations with an HIV-positive person are maintained with a condom, the probability of contagion is very low, since the condom will prevent contact between sexual fluids and also contact with blood that may be released both vaginally and through any wound that may have occurred.

Can HIV be transmitted by rubbing genitals?

By Andrea Rodrigo B.Sc., M.Sc. (embryologist).

Although the probability is low, if the rubbing of genitals is direct, i.e., without underwear, contagion is possible, provided that there has been contact of sexual or blood fluids even though there has been no penetration.

Is there a risk of HIV transmission by accidental puncture wounds?

By Andrea Rodrigo B.Sc., M.Sc. (embryologist).

As mentioned in the article, one of the strongest routes of infection is via blood, since the concentration of virus in the blood of an infected person is high. For this reason, an accidental or voluntary puncture with a syringe or any sharp material can be a reason for contagion.

Is there a probability of HIV infection due to condom breakage?

By Andrea Rodrigo B.Sc., M.Sc. (embryologist).

If the condom has broken and there has been contact with the seminal fluid of a male carrier, the woman has a high risk of being infected.

Can HIV particles be present in pre-ejaculatory fluid?

By Andrea Rodrigo B.Sc., M.Sc. (embryologist).

Yes, viral particles are mainly found in the plasma of the seme, which the pre-ejaculatory fluids are made from. Hence the pre-ejaculatory fluids can be a means of HIV transmission.

If you are interested in learning more about the relationship between HIV and pregnancy, you can continue reading here: Can you have a healthy pregnancy if you are HIV positive?

Fore more information about reproduction options where the male is HIV positive you can access this article: Sperm washing for assisted reproduction in HIV positive patients.

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Authors and contributors

 Andrea Rodrigo
Andrea Rodrigo
B.Sc., M.Sc.
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics. More information about Andrea Rodrigo
 Zaira Salvador
Zaira Salvador
B.Sc., M.Sc.
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Michelle Lorraine Embleton
Michelle Lorraine Embleton
B.Sc. Ph.D.
PhD in Biochemistry, University of Bristol, UK, specialising in DNA : protein intereactions. BSc honours degree in Molecular Biology, Univerisity of Bristol. Translation and editing of scientific and medical literature.
More information about Michelle Lorraine Embleton

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