What causes one partner to be hiv positive and the other negative

Overview

The scenario where one partner in a relationship is HIV-positive and the other is HIV-negative, often referred to as a serodiscordant couple, is a common and manageable situation. Understanding the modes of HIV transmission is crucial to comprehending why this discordance occurs and how it is maintained. HIV (Human Immunodeficiency Virus) is a virus that attacks the body's immune system. It is not transmitted through casual contact like hugging, kissing, sharing utensils, or toilet seats. Transmission requires the virus to enter the bloodstream of an uninfected person from the bodily fluids of an infected person.

How HIV is Transmitted

The primary routes of HIV transmission are specific and well-defined:

• Sexual Contact: This is the most common mode of transmission. HIV can be transmitted during vaginal, anal, or oral sex if protective measures are not used. The virus is present in semen, pre-seminal fluid, rectal fluids, and vaginal fluids. Anal sex carries a higher risk of transmission than vaginal sex due to the delicate lining of the rectum.
• Sharing Needles and Syringes: Intravenous drug use, where needles and syringes are shared, is another significant route of HIV transmission. This also applies to sharing other injecting equipment like cookers and cotton.
• Mother-to-Child Transmission: An HIV-positive mother can transmit the virus to her child during pregnancy, labor and delivery, or through breastfeeding. However, with proper medical care and treatment, the risk can be reduced to less than 1%.
• Blood Transfusions and Organ Transplants: While rare in countries with rigorous screening procedures, HIV can be transmitted through contaminated blood transfusions or organ transplants. This risk is very low in developed nations due to routine testing of donated blood and organs.

Why One Partner Remains HIV-Negative

In a serodiscordant couple, the HIV-negative partner remains uninfected primarily because the virus has not entered their bloodstream. This can be due to several factors, often working in combination:

• Consistent and Correct Condom Use: Latex or polyurethane condoms act as a barrier, preventing the exchange of bodily fluids during sex. When used correctly and consistently for every sexual act, condoms are highly effective in preventing HIV transmission.
• Undetectable Viral Load (U=U): For an HIV-positive partner undergoing effective Antiretroviral Therapy (ART), the amount of HIV in their blood can become so low that it is undetectable by standard laboratory tests. When the viral load is consistently undetectable, it is impossible to transmit HIV sexually. This is known as "Undetectable = Untransmittable" (U=U). This is a cornerstone of modern HIV management and allows serodiscordant couples to have sex without condoms and without the risk of transmission.
• Pre-Exposure Prophylaxis (PrEP): PrEP is a daily medication taken by HIV-negative individuals at high risk of acquiring HIV. When taken consistently, PrEP can significantly reduce the risk of infection. It is often recommended for individuals in serodiscordant relationships as an additional layer of protection.
• Post-Exposure Prophylaxis (PEP): PEP is a course of HIV medication taken within 72 hours after a potential exposure to HIV. It is used in emergency situations, such as condom breakage or sexual assault, and can help prevent infection.
• Lack of Exposure to Infected Bodily Fluids: If the HIV-positive partner has a very low viral load (even if not undetectable) and precautions are taken, or if the specific high-risk fluids (semen, vaginal fluids) are not exchanged, the risk is lower. However, relying solely on this without other measures is not recommended.
• Circumcision: While male circumcision does not prevent HIV transmission, studies have shown it can reduce the risk of female-to-male HIV transmission by about 60%. However, it is not a standalone prevention method.

Living in a Serodiscordant Relationship

Serodiscordant relationships are increasingly common and can be healthy and fulfilling. Open communication between partners is vital. The HIV-positive partner should be on ART and have their viral load monitored regularly to maintain an undetectable status. The HIV-negative partner may consider PrEP, especially if condoms are not consistently used. Regular HIV testing for the HIV-negative partner is also advisable to ensure their status remains negative.

The success of maintaining a serodiscordant relationship relies on a combination of medical advancements and consistent adherence to prevention strategies. With proper management, the risk of HIV transmission from a positive partner to a negative partner can be reduced to near zero, allowing couples to focus on their relationship without the overwhelming fear of transmission.