Does HIV Have Different Strains?

Medically Reviewed on 2/17/2022
HIV AIDS variant
Human immunodeficiency virus (HIV) constantly replicates itself, resulting in multiple strains, which are mainly divided into two types (HIV-1 and HIV-2).

Human immunodeficiency virus (HIV) constantly replicates itself. Some strains multiply faster and are more easily transmitted from person to person than others.

If the doctor knows what strain of HIV a patient has, they will be able to treat the patient more effectively. A blood test can reveal HIV strains. The same test can tell if certain HIV drugs will not work for a patient.

HIV is divided into two types:

  1. HIV-1: Discovered first and is more prevalent worldwide
  2. HIV-2: Less pathogenic and is mostly confined to West Africa

When we talk about HIV, we're usually talking about HIV-1.

Differences between HIV-1 and HIV-2

The primary distinction between HIV-1 and HIV-2 infections is in the mechanism of retroviral pathogenesis, which is still unknown.

  • HIV-1 and HIV-2 share many similarities, including intracellular replication pathways, modes of transmission, and clinical effects that result in acquired immunodeficiency syndrome (AIDS).
  • HIV-2 is less likely to progress to AIDS because of its lower transmissibility.
  • As a result, patients infected with HIV-2 tend to remain non-progressors for a long time, whereas patients infected with HIV-1 progress faster and develop AIDS.
  • Once they progress, the pathological process for both viruses is largely similar, with HIV-2 progressing at higher CD4 counts.
  • HIV-2 infections have lower viral loads than HIV-1 infections.
  • However, in the case of HIV-2 infection, the body's immune response is more protective, slowing the disease progression.
  • Despite this, both need treatment as per the World Health Organization guidelines.

HIV-1 and HIV-2 are further classified into subtypes and groups.

HIV-1 is divided as follows:

  1. Main or M group:
    • The most common is Group M, which is primarily responsible for the global HIV epidemic.
    • A, B, C, D, F, G, H, J, and K are genetically distinct subtypes of Group M. Some of these subtypes combine to form the “circulating recombinant form,” a hybrid virus.
    • Because subtype B is the most common HIV-1 subtype in the Americas, Australasia, and Western Europe, the majority of HIV clinical research is focused on these populations. Although subtype C accounts for nearly half of all HIV patients, little research has been conducted on this subtype.
  2. Outlier or O group and Non-M/O or N group: These are relatively uncommon and are seen in select geographies.

HIV-2 is divided as follows:

  • The two main HIV-2 subtypes that are considered epidemic are A and B, which are usually detected in West Africa and rarely detected in Brazil, Europe, the United States, and India.


A Timeline of the HIV/AIDS Pandemic See Slideshow

How does HIV progress?

Human immunodeficiency virus (HIV) causes the body’s immune system to attack itself and reduces its ability to fight off diseases and infections.

A person may become vulnerable to infections by bacteria, viruses, and disease-causing organisms if their immune system is not healthy and functioning properly. These infections have the potential to cause life-threatening illnesses.

HIV specifically targets CD4 cells, which are a type of white blood cells (T cells) in the immune system. T cells circulate throughout the body, looking for abnormalities and infections in cells. HIV multiplies and destroys CD4 cells after entering the body, severely compromising the human immune system.

HIV-1 infection causes a gradual decrease in CD4+ T cell count and an increase in the viral load (concentration of viral particles in the blood plasma).

The disease progresses in three stages:

  1. Acute or primary stage:
    • This stage occurs shortly after initial infection and is distinguished by rapid viral replication and a decrease in the number of CD4+ cells.
    • Fever, headache, lymph node enlargement, and muscle pain are common early symptoms.
    • Because the symptoms are non-specific, the patient may not associate them with HIV, and they can be easily confused with flu.
    • After one month, the symptoms usually subside, and CD4+ cell levels return to normal.
  2. Chronic or asymptomatic stage:
    • This is an asymptomatic period that lasts 7 to 11 years (varies considerably between individuals).
    • The CD4+ cell count remains normal during this time, but the number of infected CD4+ cells increases.
    • Many patients will be unaware that they are infected and will continue to engage in risky behaviors, increasing the risk of HIV transmission to others.
    • There is an intense immune response during this time, but the immune system eventually becomes overwhelmed and begins to deteriorate, leading to the disease's final stage.
  3. Crisis stage or acquired immunodeficiency syndrome:
    • Patients have a very low CD4+ count at this point, and their immune system is severely compromised.
    • Patients who do not have a functioning immune system are susceptible to opportunistic infections from a wide variety of microbes that can be lethal.

What are the treatment options for HIV?

Currently, there is neither a cure for human immunodeficiency virus (HIV) infection nor a vaccine to prevent it.

Doctors now have an arsenal of drugs at their disposal to control the infection and extend the average life expectancy of HIV-positive patients. The drug regimen required by infected people is known as combination therapy, and it consists of three or more antiretroviral (ARVs) drugs. Moreover, it is referred to as highly active antiretroviral therapy.

There are currently three types of HIV drugs available, all of which have a different mode of action:

  1. Reverse transcriptase inhibitors (RTIs):
    • Stop the virus from replicating by inhibiting reverse transcriptase's role in DNA synthesis
  2. Protease inhibitors (PIs):
    • Prevent viral replication by inhibiting the action of a protease enzyme involved in virus replication
  3. Entry inhibitors (EI):
    • A relatively new drug class that prevents HIV from binding to a coreceptor on the host cell

RTIs and PIs are commonly used in combination therapy. Antibiotics and other drugs are used to treat opportunistic infections associated with the phase three or crisis stage of acquired immunodeficiency syndrome.

What are the side effects of HIV medication?

All ARV drugs cause side effects, but the severity and duration of these effects vary.

Any drug that has been approved for use has undergone extensive research to reduce toxicity, but common side effects include:

Many patients find it extremely difficult to adhere to complex drug regimens, but treatment adherence is critical to reducing the likelihood of drug resistance and keeping the infection under control.

As a result of new treatments, many people living with HIV live long, healthy lives, so never consider HIV as a death penalty. Patients must keep their appointments with their doctor and follow prescribed drugs even if they have side effects.

Medically Reviewed on 2/17/2022
Image Source: iStock Images

Types and Strains of HIV:


HIV Types, Subtypes, and Strains: