HIV, or Human Immunodeficiency Virus, is one of many RNA viruses, which usually infiltrate cells and command them to produce certain proteins. However, HIV is a retrovirus, a category of RNA viruses containing the enzyme reverse transcriptase, which can make DNA from RNA.This allows the virus to insert its genetic information into the host’s genome. To do this, HIV virions will bind to CD4/Helper T cells, important immune cells that activate B cells and white blood cells, along with producing cytokines. Once they integrate their DNA into the CD4 cells, they force them to produce thousands of viral clones. This not only increases the amount of HIV in the body, but also destroys the CD4 cell in the process, diminishing the host’s immune response. It is estimated that HIV can use this method to manufacture 10 billion particles in a single day (Perelson et al.)

Upon initial infection, a strong immune response will occur, but as the disease progresses, most of the virus is detected and attacked. This early stage is often mistaken for a cold, as symptoms are mild, and eventually most of the virions are wiped out. However, some linger, and they continue to chip away at the host’s CD4 cells. This makes patients extremely vulnerable to opportunistic infections, as their immune systems are compromised. This is why HIV and tuberculosis are such a deadly combination: while most cases of TB are latent, the weakened immune system of HIV patients allows the active form of the disease to progress. Those infected with HIV have “up to 20 times higher risk of developing active TB” than those without it, according to the WHO.

Acquired Immunodeficiency Syndrome, or AIDS, is characterized by the development of such an opportunistic infection, or one of over twenty types of cancer that may arise as a result of individuals’ destroyed immune systems. It is estimated that about 50% of untreated HIV patients will develop AIDS, and diagnosis typically takes 10-15 years from initial HIV infection. 

HIV is transmitted via bodily fluids such as blood, semen, and vaginal secretions, but not airborne particles or respiratory droplets. HIV is more likely to be spread via anal than vaginal sex, which is why homosexual men are disproportionately affected by this disease (Wilton). Many HIV treatments exist today, though none can entirely cure the disease. However, people living with HIV taking antiretroviral therapy (ART) can suppress viral levels to an “undetectable” degree, at which point they will not transmit HIV to others (Cleveland Clinic).

I’ve noticed through this series that there are so many diseases that you hear about, and maybe know a little about, but don’t fully understand. I didn’t know that AIDS wasn’t really its own disease, but more of a progression of HIV mixed with some sort of other development (cancer, TB, etc.). I appreciate this series because I get the full picture of a disease that has played such a huge role in human history, even though pathology/epidemiology is not my area of study.

As always, my Education in Epidemiology posts are based on episodes from This Podcast Will Kill You. However, I did a fair bit of extra research to write this week’s post, as I found myself wondering about additional information that wasn’t directly addressed in the podcast. Some references were directly cited in the text, while others were used as general background to ensure that everything I said was correct/to provide additional context. They are listed separately below.

My club is in its Microbiology unit, so some of our members gave presentations on pathogens that interested them. I took the opportunity to write about the next disease on my list, but making the slideshow and delivering the presentation really helped me understand HIV a bit better. Now, writing about it in more detail, I understand it better than ever. Almost like I have this website for a reason!

Of course, this is just part one, the biology. Next week will feature the history of the disease, so stay tuned to learn with me!

Direct citations (in order of appearance):

Perelson, A. S., et al. “HIV-1 Dynamics in Vivo: Virion Clearance Rate, Infected Cell Life-Span, and Viral Generation Time.” Science, vol. 271, no. 5255, Mar. 1996, pp. 1582–86, https://doi.org/10.1126/science.271.5255.1582.

World Health Organization. “HIV and Tuberculosis.” Www.who.int, www.who.int/westernpacific/health-topics/hiv-aids/hiv-and-tuberculosis.

Wilton, James. “Risk of Exposure to HIV/AIDS.” Stanfordhealthcare.org, 2024, stanfordhealthcare.org/medical-conditions/sexual-and-reproductive-health/hiv-aids/causes/risk-of-exposure.html.

Cleveland Clinic. “What Is Antiretroviral Therapy?” Cleveland Clinic, 18 Sept. 2023, my.clevelandclinic.org/health/treatments/antiretroviral-therapy.

General information: https://thispodcastwillkillyou.com/2018/02/10/episode-12-hiv-aids-apathy-will-kill-you/ 

Additional information on the HIV life cycle: https://www.thewellproject.org/hiv-information/hiv-drugs-and-hiv-lifecycle 

AIDS definition: https://www.who.int/news-room/questions-and-answers/item/hiv-aids