HIV and AIDS: Pathology review

Two people come to the infectious disease clinic. The first one’s David, a 42 year old man who has a fever, associated with a cough and difficulty breathing. David mentions that he’s HIV-positive, so you decide to run a blood test, which reveals an alarming T cell count of 180 cells / mm3. You immediately ask for a chest X-ray, which shows gray hazy-looking areas in both lungs. Next comes Charles, a 32 year old man. Charles was referred to the clinic by his dentist, who detected white plaques on both sides of his tongue. When you try to scrape the plaques with a tongue depressor, you realize that they can’t be removed. Upon further questioning, Charles tells you that lately he’s been losing a ton of weight, although he hasn’t been exercising or dieting at all. You decide to ask for an HIV-1/2 antigen/antibody immunoassay, which turns out positive. Okay, now both David and Charles have HIV, which stands for human immunodeficiency virus. HIV specifically targets the cells of our immune system, leading to progressive immunodeficiency, which is when the immune system begins to fail gradually. Ultimately, affected individuals can develop AIDS, or acquired immunodeficiency syndrome. What’s important to note is that AIDS puts at increased risk of certain opportunistic infections or tumors that a healthy immune system would usually be able to fend off.

Now, HIV can be transmitted via certain bodily fluids from an infected person, including blood, genital fluids like semen or vaginal discharge, and breast milk. However, HIV is not present in saliva, sweat, urine, or feces. Now, to contract the infection, these bodily fluids need to come into direct contact with a healthy person's blood, broken skin, or mucosal surfaces.

The most common means of transmission is horizontal via sexual intercourse, especially via male-to-male transmission, but also male-to-female and female-to-male transmissions can occur, while female-to-female transmission of HIV is quite rare. The next most common means of horizontal transmission involves direct blood-to-blood contact, which, remember, is most common among intravenous drug abusers who share needles. Less commonly, blood-to-blood contact can occur via accidental needlestick injuries, or by transfusing blood products from an infected donor. To prevent this, blood donations are always screened for infections like HIV, among others. Finally, for your exams, you must absolutely know that HIV can also be passed via vertical transmission, which means that a pregnant individual can transmit the infection to their child before birth via the placenta, as well as during delivery via blood or genital fluids, and afterwards via breast milk. And that’s very high yield!