UBC Objectives: HIV Primary Care

By the end of postgraduate training, using a patient-centred approach and appropriate selectivity, a resident, considering the patient’s cultural and gender contexts, will be able to...

• Describe HIV transmission routes, risk factors and counsel prevention strategies
• Explain HIV/AIDS pathogenesis

Some background information about HIV (thanks sexandu.ca for yet again being a great reference, along with the CDC webpage on HIV/AIDS).

HIV transmission routes

1. Blood
2. Genital fluid
3. Breast milk

If there is any mixing of any of these fluids between a person who has HIV with a recipient mucous membrane (rectum, vagina, penis, mouth), damaged tissue, or bloodstream (ex via a needle/syringe), transmission can occur.

HIV risk factors
Per Sexandu.ca, the following are risk factors for acquiring HIV:

1. Having unprotected oral, vaginal or anal sex with someone who has HIV
2. Sharing needles or other drug paraphernalia
3. Having had previous STIs
4. Having had an organ transplantation or blood transfusion prior to 1985
5. Getting tattooed with non-sterile needles
6. Having had multiple sexual partners
7. Increased risk of transmission during pregnancy, childbirth or breastfeeding (mother to child)
8. Having unprotected sex with someone from a country where HIV is common

Basically, risk of acquiring HIV is mediated by sexual activity, needles (IVDU, tattoos), and pregnancy.

HIV prevention strategies
There are ways to prevent coming into contact with the virus and ways of reducing the chance of hating the infection in case there is contact with the virus:

1. Use condoms during sexual activity (oral, vaginal, anal)
2. Avoid sharing contaminated needles
3. For someone who knows they will be having intercourse or will otherwise be exposed to bodily fluids of someone with HIV, they can consider pre-exposure prophylaxis (PrEP) to prevent transmission of HIV. This is not without risks and requires consultation with a doctor.
4. For someone with a likely exposure to HIV through contact with blood, breast milk, vaginal or anal secretions, post-exposure prophylaxis (PEP) can reduce the risk of becoming infected with HIV. PEP needs to be started within 72 hours of exposure for maximum effect.
5. Reduce the number of sexual partners

HIV Pathogenesis
In the absolute simplest way possible that I can describe what is going (how I would describe to patients to explain what is going on, probably with lots of inaccuracies because it's far too simple to paint a proper picture of this highly complex disease):

1. HIV transmission occurs (see above)
2. The virus binds and fuses with a type of white blood cell (CD4 cell). It inserts its DNA into the CD4 cell's DNA, such that now as the white blood cell  reproduces, the virus also replicates its DNA (this is what makes it a retrovirus). Levels of the viral DNA in the body increase exponentially, and as it does, it kills off the host CD4 cells. This peaks about 2-4 weeks after acquiring the infection and commonly manifests with flu-like symptoms (fever, headache, rash). 
3. Then the patient may start to feel a bit better because other white blood cells of the immune system (CD8 cells) with ability to kill off cells that contain HIV have begun multiplying. This leads to a dip from the previous rise in viral DNA in the body, though CD8 cells are unable to entirely clear the body of all infected cells (the viral DNA lies "dormant" in many CD4 cells, not expressing any signs that the CD4 cell is infected with it so that it can be targeted by the CD8 cell).
4. Because there is great destruction of CD4 cells, cells that are very important mediators in providing the defence to fight off infection, the HIV-infected person may now feel better for a while, but they become extremely susceptible to acquiring infections, including many that would normally be mild or not even take hold in the body altogether (aka opportunistic infections). They are at much greater increased risk of disease and death.
5. Antiretroviral therapies help to prevent the virus from reproducing, but they are not able to clear the body of the virus altogether (dormant in CD4 cells). If known to be HIV(+), a clinician can monitor the patient's CD4 cell counts to stratify the patient's risk of acquiring infection, and offer strategies to mitigate their risk of acquiring infections accordingly.