HIV Flashcards
first identified in the
early 1980s
why if the incidence (new cases) of HIV is decreasing is the, prevalence (total cases) of HIV is increasing
as life expectancy with disease increases.
HIV specifically affects
CD4 cells (via CD4 receptors) - replicates and destroys cells
extent of HIV is estimated by
patients CD4 T cell count
stage 1
corresponds to a ‘normal’ CD4 count >500 cells/μL and the patient is usually asymptomatic;
Stage II
is when the count <500 cells/μL and the patient starts to show mild symptoms;
Stage III
is described as a CD4 count <350 cells/μL and symptoms start to become more advanced;
Stage IV
is when the CD4 count <200 cells/μL and the presentation is more severe, also defined as AIDS.
clinical stages
seroconversion
latent stage
AIDs
serconversion
this stage is characterised by acute HIV syndrome with symptoms: - fever - malaise - weight loss - generalised rash. This is seen on the image below where the CD4+ count initially drops on initial infection and copies of the HIV virus spike in number.
Latent stage
- CD4+ numbers slowly drop, and viral load slowly increases but the disease is clinically silent. HIV associated infections may begin to develop in the late stages.
AIDS
- when CD4+ count drops below 200 cells/μL and opportunistic infections begin to take hold.
AIDS is the
o Most advanced stage of HIV infection where patient has become immunodeficient
AIDS patients are susceptible to
opportunistic infections: Pneumocystis pneumonioa Candidiasis Protozal infections
Patient risk factors
- Anyone
- IV drug abusers
- Unprotected sex
- Having another STI
HIV pathogen is a
retrovirus
(ssRNA –> DNA –> ssRNA)
- Infects cells with CD4 surface receptors (T helper lymphocytes)
- HIV replicates inside cells
Life cycle of HIV
- Free virus
- Binding and fusion- virus binds to a CD4 molecule and one of two coreceptors (either CCR5 or CXCR4). Virus fuses with cell
- Infections- virus penetrates cells and empties content into cell
- Reverse transcription- ss strands of viral RNA are converted into dsDNA by reverse transcriptase enzyme
- Integration- viral DNA is combined with the cells own DNA by the integrase enzyme
- Transcription- when the infected cells divide, the viral DNA is read and long chain of proteins are made
- Assembly- sets of viral protein chains come together
- Budding- immature virus pushes out of the cell, taking some membrane with it
- Immature virus breaks free of the infected cell
- Maturation- protein chains in the new viral particles are cut by the protease enzymes in to individuals proteins that combe to make a working virus
patient symptoms
- Flu-like symptoms
- Oral candidiasis
- Liver and spleen enlargement
- Nausea and vomiting
- Rash
Acute HIV infection main symptoms
- central malais
- systmeic fever
- weight loss
- pharyngitis
- mouth sores
- thrush
- myalgia
- rash
- liver and spleen enlargment
- nausea and vomiting
main symptoms of AIDS
- Encephalitis
- meningitis
- retinitis
- pneumocystisi pneumonia
- TB
- Tumors
- esophagitis
- chronic diarrhea
mode of tranmission
Sexual contact is one mode of transmission - but not the only one.
Any contact of infected bodily fluids with mucosal tissue, blood or broken skin can be a route of transmission. Therefore, apart from sexual contact (that accounts for 95% of infections), HIV can also be transmitted through medical procedures such as blood transfusions, contaminated needles (mainly through needle exchange among IV drug users), or perinatal transmission(vertical transmission).
treatment is
not curative but will increase life expectancy
The earlier HIV is diagnosed, the better
the prognosis as the higher the CD4+ count can be maintained
types of tests
rapid test
serology
PCR
Rapid test (Point of care test)
Low cost
Rapid that can be done at hone as a discreet postal test
Involves either blood testing through a finger prick or saliva
Very few false negatives
Does produce false positives- need to be confirmed with serology testing
Serology
- Involves a full blood sample sent off to a lab with much slower results (7-10 days)
- Looks for HIV antigen and HIV antibody
- More accurate but might result in a false negative result
PCR
Detects HIV nucleic acid
Highly sensitive test which can detect very early infection
Expensive
Results can take up to a week
Not used for initial HIV testing but for follow-up and monitoring treatment response
Who should be tested?
- Everyone in a population with an incidence rate > 2/1000
- Bacterial pneumonia/TB [Resp]
- Meningitis/dementia [Neuro]
- Severe psoriasis; recurrent/multidermal shingles [Derm]
- Chronic diarrhoea/weight loss with unknown cause [Gastro]
- Any unexplained blood abnormality [Haem]
- Lymphoma, anal cancer [Onc]
- Cervical intraepithelial neoplasia (CIN) [Gynae]
- Any STI/HepB/HepC
treatment for HIV
a combined therapy
Patients are prescribe a combination of 3 anti-retrovirals (ARVs) (triple blood therapy)
PEP stands for
post-exposure prophylaxis
post-exposure prophylaxis
Early initiation of ARVs reduces dissemination and replication of HIV in tissue and bodily fluids
- Evidence limited (animal studies/ observational)
- Assess risk
- Give x 3 ARVs for 28 days
- Start ASAP (max up to 72 hours)
- HIV test at baseline, 1 month and 3 months
Ethical dilemmas
- Testing should be done with consent from the patient who should be then trusted to disclose their status with their partner (s)
- However, in some situations we might asked not to tell a patients partner
- Ethical dilemma rests on patient confidentiality vs harm to the general public
- Advised to make sure to talk to the patient through the importance of the disclosure of such info
Outcome of infection
- No cure
- Chronic infection +/- disability
- Death- AIDS
- If diagnosed late and untreated
- Other infection will kill you
