Infectious diseases Flashcards
What does HIV stand for
Human immunodeficiency virus
What does AIDS stand for
Acquired immunodeficiency syndrome
What type of virus is HIV?
RNA retrovirus
Pathology of HIV
HIV enters & destroys the CD4 T helper cells
Initial seroconversion flu like illness occurs within a few weeks of infection
infection then becomes asymptomatic until it progresses & patient becomes immunocompromised
How is HIV transmitted?
- Unprotected anal, vaginal or oral sexual activity.
- Mother to child at any stage of pregnancy, birth or breastfeeding. This is referred to as vertical transmission.
- Mucous membrane, blood or open wound exposure to infected blood or bodily fluids such as through sharing needles, needle-stick injuries or blood splashed in an eye.
Name some AIDS defining illnesses
Kaposi’s sarcoma Pneumocystis jirovecii pneumonia (PCP) Cytomegalovirus infection Candidiasis (oesophageal or bronchial) Lymphomas Tuberculosis
Why do AIDS defining illnesses occur in late stage HIV?
The CD4 count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear
How is HIV screened for?
Everyone admitted to hospital with infectious disease regardless of risk factors
Anyone with risk factors
only need verbal consent before testing
When are antibody tests positive for HIV?
may not be present in early infection, but most people develop antibodies to HIV at 4-6 weeks but 99% do by 3 months
How is HIV tested for?
- Antibody testing - ELISA test and confirmatory Western Blot Assay
- p24 antigen - appears early in the blood as viral RNA rises, positive from 1 week to 3/4 weeks after infection
- Combination tests - p24 antigen + HIV antibody. If it’s positive, repeat to confirm.
- Can do PCR testing for HIV RNA levels - directly quantifies the amount of HIV in the blood and gives a viral load
When should someone asymptotic be tested for HIV after exposure?
4 weeks after possible exposure, then repeat at 12 weeks if there’s a negative result
What are the symptoms of HIV seroconversion illness?
sore throat lymphadenopathy malaise, myalgia, arthralgia diarrhoea maculopapular rash mouth ulcers rarely meningoencephalitis
when do people have HIV seroconversion illness after exposure to the virus?
3-12 weeks after infection
in what % of people is initial HIV seroconversion symptomatic?
60-80%
increased symptomatic severity is associated with poorer long term diagnosis
How is HIV monitored?
1) CD4 count - CD4 cells are destroyed by the virus, lower the count the higher the risk of opportunistic infection.
500-1200 cells/mm3 normal
<200 cells/mm3 = AIDS & high risk of opportunistic infections
2) Viral load - number of copies of HIV RNA per ml of blood. Undetectable = viral load below the labs recordable range.
Tx for HIV and what’s the goal of it?
Antiretroviral therapy (ART) with the aim of achieving a normal CD4 count and undetectable viral load.
Highly active anti-retrovirus therapy (HAART) medication classes:
- Protease inhibitors (PIs)
- Integrase inhibitors (IIs)
- Nucleoside reverse transcriptase inhibitors (NRTIs)
- Non-nucleoside revisers transcriptase inhibitors (NNRTIs)
- Entry inhibitors (Els)
Usually start with 2 NRTIs (tenofovir & emtricitabine) + a 3rd agent
What additional management if needed for people with HIV?
prophylactic co-trimoxazole - for CD4 count <200 to protect against pneumocystis jirovecii pneumonia (PCP)
Monitor CVD risks & give statins
Yearly cervical smears - HIV predisposes to HPV
Keep up with vaccinations but avoid live vaccines
Advise condons and dams (unlikely to pass on virus if undetectable viral load)
C-section unless undetectable viral load
No breastfeeding unless undetectable viral load
Mx of children born to HIV positive mothers
ART for 4 weeks to reduce risk of vertical transmission
What is post exposure prophylaxis for HIV?
used after exposure to HIV to reduce the risk of transmission
not 100% effective
Needs to be started within 72 hours, sooner its started the better
Do HIV test initially & at 3 months to confirm negative status
Protected sex until confirmed negative at 3 months
What is given as post exposure prophylaxis for HIV?
Truvada (emtricitabine + tenofovir) & raltegravir for 28 days
Name some neurocomplications of HIV
Toxoplasmosis Primary CNS lymphoma TB Encephalitis Cryptococcus Progressive multifocal leukoencephalopathy AIDS dementia complex
What is toxoplasmosis?
A disease caused by the toxoplasma gondii parasite that can be picked up from raw meat, water or unwashed fruit/veg. Cats carry the parasite.
It accounts for 50% of cerebral lesions in patients with HIV
Symptoms and Ix for toxoplasmosis
Constitutional symptoms
HEadache
Confusion
Drowsiness
CT - single/multiple ring enhancing lesions, mass effect may be seen
Mx of toxoplasmosis
sulfadiazine and pyrimethamine
