HIV Flashcards
SUMMARY
HIV infection causes what?
Which leads to what?
What is the single highest predictor of mortality in HIV?
AIDS
Opportunistic infections and AIDS related cancers
AIDS related conditions
EPIDEMIOLOGY
What is the risk group with the highest proportion of HIV in the UK?
What follows it?
17% of individuals in the UK with HIV are undiagnosed. Who is this, and also late presentation, most likely to occur in?
Is HIV common in people who inject drugs?
MSM
Heterosexual populations from Sub-Saharan Africa
Heterosexual men
Not particularly
TRANSMISSION
Though HIV can be isolated from a wide range of bodily fluids, what are by far the most common?
What is the most significant marker for transmission risk? When is this highest?
Semen, cervical secretions and blood
High HIV viral load - highest in acute infection
SEXUAL TRANSMISSION
What % of infections does this account for?
What % occurs in homosexual men? And heterosexual couples?
What are some factors which increase transmission risk?
It is more commonly passed from who to who?
94%
51% / 45%
Trauma, concurrent STIs, genital ulceration
Men to women, and to the receptive partner in anal sex
PARENTERAL TRANSMISSION
Give some examples of this?
Injection drug use
Infected blood products
Iatrogenic
VERTICAL TRANSMISSION
At what points in pregnancy can this occur? When is the risk highest?
If the viral load is undetectable at delivery, what is the risk of vertical transmission?
What are some interventions to reduce the risk of vertical transmission?
HIV testing should be offered to which children?
In utero, during delivery or at breastfeeding - highest risk at breastfeeding
< 0.1%
Screening for infection in pregnancy, use of ARVs and avoidance of breastfeeding
Children born to HIV+ mothers, or untested mothes from endemic areas
THE HIV VIRUS
The HIV virus is what type of virus?
As a result of this, it is characterised by the possession of which enzyme?
What is the target site for this virus?
Retrovirus
Reverse transcriptase
CD4+ receptors
THE HIV VIRUS
What is the most frequently occurring strain of HIV globally?
HIV-1 is divided into 4 transfers, what are these? Which is the most common?
Which is the most virulent type of HIV?
HIV-2 is found where?
Are the drugs for HIV-1 effective for HIV-2?
HIV-1
M (most common), N, O, P
HIV-1
Almost entirely confined to Western Africa, with a little spread to Europe
Mostly not
CD4
This is a glycoprotein which is found on the surface of a variety of cells. Give some examples?
CD4 is essential for what? Give some examples?
What are the normal parameters?
There is a risk of opportunistic infection when levels fall below what?
T helper lymphocytes (CD4+ cells), dendritic cells, macrophages and microglial cells
Induction of the adaptive immune response: recognition of MHC2 antigen presenting cell, activation of B cells, CD8+ T cells and cytokines
500-1600cells/mm3
< 200cells/mm3
THE HIV VIRUS
Where does this initially infect?
It is then transported to where?
Infection is established when?
Then what happens?
Mucosal CD4+ cells, i.e. Langerhans cells and dendritic cells
Regional lymph nodes
Within 3 days of entry
Disseminated infection
HIV INFECTION AND THE IMMUNE RESPONSE
A key driver of disease progression in HIV is immune activation - what is this?
HIV causes sequestration of cells in lymphoid tissue, what does this lead to?
Reduction in CD8+ T cell activation leads to what?
All of this leads to increased susceptibility to what?
A long term inflammatory state
Reduced circulating CD4+ cells
Dysregulated expression of cytokines, and increased susceptibility to viral infections
Viral, fungal and mycobacterial infections as well as infection induced cancers
TESTING FOR HIV
What are the criteria for groups of people for whom HIV testing is universally offered?
High prevalence areas
Certain clinical settings
High risk groups
In the presence of ‘clinical indicators’
TESTING FOR HIV
What is classed as a high prevalence area for HIV?
Testing should be performed on who?
Any area where local prevalence is > 0.2%
All new patients registering with a GP, and all new hospital admissions
TESTING FOR HIV
What are some clinical areas in which individuals should be tested for HIV as there is a higher prevalence of HIV in individuals accessing these services compared with the background population?
What are some clinical areas in which individuals should be tested for HIV since the risks associated with HIV in these settings are unacceptably high?
People with which conditions should always be tested?
GU medicine, sexual health clinics, TOP services, drug dependency services
Antenatal clinics, assisted conception services
TB, Hep B/C, lymphoma
TESTING FOR HIV
HIV tests are now offered to high risk groups - what are some examples of these?
All patients diagnosed with an STI
MSM
PWID
People from endemic areas
And more…
TESTING FOR HIV
You should always explain to people that they are being offered an HIV test and why. What are some benefits you should tell them about doing this if they were to be positive?
Antibody tests can give results in how long?
How are results given from home sampling approaches with specimens sent to a central lab?
That earlier testing and detection will improve long term health and protect partners
In minutes
Over the phone
TESTING FOR HIV
When testing for HIV serology, what type of blood sample should be taken?
Which markers of HIV are used to detect infection?
Venous
Viral RNA, antigen (p24), antibody (to gp120)
TESTING FOR HIV
What is the recommended UK first line assay?
What is the window period of this test where it may give a false negative?
If one of these tests is negative after what amount of time following exposure, it is highly likely to exclude HIV infection?
4th generation HIV test: tests for HIV antibody and antegen simultaneously
14-28 days
4 weeks
TESTING FOR HIV
What is tested for in a 3rd generation assay?
How sensitive/specific is this test?
What is the window period?
Antibody only (IgG and IgM)
Very
20-25 days
TESTING FOR HIV
Rapid HIV tests (POCT) are also known as what?
These are taken using what samples?
How is the result interpreted?
Home testing
Fingerprick or saliva
By the user
TESTING FOR HIV
Recent infection testing algorithm (RITA) can also be known as what?
This can be used to identify if an infection has occured when?
What sample is used?
How is the sample analysed?
Home sampling
In the preceding 4-6 months
Fingerprick or saliva
It is sent back to the provider and the result is then communicated to the user
HIV INFECTION
Without treatment, the average time to death after HIV infection is what?
In Europe, the diagnosis of AIDS remains based on what?
9-11 years
The diagnosis of specific clinical conditions (no inclusion of CD4 count)
PRIMARY HIV
This refers to what time period?
What happens in this time period?
What proportion of people present with symptoms?
What is significant about the first 2-4 weeks?
The first 6 months following HIV acquisition
Uncontrolled viral replication, high levels in the plasma, and high infectiousness
80%
Can be silent, both clinically and serologically