Ok @Mukiri, you bring up a different angle to his query that I hadn't foreseen.

In the HIV life cycle, it ordinarily takes about 3weeks to 6 months for the virus to appear in blood after initial sexual exposure. This period can vary, either shorter or longer, depending on your initial immune system prior to exposure. This is what is generally known as the window period of the infection, i.e. the period during which one is HIV +ve and infectious (i.e. capable of infecting others) but the virus isn't yet detectable in blood. That's why it's generally recommended to repeat the test 30days and 90days (3 months) after the initial test. The vast majority of people, well over 90%, have a measurable/detectable immune response within 3 months.

I know at the back of your mind is probably a curiosity about the mechanisms of testing, a curiosity I now seek to assuage. There generally are two types of HIV tests that we use locally:

i. Antibody-based tests e.g. Western blot and ELISA (Enzyme-Linked ImmunoSorbent Assay) test. These generally test for the anti-HIV antibodies. This means that after the initial exposure, the virus must replicate enough for the body to mount an immune response whose antibodies are then detected by the test. This explains the latent or lag-period during which it is possible to get a -ve test even though one is actually +ve.

Being an antibody-based test, two main candidates are especially likely to give false +ve (as opposed to the aforementioned false -ve) results:
- candidates of a HIV vaccine test.
-young babies born of HIV +ve mothers, since babies get and rely on maternal antibodies until such a time that their immune systems are mature enough to make their own (see a brief explanation here: http://biology.stackexch...ze-their-own-antibodies).

The rapid tests commonly used in hospitals and VCT Centres fall under this category.

ii. Antigen-based tests e.g. PCR and p24 tests. These tests detect the actual viral DNA (the antigen) in blood long before the body has had a chance to mount an immune response to it. For this reason then, it is the most accurate but also very expensive. Locally, we only use it routinely for Early Infant Diagnosis (EID) through KEMRI as research clearly shows general improvement in quality of life if ART is initiated early for HIV +ve infants. Remember too that the virus tends to 'hide' in the brain and can thus cause some CNS-deficiency if treatment is delayed.

p24 is no longer widely used due to its lack of sensitivity and the fact that it is only applicable at a specific time in the course of infection, just before the body begins to mount an immune response.

I hope this is clear now my friends. Kama kuna maswali mengine, yalete pia. @Lolest! uliza yako pia mblo.

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Question 1 is well answered so i will not repeat and will go to question 2 thanks @Rankaz13

It is [NOT] true that a patient with undetectable viral load cannot transmit infection but [IT IS VERY RARE]. At this point let me say that most of the replication is occurring in the LYMPHOID tissues while we are only sampling the blood tissue. However, you all know it depends on the route of transmission.
There are also some people whom HIV infection with some viruses (CCR5 tropic) is impossible. For instance 1-2% of Caucasians with delta32 CCR5 do not express a functional CCR5 and cannot be infected by CCR5 tropic viruses. In African populations (some in EA) we have delta24 CCR5 and the last time i did a flow cytometry experiment to assess expression it behaved the same way but this genotype but it is not well studied. There are also HLA variants that confer protection especially in discordant couples.

Good info BGL but boss,... come srow, come srow....

This is my question/scenerio

(not their real names)

Otieno hooks up with Nduku. Otieno suggests that they both go for a HIV tests. Nduku agrees, but has a hidden secret. She is positive but and has been on treatment for some time and viral load/count is undetectable. So she expects to show up as negative.... Even if they decided to go for repeat tests after six months, the results for Nduku will be the same as long as she remains on treatment.

Is this a likely possibility?

I think not. As long as the virus is there, even though the levels be low, the body will always mount an immune response to it i.e antibodies. And since the tests we routinely use are antibody-based, there you are.

What say you @BGL?

The new strain is a "recombinant" virus - a cross of two viruses that meet in an infected person.

The two viruses, known as 02AG and A3, are the two most common strains in Guinea-Bissau, West Africa. The recombinant strain is called A3/02 and so far has only been seen in the region.

A single shot of antiretroviral drugs protected lab monkeys from the AIDS virus for weeks, according to two US trials released on Tuesday that open the way to tests on humans.

In separate work, two teams of virologists found that monkeys which received a monthly injection of a prototype drug were completely shielded from the simian equivalent of HIV.

The research builds on previous trials showing that people who take a small daily doses of antiretroviral drugs can slash their risk of being infected by an HIV-positive partner by more than 90 percent.

A new gene therapy approach that engineers a person's T-cells so that they become resistant to the human immunodeficiency virus has shown early signs of success, researchers said Wednesday.

Also called gene editing, the process acts like molecular scissors to snip off an entry portal for HIV so the virus cannot enter these key immune cells.

Once the cells lack the CCR5 protein, the immune system behaves much the way it does in a rare set of people -- about one percent of the population -- who are born with a genetic mutation that prevents them from getting HIV.

From a layman's perspective what happens with such research outcomes, over the years I've read about a few breakthroughs but none has yet to be commercialized.

Indeed. Studies on so-called PrEP been going on for a while now, initially comparing use of TDF alone vs. TDF+FTC combination. The latter was seen to be superior. Once further studies, now ongoing, are finalized and results released, NASCOP will then come up with national guidelines and avail drugs for the same. Many questions, obviously, are yet to be addressed.