How long after initial infection is HIV contagious but test results still show negative?

I would assume it would be contagious immediately, but... I think, and don't quote me on this, that it takes up to 6 months or so for it to show up on a test. Yup, HIV in general and STD's in general are bad news. Which is why sex education and prevention of all of this is important.

Someone who is infected today would be capable of spreading the virus to others by tomorrow, but may not test positive for 3 months, (or 6 months in very rare cases) and probably won't see symptoms for several years. Yes, it is a bad situation. Many people pass the virus on before they learn that they themselves are infected. Lack of symptoms may give people a false sense that they are healthy, regardless of their risky behavior, and that there is no need for them to be tested. You can't tell if someone is infected just by looking at them.

If you contract the disease it is possible to spread it shortly there after. It is scary and people may not know they have it for a while because the virus can lay dorminant inside their t-cells for long periods of time before it starts to replicate. So yes it is a bad situation, even scarier is some people can have the virus floating around in their body but never be infected, the reason being that the virus attacks specific immune cells call t-lymphocytes (t- cells) in order to actually infect the cell it has to bind to the cells surface and pass through the cell membrane where is can use the cells internal structures to replicate. some people are genetically predispositioned with an abnormality of the surface of their t- cells making it impossible for the virus to pass through the membane, therefore they are never infected but can still be carriers, how scary is that.