If one developed meningitis or encephalitis during ARS would it (they) be infectious to others. If so, what would the mode of potential transmission be? THanks...
You are highly infectious to others if you have Acute Retroviral Syndrome (ARS), regardless of whether your HIV infection manifests itself as meningitis, encephalitis or even just thrush. It's not the clinical manifestation of HIV that makes you a risk to others, it's the fact that you've been recently infected. In general, newly-infected people have the highest viral loads (amount of HIV in the blood), and that is what determines your infectivity to others.
If you or someone you know is having these symptoms (meningitis, etc), then you need to get tested ASAP. And for God's sake, do not have sex-- even protected sex-- with anyone just now, so you can avoid the risk of passing the virus along. This is exactly why the epidemic keeps going.