Its capsid is a cylinder - slightly larger at one end, appears round due to a lipid envelope. There is a spike consisting of two proteins. Multimeric chromosomes and proteins are made. HIV - is less pathogenic. Secondary means - free virions.
Body fluids have low number of free viruses - even the blood.
Repeated exposures are a major factor. The crown of the gp120 is conserved, other parts vary considerably - there are four C and five V domains. V3 is the most variable domain. When the variance is 10 to 17.3 - the two viruses are not related. The gp120 and gp41 stay on the outside.