Concurrent partnerships drive epidemic HIV spread
HIV spreads fastest not where people have the most lifetime partners, but where people have overlapping long-term relationships at the same time. Because viral load is extremely high in the weeks after infection, a newly infected person in a concurrent network can pass the virus to several partners before anyone gets sick, which links many people into a single chain of transmission. Serial monogamy with the same total number of partners traps the virus inside one relationship at a time.
