For every person who gets HIV permanently, the body probably fights off four or five infections that just vanish on their own.
March 24, 2026
Original Paper
Accounting for barriers to HIV infection in the recipient partner reveals frequent transient infections and explains transmission risk under viral suppression
medRxiv · 10.64898/2026.03.20.26348904
The Takeaway
A new mathematical model reveals that HIV frequently begins to replicate in a new host but is 'stochastically extinguished' by biological barriers before it can become established. This discovery explains why transmission risks are lower than expected and identifies a hidden phase of 'near-miss' infections that were previously unobserved by medical science.
From the abstract
Background: HIV transmission is characterised by a low per-act probability, a relatively high proportion of multiple variant transmission events, and a plateauing of transmission risk at high viral loads. No existing mechanistic model can simultaneously recapitulate all of these observations, thereby limiting our ability to predict unobserved transmission phenomena and evaluate prevention strategies. Methods: We developed a suite of mathematical models that encode an empirically plausible set of