What does undetectable really mean?


My roomate is hiv positive. She has had undetectable levels for over two years. She says that her doctor says that she cannot transmit the virus to anyone and that it would take many months off of medication for the viral load to reach a point that she could infect someone. Is this tue? I have read on this website about viral load blips(?), why would a doctor tell a patient that they basically cannot infect others as long as they are undetectable, if this is not really true?

Please give your best advise.


Good question. Undetectable means that tests that look for the virus in the blood can not find any to count. All such tests have a lower limit of detection. That is, a threshold below which it is not able to find virus (sort of like a needle in a haystack).

We know that folks with undetectable HIV in their blood rarely transmit their HIV to others. Now I did not say it was impossible. Some people may have more HIV in their genital secretions than in their blood. Others may miss a few days (yes days, not months) of their HIV meds and experience a spike in their HIV levels. And, as you say, blips happen, but usually these are very transient bumps to still low levels of virus. Still, transmission from a person on meds with an undetectable level of HIV in the blood is worthy of publication as a report in a medical journal it is so unusual.

Doctors inform their patients of the facts and these are them. I have a number of patients who are like your roommate and who are in monogamous relationships with an HIV-negative person. Together we have long talks about risks and some decide that given the data they are willing to forego condoms. Others do not. And still others consider having the negative parter take PrEP. It is a grown up decision to be made with information.