What is a 'viral load'?

What is a 'viral load'?

Charles Farthing (Chief of Medicine, AIDS Healthcare Foundation) gives expert video advice on: Why do I need to take lab tests if I have HIV? and more...

A viral load simply means the quantity of virus in the blood, the load of virus in the blood. And it is explained in terms of number of copies of virus per millilitre or cc of blood. So a viral load of a thousand copies of virus per cc of blood or per ml is a low viral load. A viral load of greater than 10,000 copies of virus per cc of blood is a high viral load. It can be much higher. A patient who has just been infected could have a viral load of 6 million copies of virus per cc of blood. A patient who is on therapy should have an undetectable viral load. And that is usually expressed as less than 50 copies of virus per cc of blood. The reason it's not read down to zero is that the assays are not very accurate between zero and fifty as to how many copies of virus there actually is. So, usually undetectable is read as less than fifty copies of virus per cc of blood.