There are two cases of undetectable HIV viral load, the first is that a healthy person can have his or her blood tested for HIV viral load because he or she is not infected with AIDS, so naturally the HIV viral load is undetectable in the blood. The second is that after the person has been infected with AIDS, he or she insists on taking antiviral drugs to suppress the replication of the virus, so that even if the HIV viral load in the body is checked by blood sampling, it can be lower than the lower limit of detection, which is less than 20copies/ml. Therefore, once a patient is infected with AIDS, he should take antiviral drugs in time for treatment, so that the virus can be lower than the lower limit of detection through antiviral treatment.