Health Sex and sexual health HIV What is serodifferent What does serodifferent mean? Serodifferent is also known as serodiscordant. When a couple is serodifferent, this means one person is living with HIV and the other person is HIV-negative. How can a couple be serodifferent? If the person living with HIV is on effective treatment, his viral load will drop and he will be HIV-undetectable. This means he cannot pass on HIV. You are not at risk from HIV if you have sex with someone who is HIV-undetectable. What if your partner isn't HIV-undetectable? If the person living with HIV doesn’t have an undetectable viral load, it is important that an HIV prevention method is used. This could be in the form of condoms, or taking the HIV prevention drug, PrEP. It is important that the HIV-negative partner still goes for regular HIV tests. It is recommended by Public Health England that sexually active gay men have a HIV test at least every 12 months.