If you and your boo are both HIV positive, and you’ve deep-sixed the condoms because you think the risk of superinfection is a myth, yet another new report may give you pause.

In May, AIDS reported that a California man was superinfected with drug-sensitive (“wild type”) HIV four months after contracting a drug-resistant strain. Lab work proved he hadn’t gotten both strains simultaneously, and the new infection spiked his viral load from 2,400 to nearly 200,000, as his CD4s dropped from the 800s to the 200s in a year—courtesy of the more virile “wild type.”

With most viral diseases, the immune system builds barriers to superinfection (that’s why mumps and measles strike only once). But scientists have long deemed HIV reruns possible, even likely, because the virus acts like the common cold or flu—constantly mutating, or reinventing itself. The immune system reads each new version as unique, so your response to the first strain doesn’t protect you against any sequel.

Over the past year, only a handful of HIV superinfections have been confirmed by lab analysis—precisely why some HIVers say that same-serostatus skin-on-skin sex is a risk worth taking.

Others warn that superinfection could speed disease progression or help spread drug-resistant HIV, limiting treatment options. In one case, the superinfection strain differed by only 12 percent from the original HIV but still evaded the immune system’s detection. As Joseph Sonnabend, MD, says, “There is a documented danger, though no one can quantify it. It means positive couples shouldn’t assume safe sex doesn’t matter.”