The novel coronavirus has developed a number of worrisome mutations, resulting in multiple new variants popping up around the world. Now, a new study sheds light on how the virus mutates so easily and why these mutations help it “escape” the body’s immune response.

The study researchers found that SARS-CoV-2, the virus that causes COVID-19, often mutates by simply deleting small pieces of its genetic code. Although the virus has its own “proofreading” mechanism that fixes errors as the virus replicates, a deletion won’t show up on the proofreader’s radar.