To test the hypothesis that milk from breastfeeding mothers with COVID-19 has higher levels of cytokines related to Th cells (IL-4, IL-17, IFN-γ, IL-2, and TNF-β) than milk from breastfeeding mothers without SARS-CoV-2 infection, Demers-Mathieu et al. analyzed 40 milk samples from 10 breastfeeding mothers with a COVID-19 diagnosis confirmed by RT-PCR, 10 breastfeeding mothers with viral symptoms suggestive of COVID-19, and 20 breastfeeding mothers without infection. Here, IL17A is linked to infection.