EFHD2 and COVID-19: The PAH DEGs related to exosomes include several membrane receptors (S1PR1, PECAM1, PSEN2, MYADM, EFNB1, EFHD2, NOTCH4) that might be expressed in PAH cells after being delivered by exosomes, which have been involved in the interaction with microorganisms like salmonella, legionella, HPV, Escherichia coli, and Staphylococcus aureus, and the activation of signaling pathways like Notch, efferocytosis, coronavirus disease (COVID-19), phagosome, MAPK, HCV, HPV, and salmonella infection, B cell receptor, and autophagy.