CD69 and infection: Further, the percentage of peripheral blood NK cells expressing CD69, a marker associated with activation and tissue trafficking/residency [50–52], significantly increased from pre-infection (mean 3.56%; range: 1%-5.93%) to 3DPI (mean 17.96%; range: 3.84%-27.55%) and declined immediately afterwards (adjusted p-value < 0.0001) (Fig 1D).