Finally, the incubation period of COVID-19 is approximately 5 days, and the median time between the onset of illness and the first measurement was approximately 8 days; it is possible that the IFN-γ levels in the blood were elevated during the incubation period of COVID-19, but the absence of symptoms precluded the measurement of IFN-γ levels in the blood during that time. The gene discussed is IFNG; the disease is COVID-19.