... concentrations of melanin in dark-skinned individuals shield the keratinocytes from the ultraviolet radiation required to generate vitamin D in skin [38]. In addition, the production of vitamin ... the percentage is higher in the winter, in the aged, in the obese, in the sun-deprived, in the dark-skinned, and in more poleward pop-ulations [40,41]. However, seasonal variation of vitaminD ... remember that the incubation period only tells us what the serial interval shouldbe, not what it is. Furthermore, induction of human infection in the laboratory only tells us such infection is possible;...