A hinge cover is provided for a refrigerator door hinge so as to hide the hinge screws. The electric discharge detector includes a counter for generating a sample clock having a frequency greater than the frequency of the gate signal, and a comparator for receiving the gap voltage and determining that a fall in the gap voltage is larger than a specified voltage difference in each sample clock. Detection of scattered radiation that exhibits a Raman shift characteristic of the pathogen is an indication that the pathogen occurs in the sample.