These shortages often occur in summer/holiday seasons when the number of donors is reduced and the risk of epidemiological outbreaks, such as West Nile Virus, can temporarily reduce the number of eligible donors.
Dawn l-iskarsezzi ta' sikwit iseħħu fis-sajf/staġuni tal-vaganzi meta n-numru ta' donaturi jonqos u r-riskju ta' tifqigħat epidemjoloġiċi, bħall-virus tal-West Nile, jistgħu jnaqqsu n-numru ta' donaturi eliġibbli b'mod temporanju.