What I have heard and I would like someone in the industry to confirm, is mostly personnel from long term care facilities or old folks home. Low pay, relatively low skill jobs. Lots of immigrants work there. In Canada, in a few cites, the armed forces were called in (medical pers) to assist as a lot of workers got either scared or infected and old people were abandonned and died in those homes - the staff got scarcer and scarcer as the caretakers got contaminated and the staff level dropped.