Emergencies are exceptions, and there are measures in place for such occasions, like declaring a state of emergency. The norm shouldn’t be shaped by the mere possibility of a worst-case scenario, especially when there are everyday medical needs that still go unmet
From a health security perspective, it’s not really a good idea to deny immigrants (legal or otherwise) healthcare because if they get sick, that illness can spread within the community. Unfortunately viruses don’t care about your citizenship status