Q. May one invite someone for the seder or Yom Tov meals if the guest does not have any symptoms and would have nowhere else to go, due to everyone else’s reluctance to invite people during this time? May one trust in the merit of the mitzvah to protect him? 
A. The question has significant variables. Although the guest may not have any symptoms yet, if he was exposed to the virus he may be a carrier. Not only the health condition of the visitor is an issue, so is the status of the hosts as they may also be carriers or aged and frail and susceptible to became easily ill.
Horav Shlomo Miller’s Shlit’a opinion is that a great amount of common sense is necessary to render a correct psak and a competent Rabbi familiar with both, the host and the guest should render a decision.
One may definitely try to find other ways or proper accommodation for the ones in need. The community or friends may provide a location where a few needy guest can celebrate the seder with proper separation or in different rooms.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a