I haven't really been keeping tabs of the specific situation in Japan, but it sounds like they're one of the countries that's a little behind in terms of getting locked down etc. It feels like it's only a matter of time though.
Toei say that none of the other cast or crew members are reporting symptoms at this time, although they also said that Rio was still filming on-set as recently as Friday. They don't mention whether the rest of the cast and crew are now isolating, but hopefully they are
Toei have, however, confirmed that as of yesterday their studio facilities have been closed and will undergo a complete disinfecting. This means that it's now the decision of health officials as to when it can re-open.
Apparently the studio space was being used by four productions at the time, but only three of them have been named: Kiramager, along with 'Tokuso9' and 'Keishicho Sosaikkacho 2020' (both seem to be police procedurals). It would seem like an obvious guess that Zero-One would be the fourth, which I guess means at the very least they can't use their standing sets (Aruto's office, that room with the fancy 3D printer that makes Progrise keys, etc).