It is tough, but it's not rare! Generally you do have paid sick leave in Japan, of course, but as you know most Japanese won't take it unless absolutely necessary. Unfortunately it's quite common to have no paid sick leave in the eikaiwa world :(
Wow! o__O; ...
Well at times like that you wish yourself back to good old Germany where people even get a "Krankenschein" from the doc when they're not sick at all (T__T)