NEW : Spokeswoman : Two tested in San Antonio for MERS ; none has symptoms . A case in the U.S. brings the total to 4 countries affected . CDC official : `` We do n't know as much as we 'd like so far '' 18 San Antonio airlines are coordinating with health officials over cases in U.S .
NEW : Spokeswoman : 4 tested in San Antonio for MERS ; none has symptoms . A case in the Netherlands brings the total to 18 countries affected . CDC official : `` We do n't know as much as we 'd like so far '' Two U.S. airlines are coordinating with health officials over cases in U.S .