CONMEBOL, the South American football confederation, have asked the Mexican football federation to explain what measures they will be taking to protect players visiting from overseas to play in Copa Libertadores matches in the swine flu-affected country.
Nicolas Leoz, the president of CONMEBOL wrote to his Mexican federation counterpart Justino Compean asking him to clarify what steps were being taken.
"CONMEBOL expresses deep concern for the epidemic outbreak that has unfortunately affected some areas and inhabitants of Mexico," Leoz wrote.
"We ask to be told which measures we should take in this serious situation to save the physical form of the players, the coaching staff and club officials."
San Luis made it into the round of 16 yesterday by beating Libertad 2-0 in Paraguay, while giants Guadalajara will achieve the same goal if they clinch at least a draw against Everton in Chile on Wednesday.