In Mexico, the girl was in serious condition in a hospital in Torreon in the neighboring state of Coahuila, the health ministry said in a statement Friday. It said she had initially been treated with an anti-flu medication.
It was not known how the girl contracted the virus. Investigators were testing wild birds in the vicinity of the girl’s home, the statement said.
The health ministry said the risk to the general population from the virus was considered low.