Fixes an issue where the "variant" field can be inferred to have a dtype of integer when a clade (or "variant") name in flu is an integer (e.g., clade "1" in H1N1pdm nomenclature), causing a parsing error when a non-integer clade name is encountered later in the same file.
Fixes an issue where the "variant" field can be inferred to have a dtype of integer when a clade (or "variant") name in flu is an integer (e.g., clade "1" in H1N1pdm nomenclature), causing a parsing error when a non-integer clade name is encountered later in the same file.