A compound of Formula I: or a pharmaceutically acceptable salt thereof; wherein: each of R 1 and R 7 is independently H, halogen, OR a, (C 1 -C 8)haloalkyl, (C 3 -C 8)halocycloalkyl, CN, N 3, (C 1 -C 8)alkyl, (C 3 -C 8)cycloalkyl, (C 1 -C 8)substituted alkyl, (C 3 -C 8)substituted cycloalkyl, (C 2 -C 8)alkenyl, (C 2 -C 8)substituted alkenyl, (C 2 -C 8)alkynyl or (C 2 -C 8)substituted alkynyl, wherein the substituent is selected from the group consisting of -X, -R b, -OH, =O, -OR b, -SR b, -S -, -NR b 2, -N + R b 3, =NR b, -CX 3, -CN, -OCN, -SCN, -N=C=O, -NCS, -NO, -NO 2, =N 2, -N 3, -NHC(=O)R b, -OC(=O)R b, -NHC(=O)NR b 2, -S(=O) 2 -, -S(=O) 2 OH, -S (=O) 2 R b, -OS(=O) 2 OR b, -S(=O) 2 NR b 2, -S(=O)R b, -OP(=O)(OR b) 2, -P(=O)(OR b) 2, -P(=O) 2, -P(=O) 2, -P (OR b)(O -), -C(=O)R b, -C(=O)X, -C R b, -C OR b, -C O -, -C OR b, -C SR b, -C SR b, -C NR b 2, -C NR b 2, -C( =NR b)NR b 2, where each X is independently a halogen: F, Cl, Br, or I; and each R b is independently H, alkyl, cycloalkyl, aryl, arylalkyl, or a heterocycle; R 2 is OR a; R 3 is halogen or N 3; each R a is independently H, arylalkyl, aryl, (C 1 -C 8)alkyl, or (C 3 -C 8)cycloalkyl; R 4 is H, =O, OR a, N(R a) 2, N 3, CN, S n R a, halogen,(C 1 -C 8)haloalkyl, or (C 3 -C 8)halocycloalkyl; R 5 is H, =O, OR a, N(R a) 2, N 3, CN, S n R a, halogen, (C 1 -C 8)haloalkyl, or (C 3 -C 8)halocycloalkyl; each n is 0, 1 or 2; and each R 6 is H, aryl, arylalkyl, or wherein W 1 and W 2 are each, independently, OR a or a group of the Formula la: wherein: each Y is independently a bond or O; M2 is 0, 1 or 2; and each R X is H, halogen or OH, for use in a method for treating an Orthomyxoviridae infection in a mammal. each of R 1 and R 7 is independently H, halogen, OR a, (C 1 -C 8)haloalkyl, (C 3 -C 8)halocycloalkyl, CN, N 3, (C 1 -C 8)alkyl, (C 3 -C 8)cycloalkyl, (C 1 -C 8)substituted alkyl, (C 3 -C 8)substituted cycloalkyl, (C 2 -C 8)alkenyl, (C 2 -C 8)substituted alkenyl, (C 2 -C 8)alkynyl or (C 2 -C 8)substituted alkynyl, wherein the substituent is selected from the group consisting of -X, -R b, -OH, =O, -OR b, -SR b, -S -, -NR b 2, -N + R b 3, =NR b, -CX 3, -CN, -OCN, -SCN, -N=C=O, -NCS, -NO, -NO 2, =N 2, -N 3, -NHC(=O)R b, -OC(=O)R b, -NHC(=O)NR b 2, -S(=O) 2 -, -S(=O) 2 OH, -S (=O) 2 R b, -OS(=O) 2 OR b, -S(=O) 2 NR b 2, -S(=O)R b, -OP(=O)(OR b) 2, -P(=O)(OR b) 2, -P(=O) 2, -P(=O) 2, -P (OR b)(O -), -C(=O)R b, -C(=O)X, -C R b, -C OR b, -C O -, -C OR b, -C SR b, -C SR b, -C NR b 2, -C NR b 2, -C( =NR b)NR b 2, where each X is independently a halogen: F, Cl, Br, or I; and each R b is independently H, alkyl, cycloalkyl, aryl, arylalkyl, or a heterocycle; R 2 is OR a; R 3 is halogen or N 3; each R a is independently H, arylalkyl, aryl, (C 1 -C 8)alkyl, or (C 3 -C 8)cycloalkyl; R 4 is H, =O, OR a, N(R a) 2, N 3, CN, S n R a, halogen,(C 1 -C 8)haloalkyl, or (C 3 -C 8)halocycloalkyl; R 5 is H, =O, OR a, N(R a) 2, N 3, CN, S n R a, halogen, (C 1 -C 8)haloalkyl, or (C 3 -C 8)halocycloalkyl; each n is 0, 1 or 2; and each R 6 is H, aryl, arylalkyl, or wherein W 1 and W 2 are each, independently, OR a or a group of the Formula la: wherein: each Y is independently a bond or O; M2 is 0, 1 or 2; and each R X is H, halogen or OH, each Y is independently a bond or O; M2 is 0, 1 or 2; and each R X is H, halogen or OH, for use in a method for treating an Orthomyxoviridae infection in a mammal.