A pharmaceutical composition comprising a therapeutically effective amount of a compound having anti-viral activity represented by the structure of formula I: or a salt or a solvate thereof, wherein Y represents a group -NR 1 R 2; wherein either (i) R 1 represents an optionally substituted alkyl, alkenyl or alkynyl group; and R 2 represents an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; (ii) R 1 represents a hydrogen atom and R 2 represents an optionally substituted alkyl, alkenyl, alkynyl or cycloalkyl; (iii) R 1 and R 2 together with the interjacent nitrogen atom represent a non-aromatic heterocyclic group selected from the group consisting of piperazinyl, morpholinyl, thiomorpholinyl, and morpholinosulphonyl or an amino group derived from an optionally substituted amino acid ester; or (iv) R 1 represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; and R 2 represents an -X(=Z)-A group, wherein X represents a carbon atom, a sulfur atom, a sulfoxide group S=O, or a group PR 3, P-O-R 3 or P-N(R 4) - R 3, where R 3 and R 4 each independently represent a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; Z represents an oxygen atom, a sulfur atom or a group NR 5, where R 5 represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; and A represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group, or a group selected from N(R 6) 2, NHNH 2, NR 6 NHR 6, NR 6 N(R 6) 2, OR 6, SR 6, 10α-dihydroartemisinyl, OR 7 and NR 6 R 7, where each R 6 independently represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group, and R 7 represents a bond attached as a substituent to R 5 or R 1 which together with the interjacent groups represent an optionally substituted heterocyclic group, for use in treating a viral infection or suppressing viral replication. (i) R 1 represents an optionally substituted alkyl, alkenyl or alkynyl group; and R 2 represents an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; (ii) R 1 represents a hydrogen atom and R 2 represents an optionally substituted alkyl, alkenyl, alkynyl or cycloalkyl; (iii) R 1 and R 2 together with the interjacent nitrogen atom represent a non-aromatic heterocyclic group selected from the group consisting of piperazinyl, morpholinyl, thiomorpholinyl, and morpholinosulphonyl or an amino group derived from an optionally substituted amino acid ester; or (iv) R 1 represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; and R 2 represents an -X(=Z)-A group, wherein X represents a carbon atom, a sulfur atom, a sulfoxide group S=O, or a group PR 3, P-O-R 3 or P-N(R 4) - R 3, where R 3 and R 4 each independently represent a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; Z represents an oxygen atom, a sulfur atom or a group NR 5, where R 5 represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group; and A represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group, or a group selected from N(R 6) 2, NHNH 2, NR 6 NHR 6, NR 6 N(R 6) 2, OR 6, SR 6, 10α-dihydroartemisinyl, OR 7 and NR 6 R 7, where each R 6 independently represents a hydrogen atom or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl or aralkyl group, and R 7 represents a bond attached as a substituent to R 5 or R 1 which together with the interjacent groups represent an optionally substituted heterocyclic group, for use in treating a viral infection or suppressing viral replication. for use in treating a viral infection or suppressing viral replication.