Discloses the use of a composition comprising shortened fibres of poly-&bgr；-1&rarr；4-N-acetylglucosamine (&ldquo；sNAG nanofibers&rdquo；) in the manufacture of a medicament for treating a viral infection or a viral disease in a human subject having a viral infection or a viral disease, wherein the treating comprises topically administering the composition comprising the sNAG nanofibres to the human subject, and wherein (i) more than 50% of the sNAG nanofibres are between about 1 to 15 &mu；m in length, or (ii) the average length of the sNAG nanofibres is less than 15 &mu；m.
