Antiviral drugs such as oseltamivir (trade name Tamiflu) and zanamivir (trade name Relenza) are neuraminidase inhibitors that are designed to halt the spread of the virus in the body. These drugs are often effective against both influenza A and B. The Cochrane Collaboration reviewed these drugs and concluded that they reduce symptoms and complications. Different strains of influenza viruses have differing degrees of resistance against these antivirals, and it is impossible to predict what degree of resistance a future pandemic strain might have.

Figure 3. Antiviral drugs Tamiflu (oseltamivir) and Relenza (zanamivir).