A mutation in newly emerged H7N9 influenza can render it resistant to the only class of drugs active against the virus, without affecting its ability to spread in animals. This finding, published in a study this week in Nature Communications, reveals that unlike seasonal flu, drug-resistant H7N9 can replicate in animals as efficiently as its non-resistant counterpart.
Nicole Bouvier and colleagues analysed mutated H7N9 virus, isolated from a patient in China, for its resistance to drugs and infectivity. They found that the virus was highly resistant to antiviral drug oseltamivir, also known as Tamiflu. In addition, it could infect cultured human cells and spread between laboratory animals as efficiently as its non-mutated counterpart. This is unusual, as it is known that when seasonal influenza viruses gain resistance to drugs, it usually happens at a cost to the virus - the cost being a reduced ability to transmit between hosts and to grow within them.
H7N9 influenza emerged earlier this year in China and has caused over 130 human infections so far. As a vaccine against this strain of influenza is not available yet, antiviral drugs are at the moment the only means of controlling infection with H7N9. It is known that treatment with antivirals can lead to development of drug resistance in influenza, and this study further underscores the need of prudent use of antivirals in H7N9 influenza infections.