|H7N9 under electron microscope|
It’s common knowledge that influenza viruses mutate. They change and adapt quickly. One of these mutations, the one that enables them to become drug resistant, comes at a high price to the virus. It weakens it.
Almost universally, flu viruses become less virulent when they become drug resistant. In becoming drug resistant, their ability to replicate and its effectiveness is usually considerably reduced.
This is not the case with H7N9. Patients suffering with H7N9 have been treated with Oseltamivir (Tamiflu) and the virus has shown it is resistant in several patients. Normally this would improve the prognosis for the patient, but it hasn’t. Patients have still suffered a long duration of illness and poor clinical outcomes generally, with some patients still dying from the disease.