A mutated strain of the H7N9 influenza virus that infects humans is resistant to the antiviral drug Tamiflu. Becoming drug resistant does not appear to affect the ability of the virus to infect cells.
Chinese health authorities reported a new case of H7N9 bird flu on October 15.
That virus sickened 135 people earlier this year, killing 44. Most of the cases occurred in March and April before poultry markets in the country closed to limit the virus’ spread, but two cases were recorded in July.
It is too soon to tell if the new case represents a resurgence of the flu or is another sporadic case.