Ducks are seen inside a poultry farm in Castelnau-Tursan, France. —Reuters The bird flu virus that spreads among wild birds, poultry and mammals could lead to a pandemic worse than Covid-19 if the virus mutates to be transmitted between humans, the head of the respiratory infections center at France’s Pasteur Institute said. Highly pathogenic avian influenza, commonly called bird flu, has killed hundreds of millions of birds in recent years, disrupting food supplies and driving up prices, although human infections remain rare. “What we fear is that the virus adapts to mammals, and especially to humans, it can be transmitted