I don’t know that it’s that dire. “More deadly” doesn’t mean a disease will kill more people. A virus or bacteria has to be infectious enough to spread quickly, not kill enough people that are infected to allow people to spread it without causing it to die with them, but still be deadly enough to be noteworthy. COVID ticked all of those boxes. Bird Flu might as well, if it becomes human-to-human transmissible (which seems more likely every day), but I guess we’ll see.