The flu has added a drastically perilous element to The Walking Dead: suddenly everyone is at risk, not just from one bitten human in their midst, or the myriad of walkers at the gates, but from every other human in the compound. No epidemic in human history has been 100% deadly. But some, like the Black Plague, killed from 2/5s to 3/5s of the population in some areas. Our heroes and storylines will have their work cut out for them.
There's a new character with some medical knowledge on the show, and Herschel with his veterinary skills will be even more important than ever. Is he the one who burned the two bodies we see at the end of the episode? Although differences of opinion and temperament in the characters have always been a central part of the series, the flu - and what should be done to shield healthy people from its consequences - could split the community wide open, including people and relationships that go back to the beginning of the series.
Of course, since the flu is no more real - has no more literal historical precedent - than the zombie-making plague that animates the whole series, anything is possible in terms of the flu's reach and deadliness. In our real world, far less than 50% usually contract any flu, and most people do not die from it. Any of our characters could either be immune, or have enough resistance to recover from the infection.
In the meantime, I'm feeling a little tickle in my throat - I'm going to have a hot tea with honey.