If it seems like half the people you know have come down with COVID-19 recently, you’re not alone. Southern California is in the midst of a sustained wave of coronavirus cases that has been building since the spring, and with two new wildly contagious variants bursting onto the scene, the wave is showing no signs of ending. They’re actually subvariants of omicron, the strain that caused last winter’s huge surge. They don’t necessarily cause more severe disease, the difference is that they’re…