As we leave behind the March rerun lull and careen headlong into May “sweeps” and season finale territory, I want us to pause for a minute and consider an epidemic that threatens to destroy the situation comedy as we know it.

The lovable bundle of joy that is the sitcom is in deep trouble: one by one, the stars of sitcoms seem to be abandoning their shows a season or two shy of the series finale.

It all started when Zach Braff, who starred as J.D. on “Scrubs,” left the show in its eighth season, while the show continued on for a ninth without him.

And while Charlie Sheen didn’t technically abandon “Two and a Half Men,” on some level he should have realized that his out-of-control partying and subsequent media antics would get him fired from the show.

Now Steve Carell has left “The Office.” And Alec Baldwin is making noise about leaving “30 Rock.”

If “Scrubs” is any indication, the loss of a sitcom’s original star creates a vacuum of power and charisma so massive that almost any reconfiguration, any new cast member brought in as a “replacement,” will undoubtedly be sucked into the black hole. And the show along with it.

Carell’s character, Michael Scott, will appear in his final “Office” episode on April 28, according to E!Online.

The show, which was officially picked up for next year, will then finish out this season with four more episodes starring Will Ferrell as the temporary “boss.” No word yet on the permanent replacement, though rumors abound that Mindy Kaling, the “Office” writer who also plays Kelly Kapoor, will fight for the promotion.

For his part, Baldwin told CNN in July that he plans to leave “30 Rock” next year when his contract with the show expires (he also hinted that the show might end at that point). In a Q&A this week for her new book “Bossypants,” “30 Rock” creator Tina Fey called what she feels is Baldwin’s bluff. “[Baldwin] saying he’s officially done [with “30 Rock”] is the first indication that he’s staying,” she said.

I want to believe her, but I can’t help feeling that it’s not looking good.

What now?

Whether or not Baldwin actually leaves “30 Rock” next year, both he and Carell seem to be attracted like moths to the glowing Hollywood cinema searchlights.

This is understandable: both actors have made successful films in the past few years — Carell’s “40-Year-Old Virgin” (2005) and Baldwin’s “It’s Complicated” (2009) come to mind. Movies are more glamorous than television. And they pay much more.

But what, then, is the lamentable fate of the recently renewed sitcom that has lost its most charismatic star, its household name, its lead character? Its Michael Scott? Its Jack Donaghy?

I’m inclined to think that the loss of the star causes some sort of trauma-induced confusion on the part of the writers and producers of the show; it deludes them into believing that the show can continue to succeed without said star. This seems to have been the thought process governing the twilight years of, at least, “Scrubs” and the more recent “Two and a Half Men” fiasco.

“It’s an ensemble cast,” the writers and producers might say to themselves. “If we can just write out [name of star] in a witty-yet-poignant enough way, if we can just bring in a new cast member or two, and if we can just get [name of star] to agree to guest star a couple of times to ease the transition, everything will be fine, right?”

Wrong: everything will NOT be fine. At this point, the show cannot — and should not — go on.

If the show has had a healthy run (about six or more seasons) and its lead cast member is burned out, maybe that’s a good indication that the show itself is burned out as well. The producers, writers and actors should invest their time and energy (not to mention money) in new, more promising ventures.

Much as it pains me to suggest that my favorite shows should draw to a close immediately upon losing their biggest stars, I’d rather see shows finish abruptly and strongly than straggle and sputter to the finish line.

That being said, I’d rather watch this sputtering than a test pattern (do they even still have those?).

And I’d rather watch a test pattern than “Outsourced.”

(We’ll miss you, Michael Scott.)