From an epidemiologic standpoint, this year is different from 1984: apparently pennant fever evolves between outbreaks, in much the way that viruses change every time it seems they’ve been trapped and eradicated.

For one thing, the disease has changed its incubation period: it showed up later in the season this time. Five years ago, the combine of glazed wonder and giddy jubilation all but paralyzed the city as early as late July; this year, September was well settled in before the outbreak began to reach quarantinable proportions.

Of course, the difference has much to do with the Cubs themselves. The 1984 team looked like a powerhouse by mid-season; the 1989 Cubs, though a fundamentally better team at every position, took longer to jell into the scrappy late-inning winners they’ve turned out to be. But there are other factors at work, proving that even amid conditions unsanctioned by the medical authorities, some degree of autoimmunization is possible. The spread of pennant fever has been slowed by two realizations made possible by our 1984 bout: the collective understanding that more ought to happen this time, and the emerging knowledge that the disease need not lie dormant for four decades between appearances. In 1989, shock is no longer a surefire symptom of pennant fever.

Still, the disease’s last phase remained the same. In 1984, after the 81st game had been played at Wrigley Field, three-quarters of the fans refused to leave the park until the team–many of whom had already begun to change from their uniforms–returned for a delirious extended curtain call, which consisted of strolling the playing field and basking in the cheers and thanks of the crowd. Only three of the current Cubs were around for that extraordinary show of support, which would be unimaginable in nearly any other city; consequently, when last Sunday’s home finale ended with a similar display of adulation, almost all the players were genuinely amazed and gratified by the scene around them. They simply hadn’t seen this symptom before.

(Meanwhile, from the stands and the rooftops and the TV screens around town, the delightful irreality of the 1989 Cubs topping their division was enhanced by the patently incongruous sight of half-undressed ballplayers loping around the outfield to wave at the crowd–a sight akin to actors returning to the stage when the play is ended, dripping makeup, out of character, and proceeding to converse with the remaining theatergoers as if they were in fact equals in the preceding drama.)

Here’s another symptom: I have noted in myself a sharpening of the senses, a penchant to hang onto each pitch and strategic adjustment with a clarity and singlemindedness that surprises me. And I know, from speaking to others, that I’m not alone in this. It began with the Mets series that opened September (technically, September 4 and 5; but in baseball, “September” means Labor Day and beyond). Since then, the actions on the field have often seemed to exist on two planes simultaneously, the real-time present and the imagined future in which they will be played back with the force of memory.

It’s more than just a trick of our minds. There is also the fact that in September the Cubs have played some great, even brilliant games that–had they been played in October–would rank among the most exciting championship contests in years. (It’s as if the Cubs and their observers all shifted together into the next gear.) A half-dozen of them have been so enjoyably balanced, so exemplary of what the sport can provide, that it’s been an easy jump from microball to macroball–from following the individual game to conjecturing the overriding Game– between pitches.

Last Saturday, for instance. Three days after manager Zimmer sits down with his pitchers and catchers to discuss giving up nine runs to the last-place Phillies. Two days after Greg Maddux responds by restraining those same Phillies to one run. One day after winning a close one against the Pirates– the hottest team in the division, the only team to go better than .500 with the Cubs all month. Now the hero’s chair beckons Paul Kilgus, wearing his team-worst 4.63 ERA like a thorny mantle.

But Kilgus’s rejuvenated sinkerball, which was dead in mid-season, allows the Pirates only five hits, and two of them are kept in the ballpark by the stiff cold wind. (It’s a team Game that depends on individual efforts.) Another un-likely hero is the newly acquired Marvell Wynne: unlikely because he starts out as the goat, misplaying a wind-whipped fly ball into a run-scoring triple in the first inning, before tripling himself in the third, driving in the Cubs’ first run and soon scoring the next. (The Game offers endless opportunities to atone for mistakes.) And then, so as to extract the maximum drama while considerately allowing the chilled crowd to leave at a reasonable time, the Cubs effortlessly manufacture the winning run in the bottom of the ninth, this time off the bat of Mitch Webster, the forgotten outfielder. (The beauty of the Game lies in the inherently fair structure; the clock never runs out, each team gets the same number of innings, and each inning allows the discrete chance to win the game.)

Each series this month has yielded such moments, and one would be hard pressed to name a turning point. The sweep of the Expos, which effectively punctured their most fantastic remaining hopes? The above-mentioned Kilgus performance, the fulcrum game on which turned last weekend’s sweep of the Pirates? Or (as I suppose most people will suggest) the weekend of September 8, when the Cardinals brought their legions of red-clad supporters to Chicago, turning the ballpark into a college football stadium, with each team’s scores wringing equal cheers and chants from the crowd–only to watch the Cubs take two of three?

The first of those games was the grand debacle in which the Chicagos blew a six-run lead and the Cards crept to within a half-game of first. That the Cubs would then proceed to win the next five was not surprising for this, the streakiest championship contender in modern memory; that they would win those games by routinely allowing their opposition two runs or less is nothing short of remarkable, given that the pitching had been disarrayed for weeks. Somehow, like a Scout troop stumbling off an amusement-park whirligig, the pitchers suddenly righted themselves, cleared their senses, and returned to normal functioning.

Coming back, and coming from behind–as they did September 9, the day after the blowout–might have been the most telling game of this summer. But let me dwell instead on the next day’s gem: the rubber game, the game that pushed the Cardinals down one more rung and sent them careening into a six-game losing streak. This was the game in which Zimmer suddenly decided to send Steve Wilson to the mound, saving the scheduled starter Greg Maddux for the following night’s game against Montreal. So Wilson (whose own pitching has mirrored the Cubs’ streakiness) struck out ten in the five innings he worked. The next three pitchers struck out another eight Cardinal batters for a total of 18 Ks by four pitchers–an accomplishment in my mind far greater than 18 Ks by one pitcher, since it requires not one but several arms to be operating at their peaks.

And when the Cardinals weren’t striking out, the Cubs defense was doing most of the right things. When the scary speedster Vince Coleman opened the visitors’ third with a clean single, everyone knew he’d be bolting for second–which he stole easily. But few expected that on the very next pitch he’d bolt for third–or that the Cubs catcher, Joe Girardi, would be ready to throw him out, giving hubris its comeuppance. The Cubs reached back for a textbook double play in the eighth, the pitchers walked only three, and the Cards’ lone run scored as a result of Wilson’s fourth-inning balk–the brilliant outing flawed (but not seriously) by a moment of carelessness. And the Cubs batters, in the trademark style of the 1989 season, waited until the game’s second half to score two on a homer, then single runs in the eighth and ninth. Great pitching to blunt a pesky offense. The efficient economy of disciplined batters alert to the moment’s needs. The sky was a coffee-table-book blue, the clouds seemed painted, and the oversold stadium seemed to sway in time to the pitchers’ rhythms.

What a game. What a Game.