Spring fever continues to pummel primetime, with most firstrun shows — even hits like “Modern Family” and “Glee,” in their returns — at or near season-low levels last week.

It also remains a challenging time for new series looking to establish themselves, though ABC launched “Don’t Trust the B in Apt. 23” to pretty good numbers thanks to its lead-in from “Modern Family,” which despite lower numbers was the week’s top scripted show among young adults.

The Alphabet also saw OK perfs from “Scandal” in its second week and “GCB” in its sixth, while CBS saw its cop show “NYC 22” open modestly and NBC’s new comedy “Best Friends Forever” looked weak in its second.

It’s been years since a scripted series launched in April went on to become a ratings hit, so the shows trying to establish an audience right now are certainly fighting an uphill battle.

One returning show that is thriving despite the distractions that accompany spring is HBO’s second-year drama “Game of Thrones,” which was cable’s top primetime scripted show last week in both young adults and total viewers.

Overall last week, Fox rode “American Idol” to a victory among young adults, with its 2.4 rating/7 share in adults 18-49 followed by CBS (2.1/6), ABC (1.8/5), NBC (1.7/5) and Univision (1.5/4), according to Nielsen estimates. Fox tied CBS for the lead in adults 25-54, while the Eye led easily in total viewers.

“Idol” claimed the week’s top spots on the 18-49 ranker with its performance show (5.0/14 in 18-49, 16.81m) and results seg (4.3/13, 15.81m). The Fox vet has been TV’s top-rated music contest for five straight weeks now, after lagging NBC’s “The Voice” in February.

“Glee” returned from a six-week break with solid numbers for this time of year (2.7/8, 6.76m), placing second in its Tuesday slot. The stronger lead-in also helped 9 p.m.’s “New Girl” (2.8/7, 5.23m) rise from its low of the previous week.

Top scores for CBS came from Monday comedy anchors “Two and a Half Men” (3.6/9, 10.40m) and “How I Met Your Mother” (3.5/11, 8.00m), with the latter one of only two scripted programs to do better than a 10 share among adults 18-49 last week. Also, “NCIS” (3.1/9, 17.66m) was the week’s No. 1 drama in 18-49, 25-54 and total viewers.

The net, which is considering an expansion of its Thursday comedy lineup next fall, tried a “Big Bang Theory” repeat Thursday at 9 and it narrowly led its half-hour (3.1/8 10.21m). And an hour later, “Person of Interest,” the net’s current Thursday 9 p.m. show, looked good in a repeat at 10 (1.8/5, 8.58m).

CBS preemed “NYC 22” to lackluster numbers on Sunday (1.5/4, 8.86m), though it did retain most of its “Good Wife” lead-in (1.8/5, 10.16m).

ABC welcomed back “Modern Family” (4.2/11, 10.35m) after three weeks of repeats, and the show emerged as the week’s No. 3 series in 18-49, and No. 1 among scripted shows. It helped launch “Don’t Trust the B in Apt. 23” to solid numbers (2.9/7, 6.91m), tying for 14th on the week in the demo.

Thursday newbie “Scandal” held steady in its second week (2.0/6, 7.28m), airing out of “Grey’s Anatomy” (2.9/8, 8.85m).

The net’s new take on “Titanic” sank, with Saturday’s three-hour segment doing a 3 share in 18-49 and Sunday’s hourlong conclusion doing a 2. On Sunday it led into “GCB” (1.5/4, 4.43m), which took a hit as a result.

NBC was paced by “The Voice” (4.0/11, 10.52m), the frame’s No. 4 show, and also saw improved numbers for the show’s Tuesday results seg (3.5/9, 9.00m). Also, “Celebrity Apprentice” was on the rise Sunday (2.2/6, 6.66m).

Otherwise, it was slow going for the Peacock, with “The Office” its top scripted skein (2.2/6, 4.39m).

HBO’s “Thrones” held steady (1.8/4, 3.77m), which was good enough to put it ahead of other scripted cable originals for the week, with BET’s “The Game” (1.2/3, 2.26m) and FX’s season finale of “Justified” (1.1/3, 2.66m) coming closest in 18-49.

Faring well in its second week was Lifetime’s “The Client List” (1.0/3, 2.85m), which built on its “Army Wives” lead-in (0.9/2, 2.91m) in all key demos. At AMC, “Mad Men” (2.69m) and “The Killing” (1.81m) were down a bit week to week.