There were four states at the highest level of influenza-like illness (ILI) activity for the week, more than any other week of the 2015-2016 flu season, according to the Centers for Disease Control and Prevention.

Arizona, Kentucky, New Jersey, and New Mexico, along with Puerto Rico, were all at level 10 on the CDC’s 1-10 scale of ILI activity for the week ending March 5, 2016. Other states in the “high” range were Arkansas, Illinois, Nevada, and North Carolina at level 9 and Alabama and Mississippi at level 8, the CDC reported.

The proportion of outpatient visits for ILI was 3.5% for the week, the highest of the season so far and well above the national baseline of 2.1%. In addition to the 10 states and Puerto Rico with ILI levels in the high range, there were 13 states in the “moderate” range (6 or 7 on the 1-10 scale) and 12 states in the “low” range (4 or 5), with a total of 44 states at level 2 or higher, data from the CDC’s Outpatient Influenza-like Illness Surveillance Network (ILINet) show.

Two flu-related pediatric deaths were reported during week 21 of the flu season, although both occurred earlier: one during the week ending Feb. 13 and one during the week ending Feb. 27. There have been a total of 20 pediatric deaths reported for the 2015-2016 season, with Florida (four deaths), California, (three), Arizona (two), and Nevada (two) the only states reporting more than one, the CDC report noted.

The continued rise in ILI activity is somewhat unusual. The only season out of the previous 10 with a peak later than the current one was 2011-2012, which peaked at only 2.4% on the week ending March 17, 2012. The earliest of the bunch came during the 2009-2010 season, which peaked at 7.7% during the week ending Oct. 24, 2009, according to ILINet data.