This is the first in 15 flu seasons in which 49 states (Hawaii was the exception) reported “widespread flu activity” in the same week for three weeks straight, the CDC reported. Puerto Rico also reported widespread flu in weeks two and three.

“The first [notable characteristic of this season] is that flu activity became widespread within almost all states and jurisdictions at the same time,” Dr. Dan Jernigan, director of the influenza division at the Centers for Disease Control and Prevention, said on a conference call Friday morning. “The second notable characteristic is that flu activity has now stayed at the same level at the national level for three weeks in a row with 49 states reporting widespread activity each week for three weeks.”

“We often see different parts of the country light up at different times, but for the past three weeks the entire country has been experiencing lots of flu all at the same time,” Jernigan continued.

#FluFactFriday: Did you know? Over the past 15 flu seasons, this is the 1st time all states in the entire continental U.S. have reported widespread #flu activity during the same week. https://t.co/ycVdIWwWhU pic.twitter.com/6aGtv16C3S

— CDC Flu (@CDCFlu) January 19, 2018

While flu rates in states like California, which has seen high rates of hospitalization, appear to be declining, the 2018 flu season may not have reached its peak yet.

“Hopefully we’re in the peak currently, since the data is a week behind, or that it peaks soon,” CDC spokeswoman Kristen Nordlund told CNN. “Regardless, there is a lot of flu activity happening across the country and likely many more weeks to come.”

This season, 6.6% of doctor visits and hospitalizations have been flu-related, according to the CDC’s FluView, the national baseline is 2.2%.

“This is the highest level of activity recorded since the 2009 pandemic, which peaked at 7.7%,” Jernigan said, referring to the 2009 swine flu outbreak.

The 204-2015 flu season peaked at 6% of doctor visits or hospitalizations being related to the flu. During that season, 710,000 Americans were hospitalized with the flu, and over 34 million Americans contracted the flu.

This season, the elderly along with baby boomers (ages 50-64) have been hit the hardest. Thus far, the flu is being blamed for the deaths of 37 children; 148 died from the flu in the 2014-2015 season.

Here is what you need to know about the 2018 flu season and how to protect yourself, your family, and your dog.