The Centers for Disease Control and Prevention says flu cases are on the rise, along with a spike in emergency room visits.
The health agency released the data Friday despite the Trump administration's halt of nearly all scientific communication coming from federal health agencies.
The CDC did not report the information as it usually does in a weekly breakdown of flu activity called FluView but instead posted information to a section that focuses on respiratory illnesses in general.
It said the amount of acute respiratory illness causing people to seek healthcare remains high and that ER visits nationally are "very high for diagnosed influenza and moderate for RSV."
Influenza test positivity "increased to 25%" as of the week ending on Jan. 18, up from 18% the week before, while nationally, wastewater viral activity levels for influenza A are at high levels.
Dr. Aaron Glatt, chief of infectious diseases at Mount Sinai South Nassau in New York, told NBC the CDC data is vital "to see what additional resources we might need to bring in."
"One piece of data in a huge data stream is probably not the end of the world," Glatt added. "However, I am concerned if this continues. We do need to know: Are we going up, or are we going down?"