Fauci, the United States' top infectious diseases expert, told CNN that U.S. cases have not yet declined to a point that signifies the end of the initial wave.
Although there has been a gradual decline in cases since the peak in July, the national daily increase is still hovering around 40,000.
Fauci again warned that Americans will face challenges as COVID-19 joins the threat of influenza this winter.
"Rather than say, 'A second wave,' why don't we say, 'Are we prepared for the challenge of the fall and the winter?" he asked.
New data from Johns Hopkins University Friday showed 44,100 new cases on Thursday and about 900 deaths.
Since the start of the pandemic early this year, there have been 6.98 million cases and 202,800 deaths. The United States surpassed 200,000 deaths on Tuesday.
An updated outlook from researchers at the University of Washington on Thursday said a "winter surge" could increase the national death toll to 3,000 per day in late December and a total of 371,000 deaths by Jan. 1.
The university's Institute for Health Metrics and Evaluation projects that, based on "expectations of people's decreased vigilance in the fall and seasonality," there will be a "major winter surge."
The researchers said the death toll would be just 275,000 by January If 95% of the U.S. population complied with recommended mask usage. Presently, it's estimated at less than 50%.
An updated ensemble forecast by the Centers for Disease Control and Prevention projects between 214,000 and 226,000 deaths by the middle of October.
In Wisconsin, officials reported a record number of hospitalizations -- about 30% of which are in intensive care. The state also reported the second-highest daily rise in cases (2,400).
Wisconsin has set several records this month as students have returned to school.