Dr. Anthony Fauci cautioned Americans that a 'difficult time' could overtake the U.S. come fall if the COVID-19 outbreak and flu season strike the country in tandem.
He also called for a 'universal wearing of masks' at schools because it could slow the virus' spread and mitigate infections.
Fauci, a White House coronavirus task force member, made the concerning revelation during ABC News' World News Tonight with anchor David Muir on Monday.
According to him, if Americans don't fully embrace donning masks and social distancing, they could be faced with dual outbreaks that could inundate the country.
In July, CDC director Dr. Robert Redfield admitted that the convergence of the COVID-19 pandemic and the annual influenza season could become 'one of the most difficult times that we've experienced in American public health.'
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Dr. Anthony Fauci (pictured) said on Monday that Americans could face a 'difficult time' if the COVID-19 pandemic and the flu season converge this fall
'I totally agree,' said Dr. Fauci on Monday, adding that the country's trajectory depends on its commitment to health guidelines.
'If we do not do the things in a uniform way...as we get into the winter and fall, with the likelihood we'd have a convergence, we'd have a convergence of two respiratory diseases,' said Fauci.
'We can have a very difficult time.'
Fauci dismissed the idea that the COVID-19 pandemic will simply disappear and said people need to engage with suggested health guidelines.
'I want to impress upon the American people in a way that's so clear: There are things that we can do that would get the level down,' he told World News Tonight.
'If we go into the fall and the winter with the same situation… we will have upticks of percent positive, and then you have the inevitable surging of infection.'
Fauci: 'If we go into the fall and the winter with the same situation… we will have upticks of percent positive, and then you have the inevitable surging of infection' Pictured: Elementary school students wait for classes to begin in Godley, Texas
He added that there is a way to avoid the convergence, 'but it’s not by wishful thinking.'
The CDC estimated that the flu caused between nine million and 45 million illnesses since 2010.
Similarly, the flu has resulted in as many as 810,000 hospitalizations, while 12,000 to 61,000 deaths are counted annually.
The presence of both outbreaks in the U.S., especially at a time when the coronavirus has no vaccine or cure, could be detrimental to the country.
Previously, Fauci said he hoped to see less than 10,000 cases daily in the U.S. by fall.
The Rev. Arturo Corral (center) gives communion individually, to maintain social distancing among congregants, during Mass celebrated outdoors at the historic Our Lady Queen of Angels Church
But the U.S. is recording 50,000 to 70,000 cases a day, the World Health Organization reports, with significant case spikes in hot spot states like California and Florida.
On Monday, the U.S. had amassed 5,094,338 confirmed infections and more than 163,000 deaths.
'The way human nature is acting out there, it doesn't seem likely [this goal will be met]. But that doesn't mean it can't be done,' said Fauci.
'I don't know how more forcefully I can make that plea to the American people. That we can open the country, we can get back to normality, if we do some simple things.'
But Fauci said he's optimistic that the U.S. can meld together in the upcoming weeks to make a real stride of conquering coronavirus.
'My message is one of cautious optimism and hope,' said Fauci. 'But I'm also very realistic to know that if we don't do it, we’re going to continue to have this up and down.'