Top U.S. infectious disease expert Dr. Anthony Fauci said on Friday he disagreed with President Donald Trump's assessment the country has "rounded the corner" on the coronavirus pandemic, saying the statistics are disturbing.

Fauci, the outspoken director of the National Institutes of Allergy and Infectious Diseases, said the United States was starting the flu season with a high baseline of around 40,000 new COVID-19 cases a day and deaths are averaging around 1,000 daily.

Trump, who has admitted playing down the severity of the virus since it emerged early this presidential election year, said on Thursday he believed the United States was "rounding the corner" on the health crisis.

"I have to disagree with that, because, if you look at the thing that you just mentioned, the statistics ... they are disturbing," Fauci said on MSNBC.

"If you're talking about getting back to a degree of normality which resembles where we were prior to COVID, it's going to be well into 2021, maybe even towards the end of 2021," he said.

Fauci said he hoped the country did not see a spike in cases after the Labor Day weekend as it did after other long holiday weekends since May.

It was important to get those infection rates down before the autumn and winter seasons when people will be spending more time indoors. "You don't want to start off already with a baseline that's so high," Fauci said.

COVID-19 and flu collision

Concerns over a second wave triggered by the coming autumn seasonal flu have risen among people, while a latest study conducted by European researchers suggests that influenza, indeed, could more than double the spread of the coronavirus.

A COVID-19 patient, on average, could spread the virus to two other persons, but the transmission rate would double if the patient, in the meantime, had the flu, research shows.

Scientific communities vary on whether seasonal flu would have an impact on the coronavirus, with some believe flu patients with their provoked body immune response can partially protect them against the coronavirus.

However, others hold that it's hard for co-infected patients to fight back two different viruses at the same time, and probably would accelerate the virus transmission due to coughing and sneezing, symptoms that are commonly seen among flu patients.

After analyzing the data collected from a simulation model tracking the co-circulation of seasonal flu and COVID-19, researchers found influenza was associated with an average 2-2.5-fold population-level increase in COVID-19 virus transmission.

They also point that the decline of new cases after the first wave in spring was not only caused by lockdown and social distancing measures but also by the end of the flu season.

The study, published on Medrxiv.org on Wednesday, has yet been peer-reviewed.

There was related research conducted by Google and Cold Spring Harbor Laboratory in May, showing that flu infection could significantly increase the amount of a special protein in the human body, which helps the coronavirus to infect cells.

(With input from Reuters)