This flu season is shaping up to be one of the worst in decades, according to the United States' top infectious disease doctor.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said while it's impossible to predict how the flu will play out, the season so far is on track to be as severe as the 2017-2018 flu season, which was the deadliest in more than four decades, according to the US Centers for Disease Control and Prevention.

"The initial indicators indicate this is not going to be a good season -- this is going to be a bad season," Fauci said.

So far this flu season, at least 2,900 people in the US are estimated to have died of the flu, according to data released Friday by the CDC. That's 800 more deaths than estimated the previous week.

Flu cases and hospitalizations because of the flu have also risen sharply since the season began in October. CDC estimates there have been at least 6.4 million flu illnesses and 55,000 hospitalizations.