(CNN) The United States may not see a "double whammy" this fall of both the coronavirus and influenza, Dr. Anthony Fauci said Thursday.
The director of the National Institute of Allergy and Infectious Diseases pointed to the Southern Hemisphere, where it's late winter.
Australia has experienced an almost non-existent flu season, Fauci said in an interview with radio station WTOP. The country has had the fewest number of flu cases in memory, he said.
Fauci said he doesn't want Americans to get complacent, and he urged people to get a flu shot, wear masks, avoid crowds, keep physically distanced and wash their hands frequently.
"It is entirely possible that, despite the fear that we were going to have a double whammy, namely flu season superimposed upon a continuation of Covid-19, that may not be the case," Fauci said.
While it's impossible to say what's going to happen when flu season gets underway in the US this fall and winter, a new study suggests that measures like social distancing, teleworking and school closures that slow the spread of the novel coronavirus could also lead to a mild flu season this year.
"If extensive community mitigation measures continue throughout the fall, influenza activity in the United States might remain low and the season might be blunted or delayed," the researchers wrote in the study, published Thursday in the Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.
Flu virus circulation declined dramatically within two weeks after US officials declared a national emergency in mid-March, researchers said. They also noted that the summer circulation of the flu is "currently at historical lows."
This will be the most important flu season in the country's history, said US Surgeon General Dr. Jerome Adams.
A surge in flu and Covid-19 cases at once could overwhelm health care system capacity, Adams said at an event hosted by the U.S. Chamber of Commerce Foundation.
Adams said the flu season will provide an opportunity to instill vaccine education and confidence in communities.
"We need to understand that, number one, the biggest predictor of who's going to get the Covid vaccine is going to be, I think, who gets the flu vaccine," Adams said. "It's an opportunity to prime the pump and have that conversation."
Adams said that flu symptoms are similar to Covid-19 symptoms, making it hard to tell the two apart.
If too few Americans get a Covid-19 vaccine when it becomes available, it won't help reduce the spread of the deadly virus, Fauci said.
In an interview with The Wall Street Journal, Fauci addressed the risks if not enough people take the vaccine.
Even a third of Americans getting vaccinated against the coronavirus won't be enough, he said.
"It's a combination of how effective a vaccine is and how many people use it," Fauci said. "If you have a vaccine that is highly effective and not enough people get vaccinated, you're not going to realize the full, important effect of having a vaccine."
The less protective a vaccine is, the more people need to get it to provide population-wide immunity, Fauci said. The fundamental goal is to get the level of infection so low that when there are little outbreaks, they're easy to control, he said.
A recent poll from the Kaiser Family Foundation found that 54% of respondents said they would not get the vaccine if it was available for free before the November 3 presidential election -- a time frame suggested by President Donald Trump but one health officials say is unlikely.
Separately, the Pew Research Center found that only 51% of Americans surveyed said they would get a Covid-19 vaccine if it were available today -- down from 72% in May. The survey found 77% thought it was "very or somewhat likely" that a vaccine would be approved before its safety or effectiveness is fully understood, and 78% said they were concerned vaccine approval will move too fast.
Most, 76%, said they were concerned about the side effects and said that was the main reason they would "definitely or probably not" get a vaccine.
The hesitancy of many people to get a Covid-19 vaccine when it becomes available is an issue that needs to be urgently addressed, said Dr. Francis Collins, director of the National Institutes of Health.
"Those who are vaccine hesitant have had their hesitancy enhanced by a variety of things that are happening right now, particularly the unfortunate mix of science and politics," Collins said at an event hosted by the National Academies of Sciences, Engineering and Medicine. "I don't want to have us, a year from now, having a conversation about how we have in our hands the solution to the worst pandemic of more than 100 years, but we haven't been able to actually convince people to take charge of it," Collins said.
Fauci said he still thinks it will be the final months of the year before a vaccine is proven to be safe and effective. ''I would still put my money on November/December," Fauci said during a Congressional Hispanic Caucus Institute panel on global pandemics.
According to data from Johns Hopkins University, there have been more than 6.6 million cases of coronavirus reported in the United States. More than 197,000 people have died.
A wedding in Maine is linked to 176 Covid-19 cases and the deaths of seven people who didn't attend the celebration, highlighting how easily and quickly coronavirus can spread at social gatherings, public health experts say.
For months, doctors have stressed the importance of wearing masks, social distancing, and avoiding large gatherings.
But outbreaks have stemmed from Memorial Day events, Fourth of July celebrations and a massive motorcycle rally in Sturgis, South Dakota.
The wedding in Millinocket on August 7 had about 65 guests, a violation of the state's 50-person limit for indoor events, the Maine Center for Disease Control and Prevention said.
The event is linked to outbreaks that have unfolded at a nursing home and a jail, both more than 100 miles away from the wedding venue, among people who had only secondary or tertiary contact with an attendee.
Residents at Maplecrest Rehabilitation and Living Center accounted for 39 cases tied to the wedding and six of the seven deaths thus far, Maine CDC Director Dr. Nirav D. Shah said.
"The virus favors gatherings," Shah added. "It does not distinguish between happy events like a wedding celebration, or sad farewells, like a funeral."