(CNN) Coronavirus is "my worst nightmare," in some ways more than Ebola or HIV, Dr. Anthony Fauci said Tuesday.
"Ebola was scary, but Ebola would never be easily transmitted," Fauci, director of the National Institute of Allergy and Infectious Diseases, said. Ebola outbreaks are also always highly local.
"HIV, as important as it is, was drawn out and over an extended period of time," added Fauci, who was speaking via recorded video at the Biotechnology Innovation Organization International Convention. Many never felt threatened by the disease because it was always a threat "depending upon who you are, where you are, where you live."
In the past, when people would ask Fauci to describe a potential disease that he feared most, he said he would often describe it as something that was a brand new respiratory infection that likely jumped from an animal and had a very high degree of transmissibility.
The world has seen outbreaks that have at least some of those characteristics, he said, but Covid-19 had all of those characteristics combined.
"Now we have something that turned out to be my worst nightmare," Fauci said. "In the period of four months, it has devastated the world."
The pandemic has killed more than 111,700 people in the United States, and nearly 409,000 worldwide, according to Johns Hopkins University. Around the globe there have been more than 7 million people infected.
It was "unexpected how rapidly," it would spread, he said.
"It just took over the planet," Fauci added, "And it isn't over yet."
Fauci also said there is still a lot to learn about the long-term negative effects of Covid-19 infection on patients.
"The thing that we don't yet fully appreciate is what happens when you get infected and you get serious disease and you recover? What are the long-term durable negative effects of that infection?" Fauci said.
Fauci explained that because there's still not enough experience with the virus, scientists don't know what patients who have recovered will be like in six months.
"We don't know the extent of full recovery or partial recovery, so there's a lot we need to learn," he said.
Fauci also spoke about the fight to prevent the disease.
There will be "more than one winner" in the Covid-19 vaccine field, he said.
"We're going to need vaccines for the entire world -- billions and billions of doses," Fauci said.
Fauci praised the "unprecedented" rapid response of pharmaceutical companies in working toward a vaccine and therapeutics for coronavirus, saying it "even outpaced the public health response in some respect, which you usually see it opposite."
Fauci said he hopes the work that is being done to fight Covid-19 will bring in the future "a degree of capability and preparedness to respond even better than we've responded right now."
The doctor said he doesn't think imposing price controls on vaccines before they are developed works, and instead called for the government to work in "good faith" with pharmaceutical companies to develop treatments during public health emergencies.
Speaking about vaccine affordability, Fauci said, "I have a lot of experience over the years dealing with pharmaceutical companies in which we're trying to develop an intervention. And the one thing that is clear is that if you try to enforce things on a company that has multiple different opportunities to do different things, they'll walk away."
Fauci explained profit has to be considered when developing vaccines with the private sector. "As long as it isn't such an outrageous way that it completely makes something out of the realm of the people who really need it," he said.