Without control over the community spread of the delta variant, the virus has "ample opportunity to mutate," so "you may sooner or later get another variant," Dr. Anthony Fauci told "Good Morning America."

Fauci warned that it's possible a new "variant might be in some respects worse than the already very difficult variant we're dealing with now, which is a major reason why you want to completely suppress the circulation of the virus in the community."

There are still about 93 million eligible Americans who have not gotten vaccinated.

Fauci added, "People who say, 'I don't want to get vaccinated because it's me and I'll worry about me, I'm not having any impact on anybody else,' that's just not the case."

-ABC News’ Cheyenne Haslett

There are 5,042 new positive COVID-19 cases in Tokyo as of Thursday, according to the city's coronavirus information website.

Of those cases, 135 are severe and one has resulted in death.

It's a new record for Tokyo and a 178% increase since last Thursday, as the highly contagious delta variant spreads rapidly across the globe.

Texas reported 15,558 new COVID-19 cases Wednesday, the highest one-day count since Feb. 3, according to state health records.

The state has seen a major jump in cases in the last month, brought on by the delta variant, according to officials.

The seven-day average of new daily cases has increased from about 1,500 on July 2 to nearly 10,000 on Aug. 3, according to state health data.

As of Wednesday, 62.58% of Texas residents 12 and older have received at least one shot, according to the state health department.

Hundreds of student and staff members from the Marion School District in Arkansas are now quarantined in only the second week of the school year, officials announced.

The state has a ban on school districts imposing a mask mandate.

On Tuesday, the district said 253 students would begin their two-week quarantine due to 15 cases that were reported in the schools. This came after 168 students were already quarantined last week.

"If all students and teachers had been wearing a mask appropriately- then today's 15 positive cases would be isolated- but there would be no resulting quarantines for anyone else," the district said in a statement.

Arkansas Gov. Asa Hutchinson told reporters Tuesday he regretted signing the bill that banned masks in schools and urged the state legislature to amend the law to give schools the option.

A federal judge ruled Sunday in favor of Norwegian Cruise Line and will allow the company to require proof of vaccination on cruises out of Florida despite a state law that bans cruise ships from enacting such an order.

Norwegian sued the state last month contending that the law prevented them "from safely and soundly resuming passenger cruise operations from Miami, Florida."

Florida's law threatens to fine companies $5,000 each time they ask a customer to provide proof that they've been vaccinated.

Florida has seen a surge in COVID-19 cases and hospitalizations in the last couple of weeks, with most cases affecting unvaccinated residents.

Judge Kathleen M. Williams wrote in her decision that Norwegian "has demonstrated that public health will be jeopardized if it is required to suspend its vaccination requirement," and the Florida Department of Health, "identifies no public benefit from the continued enforcement of the Statute Case."

Neither the cruise line nor the Florida Department of Health issued immediate statements about the ruling as of Sunday evening.

-ABC News' Sam Sweeney