Coronavirus updates: Space Force's second in command tests positive

The PolicyLab at Children’s Hospital of Philadelphia released a coronavirus forecast Wednesday saying "all states except Hawaii will see increased case counts over the next four weeks with at least half expected to have substantial case growth."

"The researchers warn that the projected rate of growth of this fall wave could overwhelm contact tracing efforts and threaten the effectiveness of school safety plans, eventually necessitating many schools to revert to online learning, particularly for older students, until the surge has passed," PolicyLab said in a statement.

Researchers forecast a higher growth in the Northeast as temperatures continue to drop.

"Resurgence risk [is] growing more quickly than anticipated in the warmer climate zones of the southern U.S," PolicyLab said.

ABC News' Brian Hartman contributed to this report.

A Mount Sinai study published Wednesday in the journal "Science" found that most people who experienced mild-to-moderate COVID-19 symptoms have "a robust antibody response" that kills the virus and is "relatively stable for at least five months."

"While some reports have come out saying antibodies to this virus go away quickly, we have found just the opposite -- that more than 90 percent of people who were mildly or moderately ill produce an antibody response strong enough to neutralize the virus, and the response is maintained for many months," Florian Krammer, a senior author of the paper and a professor of vaccinology at the Icahn School of Medicine at Mount Sinai, said in a statement.

"Determining the duration and levels of antibody that protect us from reinfection" is "essential for effective vaccine development," Krammer added.

The study included data from 30,082 people.

French President Emmanuel Macron announced a partial lockdown on Wednesday.

Bars and restaurants will be closed and private and public gatherings will be prohibited nationwide.

Permission slips will be required for outings, but schools and various public institutions and factories will remain open.

The restrictions, which will be reviewed every 15 days, go into effect Thursday night and will last through at least Dec. 1.

Macron's announcement follows an alarming spike in deaths from the virus as in addition to record numbers of new cases across France.

"The virus is circulating in France at a speed that even the most pessimistic forecasts had not predicted," Macron said. "If we do not put the brakes on hard today our hospitals will be overwhelmed."

On Tuesday, France lost 527 lives to COVID-19, Macron said. As of Wednesday, the nation's positivity rate was 18.6%.

France's public health agency has confirmed over 1,198,000 cases and 35,541 deaths.

ABC News' Ibtissem Guenfoud and Christine Theodorou contributed to this report.

Major League Baseball criticized Justin Turner for returning to the field Tuesday night when his team won the World Series after the Dodgers' third baseman was removed from the game because he tested positive for COVID-19.

Turner was put into isolation, according to a statement from MLB, but he "chose to disregard the agreed-upon joint protocols and the instructions he was given regarding the safety and protection of others."

"Turner’s decision to leave isolation and enter the field was wrong and put everyone he came in contact with at risk," MLB said. "When MLB Security raised the matter of being on the field with Turner, he emphatically refused to comply."

The Commissioner’s Office is investigating.

The Dodgers were tested Tuesday night, and both the Rays and Dodgers were tested again Wednesday, MLB said, adding that the teams' "travel back to their home cities will be determined after being approved by the appropriate authorities."

The Dodgers said Wednesday that the team will wait to celebrate with the fans "until it is safe to do so."