A pandemic of the novel coronavirus has now killed more than 738,000 people worldwide.
Over 20 million people across the globe have been diagnosed with COVID-19, the disease caused by the new respiratory virus, according to data compiled by the Center for Systems Science and Engineering at Johns Hopkins University. The actual numbers are believed to be much higher due to testing shortages, many unreported cases and suspicions that some national governments are hiding or downplaying the scope of their outbreaks.
Since the first cases were detected in China in December, the United States has become the worst-affected country, with more than 5 million diagnosed cases and at least 164,502 deaths.
Here's how the news developed on Tuesday. All times Eastern.
9:53 p.m.: Gov't partners with Moderna to produce 100M vaccine doses
The U.S. Department of Health and Human Services (HHS) and Department of Defense announced that they have made an agreement with Moderna to manufacture and deliver 100 million doses of the company’s COVID-19 vaccine candidate.
Under the deal, worth up to $1.525 billion, Moderna will manufacture the vaccine doses while clinical trials are underway. The federal government will own the vaccine doses. If authorized by the FDA and used in a COVID-19 vaccination campaign, they will be available to Americans at no cost, though health care professionals could charge for administering them.
As part of the deal, the U.S. government has the option to purchase up to an 400 million additional doses. Moderna is developing the vaccine, which began its Phase 3 clinical trial on July 27, in collaboration with the government.
"Never before has a vaccine in the developed world have gone from Phase 1 to Phase 3 as quickly as the Moderna vaccine," HHS Secretary Alex Azar said in a call with reporters Tuesday night.
The Trump administration has similar agreements in place with five other vaccine developers: Pfizer, Novavax, Oxford/AstraZeneca, Johnson & Johnson, and Sanofi and GlaxoSmithKline.
6:47 p.m.: CDC issues guidance on dealing with 'mask bullying'
The CDC has released new guidance for K-12 schools on face masks, including having a plan in place to address bullying and angry parents.
"Stigma, discrimination, or bullying may arise due to wearing or not wearing a cloth face covering," the CDC states. "Schools should have a plan to prevent and address harmful or inappropriate behavior."
The CDC also notes that since not all families may agree with mask policies, "schools should have a plan to address challenges that may arise and refer parents, caregivers, and guardians to CDC's guidance on cloth face coverings."
The CDC recommends that people ages 2 and up who do not have trouble breathing should wear cloth face coverings in public settings and when around those outside their household, as part of mitigation measures to help slow the spread of COVID-19.
In its new school guidance, the CDC also suggests that schools remind parents and staff to avoid touching the outside of the mask, and to wash their hands after they do. It also recommends adding cloth face coverings to "back to school" shopping lists.
4:30 p.m.: Pac-12, Big Ten postpone all sports including football
The Pac-12 Conference is postponing all sports through the end of 2020 due to the pandemic.
"Unlike professional sports, college sports cannot operate in a bubble," Pac-12 Commissioner Larry Scott said in a statement. "Our athletic programs are a part of broader campuses in communities where in many cases the prevalence of COVID-19 is significant. We will continue to monitor the situation and when conditions change we will be ready to explore all options to play the impacted sports in the new calendar year."
The Big Ten Conference said earlier Tuesday that it too is postponing the football season as well as all other fall sports.
"As time progressed and after hours of discussion with our Big Ten Task Force for Emerging Infectious Diseases and the Big Ten Sports Medicine Committee, it became abundantly clear that there was too much uncertainty regarding potential medical risks to allow our student-athletes to compete," Big Ten Commissioner Kevin Warren said in a statement.
4:20 p.m.: Over 800 students quarantined in Georgia school district
Georgia's Cherokee County school district has ordered 826 students and 42 teachers to quarantine due to possible exposure in the six days schools have been open, The Atlanta Journal Constitution reported.
Of the more than 42,000 students in the district, about 25% of them chose to do virtual learning, according to the outlet.
One high school in the district has announced that it will close through at least Aug. 30 following 14 confirmed cases. Remote learning for those students will begin Thursday.
Cherokee district staff must wear masks but students do not, the outlet said.
Cherokee County is about 40 miles north of Atlanta.
11:45 a.m.: Florida sees new record daily death toll
Hard-hit Florida reached a new record daily death toll with 276 additional fatalities reported on Monday, according to the state's Department of Health.
The previous high record was 257 deaths reported on July 31.
Florida, with more than 542,000 diagnosed coronavirus cases, has the second highest number of cases in the U.S. behind California.
At least 8,684 people in Florida have died, according to the state's Department of Health.
11:25 a.m.: Hawaii, South Dakota, Virgin Islands added to NY, NJ, CT travel list
Hawaii, South Dakota and the Virgin Islands have been added to New York, New Jersey and Connecticut's travel advisory list, New York Gov. Andrew Cuomo announced Tuesday.
Alaska, New Mexico, Ohio and Rhode Island have been removed from the list.
Those traveling to New York, New Jersey or Connecticut from states on the list must quarantine for two weeks when arriving.
A state or territory is added to the list if it has a positive test rate higher than 10 per 100,000 residents over a one-week average or a 10% or higher positivity rate over a one-week average.
Here are the states and territories currently on New York's travel advisory list: Alabama, Arkansas, Arizona, California, Florida, Georgia, Hawaii, Iowa, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Minnesota, Missouri, Mississippi, Montana, North Carolina, North Dakota, Nebraska, Nevada, Oklahoma, Puerto Rico, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, Virgin Islands and Wisconsin.
In New York state, once the U.S. epicenter of the pandemic, .86% of those tested on Monday were positive, Cuomo said.
10:40 a.m.: UMass cancels football season
The University of Massachusetts is canceling its football season, athletic director Ryan Bamford announced Tuesday.
"The continuing challenges surrounding the COVID-19 pandemic posed too great of a risk," he said in a statement.
Football players started returning to campus in June. In the last seven weeks, there has been one positive coronavirus test among the more than 600 tests administered to the team, the school said.
7:29 a.m.: 'The point is not to be 1st with a vaccine,' Azar says
U.S. Health and Human Services Secretary Alex Azar said "transparent data" from phase three clinical trials is necessary to determine whether a vaccine is actually safe and effective.
Azar made the comments during an interview Tuesday on ABC News' "Good Morning America" following news that Russia had become the first country in the world to officially register a COVID-19 vaccine and declare it ready for use. Moscow approved the vaccine before completing its final Phase III trial, and no scientific data has been released from the early trials so far.
"The point is not to be first with a vaccine; the point is to have a vaccine that is safe and effective for the American people and the people of the world," Azar said on "GMA."
The U.S.-led Operation Warp Speed initiative, which the Trump administration introduced in early April, currently has six vaccines in development, including two that are in Phase III trials -- the final stage before a vaccine candidate could potentially be authorized for use by the Food and Drug Administration. Azar said he believes the United States "could have FDA-authorized or approved vaccines by December."
"We believe that we are on track towards having tens of millions of doses by December of FDA gold-standard vaccine, and hundreds of millions of doses as we go into the new year," Azar said. "It will really depend on the speed at which the clinical trials enroll and people are vaccinated and then are exposed to the virus."
6:31 a.m.: New Zealand returns to lockdown after finding local transmission
New Zealand Prime Minister Jacinda Ardern announced Tuesday that the city of Auckland would temporarily return to lockdown, after four new locally-transmitted cases of COVID-19 were identified in a household in the region.
New Zealand had gone 102 days without recording any locally-transmitted cases -- until now.
Auckland will be placed under level three restrictions for three days, starting Wednesday afternoon. The rest of the country will go into level two until midnight on Friday.
Residents of Auckland will be asked to stay home where possible, while restaurants, bars and non-essential shops will shutter. Schools across the city will also be closed for those three days and gatherings of over 10 people will be prohibited.
"We're asking people in Auckland to stay home to stop the spread," Ardern said at a press conference Tuesday. "Act as if you have COVID, and as though people around you have COVID."
What to know about coronavirus:
- How it started and how to protect yourself: Coronavirus explained
- What to do if you have symptoms: Coronavirus symptoms
- Tracking the spread in the U.S. and worldwide: Coronavirus map
5:10 a.m.: Russia becomes 1st country to approve COVID-19 vaccine, Putin says
Russian President Vladimir Putin announced Tuesday that his country has become the first in the world to grant regulatory approval to a COVID-19 vaccine.
Speaking at a meeting with his cabinet ministers on state television, Putin said the vaccine had "passed all the needed checks" and had even been given to one of his daughters. The vaccine will soon be administered to Russian health workers, he said.
The vaccine, developed by the state-run Gamaleya Research Institute of Epidemiology and Microbiology in Moscow, was officially registered and declared ready for use after less than two months of human testing, without completing its final Phase III trial. So far, the drug has been tested on fewer than 100 people and Russia has yet to release any scientific data from those early trials.
The U.S. Centers for Disease Control and Prevention says Phase III trials must involve a minimum of 3,000 volunteers to be recognized.
Dozens of COVID-19 vaccine candidates are being developed by teams of researchers around the world, and several are in final Phase III human trials, according to the latest data from the World Health Organization.
3:45 a.m.: US records under 50,000 new cases for 2nd straight day
There were 49,544 new cases of COVID-19 identified in the United States on Monday, according to a count kept by Johns Hopkins University.
It's the second consecutive day that the nation has recorded under 50,000 new cases. An additional 525 coronavirus-related deaths were also reported.
Monday's caseload is well below the record set on July 16, when more than 77,000 new cases were identified in a 24-hour reporting period.
A total of 5,094,565 people in the U.S. have been diagnosed with COVID-19 since the pandemic began, and at least 163,465 of them have died, according to Johns Hopkins. The cases include people from all 50 U.S. states, Washington, D.C. and other U.S. territories as well as repatriated citizens.
By May 20, all U.S. states had begun lifting stay-at-home orders and other restrictions put in place to curb the spread of the novel coronavirus. The day-to-day increase in the country's cases then hovered around 20,000 for a couple of weeks before shooting back up and crossing 70,000 for the first time in mid-July.
Many states have seen a rise in infections in recent weeks, with some -- including Arizona, California and Florida -- reporting daily records. However, the nationwide number of new cases and deaths have both decreased in the last week, according to an internal memo from the Federal Emergency Management Agency obtained by ABC News Monday night.
ABC News' Brandon Baur, Anne Flaherty, Whitney Lloyd, Josh Margolin, Patrick Reevell and Scott Withers contributed to this report.