Coronavirus latest: Ohio reports highest number of cases since July
The governor urged residents to be vigilant as Labor Day approaches.
A pandemic of the novel coronavirus has now killed more than 852,000 people worldwide.
Over 25.5 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 criteria for diagnosis -- through clinical means or a lab test -- has varied from country-to-country. Still, 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 virus has rapidly spread to every continent except Antarctica.
The United States is the worst-affected country, with more than 6 million diagnosed cases and at least 184,270 deaths.
California has the most cases of any U.S. state, with more than 713,000 people diagnosed, according to Johns Hopkins data. California is followed by Texas and Florida, with over 633,000 cases and over 631,000 cases respectively.
Nearly 170 vaccine candidates for COVID-19 are being tracked by the World Health Organization, six of which are in crucial phase three trials.
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Schools in Greece to reopen Sept. 14
Schools in Greece will reopen on Sept. 14, the government announced Tuesday.
Masks will be mandated indoors. Students in third grade and younger will be taught how to wear their masks properly.
Greece has 10,317 COVID-19 cases and 266 deaths, according to Johns Hopkins University data.
"The pandemic's evolution is dynamic," Greek Education Minister Niki Kerameus told reporters in Athens on Tuesday, adding that measures will be adjusted as necessary on local, regional and national levels.
"We will not hesitate to adopt measures that are more austere depending on the progression of the pandemic," Kerameus said.
ABC News' Christine Theodorou contributed to this report.
Start of in-person school delayed in NYC
The start of in-person learning in New York City public schools has been delayed to Sept. 21, Mayor Bill de Blasio announced Tuesday.
The district's blended-learning plan was scheduled to begin on Sept. 10.
"Teachers who usually get two days of professional development at the beginning of the school year will now get nine," schools Chancellor Richard Carranza said. "We've heard from everyone in our schools that have said we need some more time."
In averting a strike authorization vote by the United Federation of Teachers later Tuesday, de Blasio agreed to delay the start of school to Sept. 16 for all-remote instruction. In-person learning, which is limited to a few days per week, will begin Sept. 21.
The mayor also announced expanded testing for teachers, a significant concession to the United Federation of Teachers.
ABC News' Aaron Katersky contributed to this report.
Alaska, Montana added to New York's travel advisory list
Alaska and Montana have been added to New York's travel advisory list, which requires people traveling to the Empire State from a high-coronavirus area to quarantine for two weeks, New York Gov. Andrew Cuomo announced Tuesday.
The states and territories currently on New York's list are: Alaska, Alabama, Arkansas, California, Florida, Georgia, Guam, Hawaii, Iowa, Idaho, Illinois, Indiana, Kansas, Kentucky, Louisiana, Minnesota, Missouri, Mississippi, Montana, North Carolina, North Dakota, Nebraska, Nevada, Oklahoma, Puerto Rico, South Carolina, South Dakota, Tennessee, Texas, Utah, Virginia, the U.S. Virgin Islands and Wisconsin.
The list applies to areas with a positive test rate higher than 10 per 100,000 residents over a one-week rolling average or areas with a 10% or higher positivity rate over a one-week rolling average.
New York was the U.S. epicenter of the pandemic in March and April, but of those tested across New York state on Monday, less than 1% were positive, Cuomo said.
New York currently has 109 coronavirus patients in ICUs -- the lowest number since March 15.
White House reinstating public tours
White House public tours will resume on Sept. 12, though the number of visitors will be limited to 18% of the usual capacity, according to a Tuesday statement from the first lady's office.
Tours will also be cut down to two days per week instead of five days per week.
Everyone ages 2 and older must wear a face covering and practice social distancing.
Hong Kong begins mass COVID-19 testing effort
The government of Hong Kong has launched a mass COVID-19 testing program that is free and voluntary.
The government said 141 testing sites were opened and around 126,000 people were tested on Tuesday.
Over 674,000 people have made online appointments to get tested, the government said.
Hong Kong -- which has a population around 7.5 million -- has 4,823 coronavirus cases as of Tuesday. Ninety people in Hong Kong have died.
ABC News' Christine Theodorou contributed to this report.