New York's positivity rate had hovered around 1% for weeks, a hard-won metric after the state tallied thousands of cases per day during the peak of its outbreak in the spring. The rate's uptick now comes as 27 other states recorded increases in the number of cases for two straight weeks.
"It's basically Brooklyn, Orange and Rockland that are increasing this number," Cuomo told reporters on Monday, adding that state health officials were looking into COVID-19 clusters in these locations. He said health officials were still trying to find a reason for the rise in those areas, all of them in the southern part of the state.
In some Brooklyn neighborhoods, the positivity rate is as high as 5-7%, the city health department said on Monday.
Cases in New York state have risen 4.4% so far in September, one of the smallest increases among US states, according to a Reuters tally. The state's positive test rate remains much lower than that of some Midwestern states, where 15% of tests have been coming back positive.
Cuomo urged New Yorkers to remain vigilant in mask-wearing and warned of consequences if they do not.
"It's not time to get tired because the virus isn't tired," he said.
The number of new cases has risen for two weeks in a row in 27 out of 50 US states, with North Carolina and New Mexico both reporting increases above 50% last week, according to a Reuters analysis.
The Midwest has emerged as the country's new hotspot, with hospitalizations surging in some states.
Wisconsin set records for new cases twice last week and is now reporting more new infections each day than Florida. South Dakota, Utah and Wyoming have all set records for new daily cases three times this month.
The positivity rate has risen to 26% in South Dakota, up from 17% last week, according to an analysis using testing data from The COVID Tracking Project, a volunteer-run effort to track the outbreak. According to the analysis, on Monday, Wisconsin's rate was 19%, Iowa's was 16%, Missouri's was 16%, Kansas' was 15% and Nebraska's 14%.
The World Health Organization considers rates above 5% concerning because it suggests there are more cases in the community that have not yet been uncovered.
US top infectious disease expert Anthony Fauci told ABC's Good Morning America on Monday that he was concerned about the trend as the weather gets colder and people spend more time indoors, increasing the likelihood of spread.
"We're not in a good place ... because as we get into the fall and the winter you really want the level of community spread to be as low as you can possibly get it," Fauci said.
The United States is reporting 45,000 new infections on average each day, compared with 40,000 a week ago and 35,000 two weeks ago.
Cities and states have continued reopening at varying speeds. Chicago Mayor Lori Lightfoot on Monday said she would loosen capacity restrictions related to COVID-19 for bars, restaurants and health clubs later this week.
"This next step in our reopening is good news for business owners as well as the communities they serve and the thousands of residents that work for them," Lightfoot said in a statement.
On Friday, Florida Governor Ron DeSantis lifted all capacity restrictions on bars and restaurants. Video footage posted to social media over the weekend showed mask-less Floridians drinking and dancing in crowded bars.
The state had recorded over 690,000 cases of the virus as of Monday, according to its health department website.