Los Angeles County officials on Friday announced that stay-at-home orders would be extended through May 15.

The decision comes a little more than a week before the initial order was set to expire on April 19, and as more than 8,400 in the county have tested positive for the novel coronavirus.

California has been one of the states hit the hardest by COVID-19, along with New York and Washington state, but recent numbers suggest social distancing and other measures have helped slow the spread and flatten the curve. Experts warn, however, that those measures must stay in place longer even as the number of people being admitted to the hospital for the virus has somewhat slowed.

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"If you were to reduce physical distancing to the pre-health officer order levels, virtually all individuals in Los Angeles County, 95.6 percent per the model, would be infected by the pandemic by Aug. 1, 2020," said Christina Ghaly, the county's director of health services. "That number is starkly reduced, down to about 30 percent, if we maintain the current levels of physical distancing."

County officials also announced an extension of all current closures, including beaches, parks and trails. Public health officials are also urging residents to avoid leaving their homes for groceries or medications and advising delivery when possible.

Officials in New York, Illinois, Michigan and Ohio have also signaled that their issued stay-at-home orders and closures of nonessential businesses could be in place well into May or June.

The decision by Los Angeles County comes as the Trump administration is aiming to reopen some parts of the country in May.

Treasury Secretary Steven Mnuchin Steven Terner MnuchinLawmakers fear voter backlash over failure to reach COVID-19 relief deal United Airlines, unions call for six-month extension of government aid House Democrats plan to unveil bill next week to avert shutdown MORE told CNBC on Thursday that he believes companies could reopen in May as long as Trump “feels comfortable with the medical issues.”