WASHINGTON – President Donald Trump announced Friday that he is making an emergency declaration to address the coronavirus pandemic. It's not the first time a president has used such a declaration to deal with a public health crisis, but it is rare.

Trump made the announcement days after the World Health Organization formally declared the coronavirus a pandemic and as his administration has wrestled with scrutiny over some aspects of its initial response to the outbreak.

The president declared emergencies under several different provisions of the law, which he said would not only free up nearly $50 billion in disaster money to fight the spread of the virus but also expand capacity at hospitals and reduce other health regulations that could slow action.

Here are some details about what the president declared:

Didn't Trump already declare an emergency back in January?

The Trump administration declared a "public health" emergency in late January. That designation, technically made by Health and Human Services Secretary Alex Azar, made it easier for states to redirect staff responding to the virus. The announcement was made in tandem with a quarantine order for U.S. citizens returning from hard-hit areas of China.

What the White House announced Friday is far more substantial, and rare.

Trump has been blasting his predecessor, President Barack Obama, for not declaring "an emergency" fast enough in response to the 2009 Swine flu outbreak. But Obama actually did declare a public health emergency early in that outbreak, when there were only 20 known cases in the U.S. He did not declare other emergencies until months later.

More:Trump declares coronavirus emergency, orders first quarantine in 50 years

How is this emergency declaration different?

First,Trump declared an emergency under the Stafford Act, the same 1988 law presidents use to declare disaster areas after storms and other natural disasters. That frees up billions of dollars in Federal Emergency Management Agency funds to confront the coronavirus. Trump said about $50 billion is available (other estimates, including one from the White House after the president spoke, have pegged the figure at closer to $40 billion).

"This pandemic has the potential to cause severe consequences for our country's national and economic security," the president wrote in a letter announcing the decision late Friday. "It is therefore critical that we deploy all powers and authorities available to the federal government to provide needed relief."

Trump also declared an emergency under the National Emergencies Act, which will allow the Department of Health and Human Services to modify or waive regulations for Medicare, Medicaid and other programs. Waiving those regulations would also bring about changes to the broader medical system.

The president said the changes would including making it easier to offer tele-health services, so that patients don't have to come to a doctor's office in person for some consultations, waiving certain licensing requirements so that doctors can provide care across state lines and waiving capacity limits for hospitals.

Has that ever been done for this kind of problem before?

Yes. The Stafford Act isn't limited to natural disasters.Presidents have relied on the Stafford Act to free up funding after terrorist attacks, including the Sept. 11, 2001, and 2013 Boston Marathon attacks. The act also has been used for public health crises. President Bill Clinton declared an emergency under the Stafford Act to free up money in response to the West Nile virus in 2000, for example. Those declarations allocated millions to New York and New Jersey.

In 2014, Obama issued an emergency declaration for a chemical spill in West Virginia. Two years later, Obama issued an emergency declaration during the Flint, Michigan, water contamination crisis.

The National Emergencies Act has been used for many different purposes, and the president's power to define an "emergency" under that law is broad.

Is this the same thing as Trump's border wall emergency?

Sort of. Trump used the 1976 National Emergencies Act to invoke provisions of law that let him transfer money from the Pentagon to wall construction. He did that unilaterally after Congress declined to give him additional funding for wall construction. While the biggest part of Friday's coronavirus announcement involved the Stafford Act, Trump also declared an emergency under the National Emergencies Act. National emergencies under this act are quite common. Dozens of those emergencies declared by presidents remain in effect, often to freeze assets and impose other sanctions on foreign governments.

More:National emergencies are common; declaring one for a border wall is not

Oh, yeah? Name one.

No problem. Trump alone has signed several emergencies into law. For instance, he signed an executive order in 2018 that gave him power to slap sanctions on any foreign country that interferes in a U.S. election. That action was taken after criticism that Trump did not do enough to confront Russian meddling in the 2016 presidential election.

What is the Stafford Act?

The Stafford Act allows the federal government to offer a wide range of aid to states, municipalities, hospitals and even individuals.

Americans may be eligible for “immediate direct and financial assistance” to help with “housing and other disaster related needs,” according to the Association of State and Territorial Health Officials.

When the Stafford Act is activated to deal with a pandemic, the federal government can begin providing direct emergency medical care to citizens throughout the country. This could include the establishment of temporary hospitals, for example, to ease the nation’s projected shortage of intensive care beds.

The government could also use the act to provide food, water, medicine and other supplies to Americans.

Public facilities where aid is being administered could be eligible for reimbursements, including hospitals, schools and custodial care facilities. Eligible facilities would get 75% of their costs reimbursed from the federal government and 25% from their respective states.

Contributing: Nathan Bomey