Boston Mayor Marty Walsh on Sunday declared a public health emergency over the coronavirus outbreak and announced sweeping changes for bars and restaurants in the city in an effort to protect residents.

The emergency declaration will help the city marshal resources, Walsh said Sunday at a news conference at City Hall. The regulations for the city's eateries come after a slew of South Boston restaurants and bars agreed to close Sunday after people had been seen packing them Saturday.

Walsh also strongly urged the city's residents to maintain social distancing, the practice of interacting as little as possible with others to be less likely to spread the new coronavirus, which has already killed more than 60 people in the United States and thousands abroad.

"Social distancing is not a vague, wishful strategy. It's backed by science," the mayor said, adding later, "it will save lives."

At a news conference Sunday, Walsh issued an urgent plea for residents to engage in social distancing amid the coronavirus outbreak.

Following up on his announcement Friday that Boston Public School buildings would be closed starting Tuesday, Walsh said that two school campuses will not open Monday, either, due to possible exposure in their communities: the Eliot and McKinley schools.

He acknowledged the hardship that families will face with schools closing and said that, among the ways it would help, the city will distribute food through set locations in the city's neighborhoods.

Boston Mayor Marty Walsh announced that the city's public schools will close Tuesday, March 17, for over a month in an effort to keep students, their families and staff safe during the coronavirus outbreak.

The changes for the city's bars, restaurants and clubs going forward are extensive, including:

They will have to cut their capacity in half by removing tables and chairs, to encourage social distancing.

No lines will be allowed to form outside.

Closing by 11 p.m., except eateries offering drive-thru, take out or delivery.

Any eatery that wasn't allowed to let food be carried out can now do so -- "we are basically allowing every single establishment that serves food in the city of Boston to serve takeout," he said.

Beer gardens won't be allowed to open for the season until the crisis passes.

Walsh said violators will be closed for 30 days. He also explained that he wants people to still be able to get food during the time of increased social distancing, and doesn't want the city's service workers to suffer too greatly. Additionally, he thanked the 14 or more bars and restaurants that on Sunday agreed to close after Saturday's packed rooms.

These requirements will be in effect on Monday, March 16, only, after Governor Charlie Baker issued a superseding emergency order that prohibits on-premises consumption of food or drink at bars and restaurants beginning on Tuesday, March 17.

"The health and safety of each and every Boston resident is our first priority," Mayor Walsh said in a statement following Gov. Baker's "unprecedented" press conference. "At this point, we are undoubtedly experiencing a public health emergency in the City of Boston, and it is clear that we need to activate every tool at our disposal."

Earlier Sunday, Walsh gave advice on how best to accomplish social distancing.

Higher risk individuals should avoid large gatherings, limit time in public areas and do not congregate in groups. This includes older adults, anyone with underlying health conditions, anyone with weakened immune systems, and anyone who is pregnant. — Mayor Marty Walsh (@marty_walsh) March 15, 2020

Elsewhere Sunday in Massachusetts, Somerville Mayor Joseph Curtatone also declared a local state of emergency, which is in addition to Governor Charlie Baker’s order to close all bars and restaurants in the state to on-site table service through April 17; and all public and private schools through April 7.

All of these measures are intended to slow the spread of the disease by limiting interpersonal contact.

“We understand the devastating economic impact this may have on local residents and businesses,” said Mayor Curtatone. “We have more than 4,000 people working in the food service and accommodations industry in Somerville, so our community will be hit hard by these changes. We wish we could tell people that some semblance of normalcy could avoid the most dire consequences, but it was crucial for the Governor to take this step today. Unfortunately, the epidemiologists consulting with us are advising that social distancing is our only current defense against a mass contagion.”

City officials are working with state and federal legislators to provide economic aid to the workers, families, and small businesses impacted by these coronavirus-related closures.

Declaring a local state of emergency in Somerville creates a formal mechanism for the city to be reimbursed by the federal government for its emergency response to this crisis.

People arriving to U.S. airports from abroad Saturday night reported waiting hours in line for required medical screenings amid the coronavirus outbreak.