Amid the coronavirus pandemic, conversation has turned to "shelter-in-place" orders after six San Francisco Bay-area counties put them into effect on Tuesday.

It was rumoured that New York would follow suit after mayor Bill de Blasio warned residents that an order may come this week.

However, governor Andrew Cuomo's office were swift to deny the claims, saying that "the emergency policies that have been issued are of statewide impact, and the governor is making every effort to coordinate these policies with our surrounding states.

"Any blanket quarantine or shelter in place policy would require state action and as the governor has said, there is no consideration of that for any locality at this time."

Mr de Blasio insisted that he had been misunderstood and told reporters that "some people interpreted it as like closing the bridges or closing the border, you know, this kind of thing. That's not what I meant. I meant a model that is all about only doing what's essential and staying home, otherwise, not doing a lot of the optional things that people are still doing in New York City."

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With 7m people currently under the order in California, everything you need to know about a shelter-in-place order is below.

What is a shelter-in-place order?

Yale University's guide to emergency management describes a shelter-in-place order as "finding a safe location indoors and staying there until you are given an "all clear" or told to evacuate. You may be asked to shelter in place because of an active shooter; tornado; or chemical, radiological, or other hazard."

Although coronavirus is not as immediate as an active shooter, the US government is attempting to stop the spread of the disease, so forcing residents to stay in doors is an evolution of social distancing.

In San Francisco's case, the order gives residents the opportunity to leave their residences for essential needs.

What counts as an essential need could vary from state to state, but the City and County of San Francisco say that "everyone else is required to stay home except to get food, care for a relative or friend, get necessary health care, or go to an essential job."

They add that "it is OK to go outside for walks or bike rides if you are not in a group," and that people should "stay at least 6 feet apart when leaving your home for essential activities."​​

Those who are elderly or have underlying health conditions have been advised to stay inside until 7 April when the order is scheduled to end.

How does it differ from a lockdown?

In a lockdown, citizens are still able to leave their house, but they are not allowed to leave the area that has been locked down.

What this means in practice varies from place to place, but all agree that large gatherings and the continued opening of pubs and restaurants are not permitted.

In Italy, residents in lockdown are allowed to leave their residence to go to work or for health reasons, but have a set curfew of 6pm.

Is an order to stay at home different?

An order to stay at home is theoretically different to a shelter-in-place order, because in the former residents are allowed to leave their residence for essential needs.

However, the way San Francisco have adopted the shelter-in-place order, there is effectively no difference.

On Friday night, Illinois governor JB Pritzker announced their would be a stay at home order put in place in the state.

The order is similar to San Francisco's and Chicago Mayor Lori Lightfoot said: "I want to say to be clear, this is not a lockdown, it's not martial law.

"There's absolutely no need to change your normal purchasing habits. Please, the grocery stores will remain open and stocked. So please be mindful of your neighbors and do not hoard. Remember, this is the new normal, for now."

In theory a stay at home order is different to a shelter-in-place, but officials seem to be using the terms interchangeably.