This is part of a new series looking at pressing coronavirus questions of the week. We'd like to hear what you're curious about. Email us at [email protected] with the subject line: "Weekly Coronavirus Questions."

The global spread of COVID-19 cases continues, with cases now in at least 115 countries. Authorities in the U.S. and other countries are banning large gatherings, encouraging social distancing, and urging frequent hand washing.

The virus is quickly reshaping lives, economies and health care systems, and new questions keep arising.

Each week, we'll answer some of the pressing questions are on people's minds about coronavirus and what it means for everyday life. Send us your questions at [email protected].

I have an international trip scheduled. Should I cancel it?

Things are changing rapidly when it comes to travel. Organizations that issue travel advisories like the State Department and the Centers for Disease Control and Prevention are ramping up their warnings.

The U.S. State Department released a Global Level 3 Health Advisory on Wednesday that suggests U.S. citizens reconsider traveling abroad — regardless of the destination.

The advisory warns that with many areas around the world experiencing outbreaks, localities are "taking action that may limit traveler mobility, including quarantines and border restrictions. Even countries, jurisdictions, or areas where cases have not been reported may restrict travel without notice."

So if you travel abroad, you could potentially find yourself in quarantine or have a hard time getting home.

Additionally, President Trump has announced that he is banning travel from Europe beginning Friday at midnight. On Saturday he announced he's extending restrictions on travel from the United Kingdom and Ireland, as well.

U.S. citizens and legal permanent residents will be permitted to return to the U.S. from Europe, but they will be screened and could face quarantine if they show symptoms of COVID-19, the disease caused by the coronavirus. Many airlines are slashing flights due to the ban, causing further snarls.

For those at higher risk of getting sick from COVID-19 — including older people and those with other medical conditions — the Centers for Disease Control and Prevention advises avoiding cruise ships and unnecessary plane travel. The CDC also suggests that travelers in general defer cruises for now.

Kenzo Tribouillard / AFP via Getty Images

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AFP via Getty Images

What's this talk about "flattening the curve"?

You may have noticed many people are suddenly talking about the need to "flatten the curve."

That conversation refers to a specific graph that shows the number of COVID-19 cases over time.

The curve seen in red shows the sharp spike in cases that could occur if we don't take preventive measures. In that scenario, a huge volume of cases overwhelms the health-care system, and there aren't enough hospital beds and respirators for those who need them.

The second curve, in blue, shows what's to be expected if we do take preventive measures: the number of cases is lower and is spread out over a longer period. That flatter curve is the goal right now in many places that are already seeing a lot of cases of COVID-19.

A huge benefit of slowing the spread of coronavirus is that more people who get severe cases will be able to get the health care they need to stay alive. In the words of public health expert Drew Harris, who made the original version of the chart: "It's the difference between finding an ICU bed & ventilator or being treated in the parking lot tent."

Even if the virus is one that many people catch eventually, as some have warned, flattening the curve gives health-care systems more time to build capacity, develop treatments and eventually a vaccine.

How long does the new coronavirus live on surfaces?

The World Health Organization says that studies suggest coronaviruses may persist on surfaces for a few hours or up to several days. How long COVID-19 lasts can depend on different conditions, including the type of surface, the temperature and humidity.

New research published Wednesday found that the virus can live up to three hours in the air, up to four hours on copper, up to 24 hours on cardboard and up to two or three days on plastic and stainless steel.

The study was conducted by government scientists and researchers at Princeton and UCLA; it has not yet been peer-reviewed. And the study doesn't show how often the virus is actually transmitted this way.

The CDC says that it may be possible for someone to get COVID-19 by touching a surface or object that has the virus on it and then touching their mouth, nose, or possibly their eyes.

But, the CDC says, the most common way for the virus to spread is through respiratory droplets if an infected person coughs or sneezes close to you. These droplets can land in the mouths or noses of people who are nearby or possibly be inhaled into the lungs.

Should I use something other than my hand to turn off the water after I wash my hands with soap and water?

There isn't enough data to prove that you can pick up many germs by turning off a faucet with your bare hands after washing up. But doctors and health specialists who spend a lot of time thinking about infection recommend using a paper towel or your elbow in case there are germs on the faucet that could infect your newly clean hands.

Faucets are "worry spots in terms of areas that could be contaminated in restrooms," says Dr. Mark Gendreau, chief medical officer at Beverly Hospital in Massachusetts.

That perspective is shared by Tania Busch Isaksen, a lecturer at the University of Washington's department of Environmental and occupational health sciences: "You just turned that [faucet] on when they were dirty, so now you're recontaminating your hand."

We'll answer more questions next Friday. If you've got one, sent it to [email protected] by Wednesday, March 18, with the subject line "Weekly Coronavirus Questions."

NPR's Pien Huang and Elena Renken contributed to this report.

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