The new coronavirus that began as a handful of infections in central China has rapidly become a worldwide pandemic, shutting down entire cities, threatening the health of thousands and testing the strength of the global economy.

More than 155,000 cases of the coronavirus have been confirmed worldwide across more than 100 countries and regions, and more than 5,800 people have died as of Saturday evening, according to data from Johns Hopkins University. At the same time, more than 72,000 people worldwide have recovered from the virus.

As the rate of new cases in China continues to decline, more and more cases are being confirmed across the globe, with clusters in Italy and Iran. In the U.S., the death toll is creeping upward as new cases are cropping up across dozens of states.

Months into the outbreak, there are still more questions than answers. Here’s what you need to know about COVID-19.

• FAQ with a doctor: Should I panic? What are best prevention steps?
• How to prepare for a quarantine:  The shopping list 
• Not true: A running list of all the myths surrounding coronavirus 

What are the symptoms of coronavirus?

Symptoms can range from mild to severe, and some people don’t have any symptoms at all. The most common symptoms resemble the flu and include fever, tiredness and dry cough. Some people also develop aches and pains, nasal congestion, runny nose, sore throat or diarrhea.

About 1 in 6 people becomes seriously ill and develops difficulty breathing, according to the World Health Organization. If you experience fever, cough and shortness of breath, call your doctor.

Symptoms may appear anywhere between two to 14 days after exposure, with the average patient seeing onset at around five days, according to the CDC.

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How many coronavirus cases are in the US?

There are more than 2,500 confirmed cases in the U.S., according to Johns Hopkins. Officials warn that many more people are likely infected. Of the confirmed cases, some are travel-related, some have spread person-to-person, and some were repatriated to the U.S. from Wuhan, China, and the Diamond Princess cruise ship.

Map of coronavirus cases in US

Cases have been reported in at least 48 states and the District of Columbia, according to the Johns Hopkins data dashboard.

How many people have died from the coronavirus in the US?

At least 51 people have died after contracting the coronavirus in the U.S.: 37 in Washington state, five in California, three in Florida and one each in Colorado, New Jersey, New York, South Dakota, Kansas and Georgia.

In Washington state, at least 23 of the patients died at EvergreenHealth Medical Center. At least 25 of the victims were associated with a nursing home in suburban Seattle, according to local health officials. At least one had previously been aboard the Diamond Princess cruise ship.

How many cases of coronavirus are there worldwide?

Here’s a breakdown of worldwide numbers, as of Saturday:

• More than 155,000 cases
• At least 5,800 people have died
• More than 72,000 people have recovered

Travel restrictions for US citizens

The U.S. State Department warned Americans to avoid traveling abroad and issued a global travel warning of level 3 — “reconsider travel,” one level below its strongest warning — for all overseas travel. It also advises U.S. citizens against traveling by cruise ship and against long airplane trips and crowded places.

The CDC has advised Americans to “avoid nonessential travel” to Europe — a Level 3, its highest warning. This covers essentially the entire continent — 29 countries and principalities — including some of the most popular destinations for U.S travelers, Germany, France, Spain and Italy.

The CDC also recommends avoiding all non-essential travel to China, South Korea and Iran. This does not include Hong Kong, Macau or Taiwan. Japan is at a level 2 alert (practice enhanced precautions), and Hong Kong is at a level one watch (practice usual precautions).

The U.S. suspended travel from Europe for 30 days starting Friday. The order suspends the entry of most foreign nationals who have been in 26 European countries at any point during the 14 days prior to their scheduled arrival to the United States. The United Kingdom and Ireland were initially excluded from the ban but have been added due to a spike in cases there.

Many people have canceled trips abroad amid fears of contracting the virus. Some universities have canceled study abroad programs, and some companies have put a pause on international travel.

Check out the latest travel advisories for US citizens

How to prepare for coronavirus

Take typical flu-season precautions: Avoid close contact with people who are sick. Don’t touch your eyes, nose and mouth. Cover your cough. Stay home when sick. Clean household objects and surfaces. Wash your hands for at least 20 seconds.

If you’re sick and want to prepare for a possible quarantine, here’s a shopping list of items you should consider to avoid leaving your home.

And no, you don’t need a face mask unless you have COVID-19 and are showing symptoms. Buying up masks takes away precious materials from the health workers who need them most.

Who is most at risk of becoming very sick or dying?

The general American public is at low risk of contracting COVID-19, according to the CDC.

Those at a higher risk of exposure to the virus include people who live in communities that are seeing sustained transmission, health care workers caring for COVID-19 patients and close contacts of patients.

As with seasonal flu, people at highest risk for severe disease and death include people aged over 60 years and those with underlying conditions such as hypertension, diabetes, cardiovascular disease, chronic respiratory disease and cancer, according to the WHO.

In China, the median age of coronavirus patients is 51 years old, and the majority of cases (78%) were 30 to 69 years, according to February study conducted by the WHO. The highest mortality rate was among people over 80 years of age.

Coronavirus outbreak in Washington state nursing home highlights risk among senior citizens

Does coronavirus affect pregnancy?

It’s unclear how the coronavirus may affect pregnant women. In general, pregnant women may experience changes to their body that could make them more susceptible to viral respiratory infections, according to the CDC.

In the case of SARS and MERS, pregnant women were more at risk for severe illness, and some experienced miscarriage and stillbirth, according to the CDC.

There is no evidence that the virus can be transmitted from an infected mother to her fetus, and, in a limited number of recent cases of infants born to mothers with COVID-19, none of the infants have tested positive for the virus, the CDC said.

Can kids get coronavirus?

Coronavirus in children appears to be rare, with about 2% of cases reported among people under 19 years old, according to the WHO study in China. An even smaller proportion of this age group developed severe (2.5%) or critical disease (0.2%), and just one person under 20 had died in China as of February.

How do you talk to children about coronavirus? Stay honest and simple to avoid anxiety.

Coronavirus vs. flu: How many people die from flu each year?

In the U.S., influenza has caused 12,000 to 61,000 deaths annually since 2010, according to the CDC.

So far this flu season in the U.S., there have been at least 36 million flu illnesses, 370,000 hospitalizations and 22,000 deaths from flu, according to the CDC. At least 144 of those deaths were in children.

Why is this being compared to the 1918 flu pandemic? What are the similarities and differences?

The Spanish flu, an H1N1 virus, emerged in the wake of WWI and spread across the globe between 1918 and 1919, infecting about a third of the world’s population. An estimated 50 million people died, with about 675,000 deaths in the U.S., according to the CDC.

Unlike COVID-19, the 1918 pandemic had a high mortality rate among young, healthy people aged 20 to 40. While the Spanish flu’s mortality rate was at least 2.5%, with some estimates as high as 10%, the mortality rate of COVID-19 appears to be closer to 3.4%, based on reported cases.

Like COVID-19, the main protections against the 1918 pandemic included isolation, quarantine, personal hygiene, use of disinfectants, and limitations of public gatherings, according to the CDC.

How did the coronavirus start?

Coronaviruses are a large family of viruses, named for their crown-like spikes. In rare cases, coronaviruses in animals have infected people, who spread the virus to other people. That’s what happened with Middle East Respiratory Syndrome, or MERS, and Severe Acute Respiratory Syndrome, SARS, two far deadlier coronaviruses.

COVID-19, originally called the “novel coronavirus,” was first detected in December 2019. The first infection was linked to a market in Wuhan, China, a city of 11 million people. It’s still unclear how transmission unfolded, but there are several theories.

Some researchers believe that someone bought contaminated meat at the market, ate it, got sick and infected others. Others say the virus originated in bats, spread to an intermediary animal, and then to humans. Some researchers say pangolins may have been that intermediary host.

How is coronavirus spread? How long does coronavirus stay on surfaces?

The virus is spreading rapidly from person to person, and scientists are still learning more about how it spreads. According to the CDC, the virus spreads between people who are in close contact with one another (within about 6 feet) and through respiratory droplets, much like the common cold or flu.

See how coronavirus moved from one person to many in a matter of days

There’s no evidence that the virus can be transmitted through food, and there is likely very low risk of spread from food products or packaging that are shipped over a period of days or weeks, according to the CDC.

It is, however, possible that a person can get the virus by touching a surface or object that has the virus on it and then touching their own face. A recent study by scientists in the U.S. found that viable virus could be detected up to three hours later in the air, up to four hours on copper, up to 24 hours on cardboard and up to two to three days on plastic and stainless steel.

USA TODAY analyzed three case studies that show how the virus was transmitted from person to person.

Is there a vaccine? Can coronavirus be cured?

There are no drugs or vaccines for coronaviruses, including COVID-19. Doctors can only treat the symptoms the viruses cause.

Chinese scientists have decoded the COVID-19 DNA and made it public, and several pharmaceutical companies in the U.S. and abroad are working to develop a vaccine. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, estimated that a vaccine will be ready within 12 to 18 months.

What is the treatment for coronavirus?

Treatment consists of supportive care to help relieve symptoms and, for severe cases, care to support vital organ functions, the CDC says.

About 80% of people recover from the disease without needing special treatment, according to the WHO. For most patients, that means drinking plenty of fluids and resting, just as you would for the cold or flu.

How long does coronavirus last?

Patients are infectious as long as they are “actively sick.” But how long someone is actively sick can vary, according to the CDC.

Information about how long symptoms last is still evolving. But the February WHO study may give us some preliminary clues:

• The median time from symptom onset to recovery is about two weeks for mild cases
• For patients with severe or critical disease, the median recovery time is three to six weeks
• Among patients who have died, the time from symptom onset to death ranges from two to eight weeks

How do I get a coronavirus test?

If you’re not quarantined on an air base or cruise ship, the only way to get a coronavirus test is through a health care professional.

Call your doctor if you have a fever, develop virus symptoms, have recently traveled to an area with an ongoing spread of the virus or have come into contact with a person who is known to have it. You may be asked to wear a mask to the office.

If your doctor thinks you might have the coronavirus, he or she will contact the CDC or your local health department for instructions on testing.

Who can actually test for coronavirus?

As of March 12, 81 state and local public health laboratories in 50 states and the District of Columbia have successfully verified COVID-19 diagnostic tests and are offering testing, according to the CDC. Both academic labs and large private lab testing companies such as LabCorp and Quest Diagnostics are rolling out coronavirus tests after receiving FDA authorization.

While the CDC initially developed and mailed flawed testing kits, the agency said it fixed the glitch. Now, a new shortage of a key testing component is causing delays.

Meanwhile, a project funded by billionaire Bill Gates is set to issue at-home testing kits for people who fear they have been infected with the coronavirus.

How will it affect our economy? Will the stock market ever recover?

The COVID-19 outbreak is taking a growing toll on the U.S. economy, and the stock market has fluctuated wildly. At the end of February, the Dow Jones Industrial Average lost 3,500 points in a single week, and the Dow and S&P 500 had their worst performance in a week since October 2008. In March, U.S. stocks collapsed again, with the Dow plummeting by more than 2,000 points. On Thursday, the S&P 500 slid into bear territory for the first time since the financial crisis.

In an emergency response, the Federal Reserve cut interest rates on March 3 – the Fed’s first rate cut between scheduled meetings since the depths of the financial crisis in 2008. The Fed said it would continue monitoring developments.

Consider this: Can the Fed save the economy, and your 401k, from the coronavirus?

What is the Trump administration doing about the epidemic? What is Mike Pence’s role?

At the end of January, the Trump administration declared the coronavirus outbreak to be a public health emergency in the U.S. and quarantined Americans who had recently been to certain parts of China – the first quarantine order issued by the federal government in more than 50 years.

President Donald Trump put Vice President Mike Pence in charge of a task force that is coordinating the government’s response to the outbreak. Trump also signed an emergency funding bill to combat the spread of coronavirus in the U.S. and help treat people who become ill. The $8.3 billion funding package amounts to one of the largest packages Congress will have passed to combat a global health crisis.

On Wednesday, Trump said he would use emergency authority to defer payments on federal loans to small businesses and to defer taxes for businesses hurt by coronavirus.

What’s going on with cruises?

Dozens of confirmed cases have cropped up aboard cruise ships in recent weeks, and many other cases across the U.S. have been linked back to cruises.

In February, more than 700 passengers from the Diamond Princess became infected after the ship was held in quarantine off the coast of Japan. Of roughly 300 Americans evacuated from the ship and returned to the United States, 46 tested positive. Though most have ended their 14-day quarantine at U.S. military bases, some have remained in medical isolation as they recover.

Another ship, the Grand Princess, finally docked Monday after being held off the coast of San Francisco. Of the more than 3,500 people on board, at least two passengers and 19 crew members have tested positive for the virus. Hundreds of Americans on board were expected to be taken to quarantine for two weeks.

Major cruise lines including Carnival, Royal Caribbean, Norwegian, and Celebrity announced they would suspend sailing operations to and from U.S. ports for 30 days, Cruise Lines International Association announced Friday.

COVID-19 updates in your inbox: Sign up for USA TODAY’s Coronavirus Watch 

What does it mean to quarantine versus isolate?

Isolation and quarantine are effective ways to help prevent the spread of disease, according to the CDC. Isolation separates sick people with a contagious disease from people who are not sick. Quarantine separates and restricts the movement of people who were exposed to a contagious disease to see if they become sick.

Will US schools close?

At least 15 states and a number of large urban school districts — including Los Angeles, the nation’s second-largest — are shutting down all K-12 schools as part of a sweeping attempt to contain the spread of the coronavirus.

Alabama, Florida, Kentucky, Illinois, Louisiana, Maryland, Michigan, New Mexico. Ohio, Oregon, Pennsylvania, Virginia, West Virginia, Wisconsin, Washington have all ordered all schools closed.

More than 100 colleges have canceled in-person classes and moved online.

Should I cancel my upcoming events?

Concerts, shows, games and conferences have been canceled and businesses, museums, resorts and theme parks have been closed across the globe to prevent the continued spread of the virus. In the U.S., individual state and local governments are assessing the risk of large gatherings. So, should you cancel upcoming events, like weddings?  We talked to experts for some tips. 

Follow Grace Hauck on Twitter @grace_hauck.

Contributing: Erin Richards, David Jackson, John Fritze, Michael Collins, John Bacon, Jorge Ortiz, Paul Davidson, Adrianna Rodriguez, Jayne O’Donnell, Ken Alltucker, Jessica Menton, Ryan Miller, Morgan Hines, David Oliver, Dawn Gilbertson, Curtis Tate, Jayme Deerwester.