COVID-19, the illness caused by a new kind of coronavirus, has dramatically altered life as we know it in the United States. Schools have closed, businesses have shut down, people have been forced into isolation and left with uncertainty.

What started as a small outbreak in Wuhan, China, months ago has now spanned the globe. And still, medical and public health officials in scores of countries are racing to find answers.

This is a guide to the things we do know, from scientists, doctors and public health experts — a resource that changes alongside our understanding of this virus.

Who can get novel coronavirus, or COVID-19?

People all over the world and of all ages can get COVID-19 or spread the virus. NBA players, members of Congress, even actors are among the hundreds of thousands of people who have been infected. Fewer infants, children and young adults have died or gotten seriously ill so far, but they are not immune.

What happens if you get the virus?

The majority of people recover, according to data from China and other countries. Many people report mild or moderate symptoms. But “mild” is relative — some patients with so-called mild cases have still reported feeling very sick. Patients who have severe cases of COVID-19 may get pneumonia. The World Health Organization estimates 3 to 4 percent of cases lead to death.

Who is most at risk?

Early data, which the Centers for Disease Control and Prevention warns is limited, suggests that people at the greatest risk of getting really sick or dying from COVID-19 are older or have pre-existing health conditions, including heart disease, lung disease, diabetes and other chronic illnesses. In the U.S., four out of five deaths from the disease, nearly half of all hospitalizations and more than half of all intensive care admissions have been among people 65 and older, according to a report from the CDC.

What are the most common symptoms?

  • Fever or chills
  • Dry, persistent cough
  • Shortness of breath or difficulty breathing
  • Fatigue or malaise
  • Sore throat

From the time you are exposed, symptoms could appear within two to 14 days (but most commonly it’s about five days, WHO says). A smaller number of patients have reported headaches, nausea or diarrhea. Some people get the virus but appear to have no symptoms, putting them at greater risk for passing it to others. Or symptoms can be easily confused with the seasonal flu, which has also complicated efforts to identify and contain COVID-19.

What should you do if you or someone at home has symptoms?

First and foremost, stay at home even if you’re not the person who is sick. The CDC recommends “social distancing” for two weeks, which is the length of time believed to be the disease’s incubation period. The sick person should stay in a room away from other people, and if possible, use a separate bathroom. Continue to wash your hands, clean and disinfect high-traffic hard surfaces (door knobs, countertops, faucet handles) and don’t share food or drinks.

Contact your medical care provider online or by phone to seek guidance. If you are not experiencing a medical emergency, do not rush to a clinic before you speak with a provider. If you are struggling to breathe, go to an emergency room immediately.

How does novel coronavirus spread?

It spreads through airborne respiratory droplets, i.e. saliva and mucus, and can be transmitted from surfaces that someone has coughed on or touched. To reduce your chances of getting or spreading the virus, practice good hygiene:

  • Cover your nose and mouth when you sneeze or cough
  • Avoid touching your face
  • Avoid touching surfaces
  • Wash your hands thoroughly with soap and warm water for at least 20 seconds

How often do I need to wash my hands?

Wash your hands immediately after blowing your nose, coughing, sneezing, using the bathroom or touching surfaces in a public space. Wash your hands before eating or preparing food and before touching your face. If you’re not sure you’re doing it right, here’s what the CDC recommends:

  • Wet your hands with clean, running water
  • Rub your hands together with soap — this includes the backs of your hands, between your fingers and under your nails
  • Scrub your hands for as long as it takes to sing the “Happy Birthday” song twice
  • Rinse your hands under clean, running water and dry them with a clean towel or air dryer

How does it compare to the flu?

Novel coronavirus belongs to the same family of viruses as the common cold, not influenza. But the symptoms can be similar to flu, and the current pandemic has drawn comparisons to the 1918 influenza that killed up to 50 million people around the world.

The flu, which returns every year, sickens many more people in the U.S. than COVID-19 — so far. Unlike the flu, COVID-19 does not have a vaccine or medications designed specifically to prevent and treat it. If you haven’t gotten your flu shot this season, health officials urge you to do so now, as soon as possible.

This novel coronavirus appears to have a higher mortality rate, based on current data. You calculate that rate by dividing the number who have died from COVID-19 by the number overall who are sick. But because testing is far from adequate, public health officials, especially in the U.S., have trouble with figuring out exactly how many people have this virus.

Who can get tested? How do you get tested?

It’s not as easy as simply asking for one. It depends on where you live, how many tests are available in your community, how sick you are and if you have reason to believe that you might have the virus. Without an abundance of tests currently available across the U.S., testing may be reserved for those who are presenting respiratory systems, have had contact with someone with a confirmed case of COVID-19 or health care providers who tended to a patient with the virus.

If you have reason to suspect you could have COVID-19, the CDC says you should call your primary care physician, local community health center or urgent care facility. Providers will ask you about your symptoms and, if they believe you should receive testing, advise you as to whether, how and where to seek testing. But multiple people have reported that their doctors have referred them to their state or local health departments for COVID-19 testing, but said they were unable to access a test.

What is “social distancing”?

In short, it means not socializing with anyone outside your household, and limiting your trips to places where you might interact with other people to only what is absolutely necessary (to work, if your job is essential, and to the grocery store or pharmacy if you must). If you can, the CDC recommends keeping a two-week supply of medications, food and other essentials on hand.

The Trump administration has also advised against gatherings of more than 10 people. And if you are around other people, keep at least six feet apart, make sure to cover your mouth and nose when you sneeze and cough, and don’t share food or drinks. Many parks and playgrounds have closed, but you can take a walk or go out into nature if you keep your distance from others. And, of course, keep washing your hands.

How can I help others?

Counterintuitively, the best way to help others and society at large right now is to isolate yourself, stay home as much as possible and avoid the unintentional spread of the virus. You’ll be helping everyone, particularly those in the highest-risk groups and health care workers. There are many funding campaigns that have already been set up to help many businesses and workers.