What you need to know about coronavirus

Note: All statistics in this story are current as of 8:30 p.m. Oct. 27 and will be updated regularly.

Health authorities are closely watching an outbreak of respiratory illness caused by a new strain of coronavirus known as COVID-19. Here are the answers to key questions about the outbreak:

What is the virus?

Scientists have identified the virus as a novel, or new, coronavirus. The name comes from the Latin word for crowns or halos, which coronaviruses resemble under a microscope. The coronavirus family has many strains that affect people. Some cause the common cold, while some originating in bats, camels and other animals have evolved into more severe illnesses such as SARS — severe acute respiratory syndrome — or MERS — Middle East respiratory syndrome.

Where did it come from?

The first cases of COVID-19 appeared in Wuhan, in central China’s Hubei province. Many of the first people infected had visited or worked at the Huanan Seafood Wholesale Market in Wuhan, which has since been closed for an investigation. Chinese health officials say they think the illness first spread from animals to people.

How widespread is it?

More than 244 million cases of COVID-19 have been confirmed around the world, according to Johns Hopkins University. The vast majority of the early cases were in China — where the rate of new cases has slowed drastically — and Brazil, India and the United States have since become hotspots. In the United States, which has the biggest reported outbreak of any nation, more than 45.7 million cases have been confirmed.

How deadly is it?

More than 4.9 million people have died from the virus, making the mortality rate about 2.0% among confirmed cases. By comparison, the mortality rate for the seasonal flu is generally about 0.1%. Experts say inconsistencies in reporting cases have made it difficult to precisely determine the mortality rate. Also, in some places, only the most critical patients were tested at the onset of the pandemic, and many people with mild or no symptoms may never be tested. Experts have said the virus’ true mortality rate may be closer to 1%.

What are the symptoms?

Common symptoms include fever, dry cough and fatigue. Shortness of breath, chills and body aches are associated with more dangerous cases of coronavirus, according to the U.S. Centers for Disease Control and Prevention. In serious cases, the virus can cause pneumonia. The virus and the flu have similar symptoms and transmission methods, so they can be hard to tell apart.

How is it treated?

Scientists have found evidence that some treatments can help patients with coronavirus symptoms. Among them are the antiviral drug remdesivir, the anti-inflammatory drug dexamethasone and convalescent plasma from recovered patients.

What about a vaccine?

Three vaccines for the coronavirus are being distributed in the United States The immunizations from Pfizer and Moderna, which each require two doses, are both about 95% effective, and neither has raised serious safety concerns in trials of tens of thousands of volunteers. Johnson & Johnson’s vaccine has a lower efficacy but only requires one shot.

How accurate are different types of tests?

PCR tests, which are more common and usually involve a nasal swab — but may also be performed with saliva — are more accurate, according to health experts, but are so sensitive that they may detect the virus even after a person has recovered. Antigen, or rapid, tests are more likely to produce false negatives. PCR tests are estimated to be 99% accurate under ideal conditions, while antigen tests are estimated at 93%.

How is it spreading?

Many coronaviruses can spread through coughing or sneezing, or by touching an infected person. Scientists say the virus can spread from person to person in close contact through the respiratory tract, and they have confirmed airborne transmission.

What is community spread?

Most of the early local cases of COVID-19 were travel-related, but in some cases patients hadn’t been to areas where there are outbreaks. Community spread means that someone has been infected with the virus but health officials aren’t sure where or how. Social distancing aims to prevent community spread of the disease.

Should you wear a mask?

The CDC has recommended that people wear face coverings in public settings where it may be difficult to maintain social distancing, such as grocery stores. The guidance is based on studies that show that many people infected with the coronavirus can spread it before they show symptoms, or even without ever showing symptoms.

Does hand sanitizer kill it?

Experts say frequent hand-washing with soap and water is the best way to prevent the spread of disease. Hands should be washed for at least 20 seconds after people sneeze, cough or use the restroom and before eating. If soap and water aren’t available, the CDC says hand sanitizer that contains at least 60% alcohol is an acceptable alternative.

How do you stop touching your face?

Washing your hands and not touching your face are basic prevention tips against the virus. People tend to touch their eyes, nose and mouth, places the virus can easily enter the body. To avoid this, trying using a tissue or wearing gloves, putting your hands away, setting reminders or recording yourself.

How should you prepare your home?

Experts say you should buy extra shelf-stable foods, such as rice, beans and canned goods, so you won’t need to go to the grocery store as often. Also make sure to have enough of your prescription medication on hand. For cleaning, household cleaners should be effective disinfectants.

What if someone in your home is sick?

If someone in your home has the coronavirus, you should stay home to prevent spreading the disease, health officials say. Don’t have visitors, and try to separate the sick person from healthy residents — including giving them their own bedroom and bathroom, if possible. Clean and disinfect surfaces regularly, and take extra precautions with laundry.

Can you get coronavirus twice?

Reports of people testing positive for the virus after recovering from COVID-19 have occurred. Health experts have said that while people who recover may develop some immunity, it may not last long enough to prevent re-infection.

The Associated Press contributed to this report.

For more information about how Johns Hopkins University tracks coronavirus cases, visit the university’s blog post.