What began with a handful of mysterious illnesses in a central China city has traveled the world. First detected on the last day of 2019, the novel coronavirus has killed more than 330,000 people with infections surpassing five million worldwide. It has triggered nationwide lockdowns, stock market upheaval and dangerous conspiracy theories.
Most cases are mild, but health officials say much is still unknown about the virus that causes the disease covid-19.
The Washington Post has spoken to scores of doctors, officials and experts to answer as many of your questions as we can about the newest global health emergency. Here’s what we know so far.
What is it?
These days, “coronavirus” is often prefaced with the word “novel,” because that’s precisely what it is: a new strain in a family of viruses we’ve all seen before — and, in some form, had. According to the WHO, coronaviruses are a large family of viruses that range from the common cold to much more serious diseases. These diseases can infect both humans and animals. The strain that began spreading in Wuhan, the capital of China’s Hubei province, is related to two other coronaviruses that have caused major outbreaks in recent years: severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).
Symptoms of a coronavirus infection range in severity from respiratory problems to cases of pneumonia, kidney failure and a buildup of fluid in the lungs. They may appear 2 to 14 days after exposure to the virus.
In April, the CDC added new symptoms of the disease to its list, shedding more light on how the virus infects patients. The symptoms now include: a cough, shortness of breath, fever, chills, repeated shaking with chills, muscle pain, headache, sore throat and a loss of taste or smell.
Covid-19 spreads more easily than SARS and is similar to other coronaviruses that cause cold-like symptoms, experts have said. It appears to be highly transmissible, and since cases are mild, the disease may be more widespread than current testing numbers suggest.
How deadly is it and who is most at risk?
Public health officials say the novel coronavirus is less deadly than SARS, which killed about 10 percent of people who were infected during the outbreak that began in 2002. But epidemiologists are still trying to determine exactly how deadly covid-19 is.
Similar to other respiratory illnesses, older people and those with illnesses such as diabetes and high blood pressure are at increased risk. Data show that the virus is killing more men than women in the U.S.
But, as with other diseases, there can be tremendous individual variation in how people respond. There will be people with known risk factors who recover as well as people who develop severe cases for reasons we don’t understand.
There’s also no evidence that children are more prone to contracting covid-19, according to the CDC, and that was also the case with the disease′s cousins, SARS and MERS.
How does it spread?
The coronavirus primarily spreads from person to person and not easily from a contaminated surface. In updated guidance issued in late-May, the CDC said the virus spreads “easily and sustainably” between people. The agency added that contaminated objects, surfaces and infected animals do not appear to be significant modes of transmission.
The virus travels through the droplets a person produces when talking or coughing, the CDC website says. An individual does not need to feel sick or show symptoms to spread it.
How should I protect myself?
There are some basic precautions you can take, which are the same as what you should be doing every day to stave off other respiratory diseases. You’ve seen the guidance before: Wash your hands regularly. Cover your nose and mouth when you sneeze. And when you’re sick, stay home from work or school and drink lots of fluids.
The CDC recommends washing with soap and water for at least 20 seconds after using the bathroom, before eating and after blowing your nose or sneezing. It also advises not to touch your eyes, nose and mouth and to clean objects and surfaces you touch often.
What’s it like to have covid-19?
Symptoms are primarily respiratory. Coughing and shortness of breath are common, according to the CDC. Fever is also possible. The severity of the symptoms depends highly on the patient’s age and immune system.
For the elderly and those with underlying heart disease, diabetes or other conditions, coronavirus can cause pneumonia and lead to organ failure and death. But for most people, cases have been mild, requiring little to no medical intervention.
Should I see a doctor?
It is a good idea to call your primary-care doctor if you have both a fever and a cough, experts said. And if you have shortness of breath, unremitting fever, weakness or lethargy, it’s definitely time to get in touch with a health-care professional, they say. Those could be signs of pneumonia, which is common in severe cases of coronavirus.
The Centers for Disease Control and Prevention also recommends that you seek medical help if you recently traveled to a coronavirus-infected area or had close contact with a known infected person and have a fever, a cough or trouble breathing.
How can I get tested?
If you have mild symptoms, you probably won’t be. If you are sick enough to be hospitalized, you’ll likely get tested. If you are in the middle group, it’s unclear.
And even as more tests are being manufactured and shipped around the country, many public health labs receiving them don’t have enough staff or equipment to meet the testing need. Some medical centers are offering their own tests, and some primary care doctors are exploring how to administer the tests in their offices, but many are reluctant because it carries risks for their staff and other patients.
Other hospitals and localities are setting up testing locations away from emergency rooms, clinics and doctors’ offices to minimize the risk of health care workers and other patients being infected. And, in declaring a national emergency, Trump said the administration will work with retailers like Walmart and Target to develop drive-through testing clinics across the country.
How long will I have to social distance?
The most honest answer, according to experts, is: “It depends.” It’s not going to be over anytime soon — a matter of months rather than weeks. And a few key factors will determine just how many months.
First, it depends on when U.S. cases finally reach their peak — a time that’s impossible to predict because of how limited testing remains in America. And even after the peak, we may need drastic actions to keep the virus at bay. It also depends on how the virus behaves, and whether it’ll be affected by the change of seasons like the flu.
But, ultimately, how well America is able to flatten and bend its epidemiological curve of infections depends largely on how willing people will be to sacrifice individual conveniences and on their desire to save the lives of others.
“I don’t know if people are ready now for how long they’re probably going to have to keep up this social distancing,” said Natalie Dean, a biostatistician at the University of Florida. “But as they see the hospital situation get more extreme, I think that attitude will change.”
What does a stay-at-home order mean and how long will it last?
This depends on where you live. Almost all states issued a sweeping directive, but in some places, cities and counties enacted their own measures. In all, 315 million Americans were affected. Most orders allowed residents to leave their homes to shop for groceries and other essentials, to exercise outdoors, to go to the doctor and to pick up prescriptions. But each jurisdiction had its own list of do’s and don’ts.
Georgia, Tennessee and Florida were among the first states to begin lifting restrictions — a move that experts and math models say will almost certainly lead to more infections and deaths. Other places, like New York City and California, have taken a more cautious approach. The Post is keeping track of how states reopen.
Should I wear a mask?
President Trump announced new guidance in April that people in the U.S. wear face coverings in public to slow the spread of the coronavirus, a reversal of the administration’s earlier recommendations.
The guidance makes clear that wearing face coverings or cloth masks is an additional public health measure to prevent the spread of the virus, not a substitute for social distancing. Social distancing of at least six feet is still recommended even when wearing a mask. Guidance and internal memos from CDC emphasize that a cloth facial mask is intended not so much to protect the wearer but to help prevent people who do not know they are infected from spreading of the virus to others.
The new CDC guidance was prompted by increasing evidence that infected people without symptoms can spread the coronavirus. Simple cloth masks that cover the mouth and nose can prevent virus transmission from such individuals when they are out buying groceries, where people may come into closer contact, for example.
When will it end?
This coronavirus could follow a seasonal pattern, peaking in the winter months. It could infect lots of people now and then recede in the Northern Hemisphere before returning in the fall.
“This virus can do anything it wants,” said Allison McGeer, an infectious-disease epidemiologist at the University of Toronto. “That pattern of how it’s going to spread is completely unknown, but it is critical to what the burden is going to be to all of us. … It could be just like another coronavirus, a bunch of colds. It could be like a regular flu season. It’s possible it could be different and worse.”
Terms to know
Coronavirus: This term refers to a family of seven known viruses that can infect people, ranging from the common cold to severe acute respiratory syndrome (SARS) and the even deadlier Middle East respiratory syndrome (MERS). The name comes from the virus’s shape, which under a microscope looks like a blob surrounded by crown-like spikes.

Covid-19: Sometimes used interchangeably with coronavirus and the official name SARS-CoV-2, covid-19 refers to the disease the virus causes. So SARS-CoV-2 causes covid-19, just as HIV causes AIDS.
Community transmission: This happens when a disease circulates among people in a certain area who did not travel to an affected location and have no close link to other confirmed cases.
Asymptomatic transmission: Asymptomatic carriers of the virus are people who show no signs of being sick but have the virus and can spread it to others.
Outbreak: A sudden increase in the number of cases of a disease in a particular place and time.
Epidemic: A large outbreak that spreads among a population or in a region.
Pandemic: An epidemic that has become rampant in multiple countries and continents simultaneously.
Flattening the curve”: A phrase that experts use when talking about the need to use protective measures to slow the spread of new cases. It refers to the powerful visual illustration seen on a statistical chart. A flattened curve is the difference between a viral outbreak that has the profile of Mount Everest, exploding vertically, and one that slowly unfolds over time — a long, low hill.
Containment: In the early phases of an epidemic, countries often use this strategy of trying to corral and beat back the advance of a virus in hopes of limiting its spread and possibly stamping it out. They restrict movement of people, enact travel bans and quarantine. To use a military analogy, it is treating new cases like a beachhead invasion and surrounding and beating back each new beachhead.
Mitigation: Once it’s clear you’re dealing with widespread transmission that will be difficult if not impossible to contain, authorities begin focusing instead on wider preparations like getting hospitals ready to handle influx of patients, stockpiling materials and enacting social distancing policies.
Isolation: Keeping those who are sick and infected away from those who aren’t is referred to as isolation. Hospitals have taken strict measures to isolate coronavirus patients using isolation wards, ventilators that prevent air from circulating more widely and heavy protective gear for health workers.
Quarantine: Restricting the movement of people who seem healthy but may have been exposed to the virus is known as quarantine. Americans who were evacuated from Wuhan and cruise ships, for example, have been kept in strict quarantine on military bases for 14 days, which is what experts believe is the virus’s incubation period.
Zoonotic: The new coronavirus was transmitted from animals to people, making it zoonotic. SARS came from civets, which are like cats, and MERS came from camels, but it’s not yet known what animal caused the current coronavirus outbreak. The prime suspect so far is the pangolin.