On February 18, 2020, members of a police sanitation team spraying disinfectant as a preventive measure against the spread of the Covid-19 coronavirus in Bozhou, in China’s eastern Anhui province. | Photo by STR/AFP via Getty Images

Is it safe to travel? Is this going to become a pandemic? How will the outbreak end?

The coronavirus outbreak, centered in China, keeps evolving at a dizzying speed. With the case toll rising steeply (reaching over 75,000 on February 19), face masks flying off store shelves, and businesses, cruise ships, and entire cities upended by the virus — it’s no wonder questions and fears are swirling about Covid-19, as the disease is known.

For most people in the US, however, there’s no reason to worry: Ninety-nine percent of cases are happening in China. But that may shift in the coming weeks as more outbreaks are detected in other countries. Here are answers to your most burning questions about the new coronavirus and its risks.

1) What is this new coronavirus and where did it come from?

 Universal Images Group via Getty Images
Coronaviruses owe their name to the crown-like projections, visible here under microscope, that encircle the capsid.

Coronaviruses are a large family of viruses that typically attack the respiratory system. The name comes from the Latin word corona for crown and the Ancient Greek korōnè, meaning garland or wreath, because of the spiky fringe encircling these viruses. Most coronaviruses infect animals, such as bats, cats, and birds. Only seven, including Covid-19, SARS, and MERS, are known to infect humans.

SARS is thought to have evolved from infecting bats to civet cats to humans in China; MERS evolved from bats to camels to humans in the Middle East. No one knows precisely where Covid-19 came from, though the leading hypothesis is that bats were once again the original source: they spread the virus to pangolins, and pangolins to humans.

2) What are the symptoms?

Greater Horseshoe Bat (Rhinolophus ferrumequinum)...DeAgostini/Getty Images
The leading hypothesis is that bats were the original source of the new coronavirus.

Two of the seven coronaviruses that infect humans, SARS and MERS, can cause severe pneumonia and even death in 10 and more than 30 percent of cases, respectively. But the others lead to milder symptoms, like a common cold.

At the moment, we know Covid-19 can cause pneumonia and that it too can kill — but while it seems to be less deadly than SARS and MERS, it’s not yet clear by how much.

Some of the best evidence on the question comes from a February 16 China CDC report looking at the outcomes of the first 72,314 patients with confirmed or suspected Covid-19 in mainland China. It’s the largest such analysis to date. And it found an overall case fatality rate of 2.3 percent — lower than both SARS and MERS. (The case fatality rate, or CFR, is the proportion of deaths a disease causes within a group of people who have the disease.)

The researchers also discovered a huge variation in the case fatality rate by age group. In short, the virus appears to be more deadly in people with each passing decade. You can see the trend in this table from the study:

 China CDC
Case fatality rates in mainland China as of February 11, 2020.

Overall, the researchers characterized 81 percent of the cases as mild, and 19 percent as severe or critical.

One major caveat, though: This data comes from mainland China, where all but a few of the 2,012 deaths have occurred. And for reasons no one understands, the case fatality rate has been lower outside of mainland China.

At the same time, there’s also evidence of asymptomatic cases. And it’s possible that as we discover more of these cases, Covid-19 will seem more like seasonal flu than like SARS. That’s because infectious diseases typically look more severe when they’re first discovered, since the people showing up in hospitals tend to be the sickest.

As for symptoms: According to the Centers for Disease Control and Prevention, most patients start with a fever, cough, and shortness of breath.

A report, published in The Lancet, provided more detailed information. It looked at a subset of the first 41 patients with confirmed Covid-19 in Wuhan, China, the mainland Chinese city of 11 million where the outbreak is believed to have started.

The most common symptoms were fever, cough, muscle pain, and fatigue; less common were headache, diarrhea, and coughing up mucus or blood. All had pneumonia and lung abnormalities on CT scans. As for the disease severity: 32 percent were admitted to an ICU, and 15 percent died. By January 22, most (68 percent) of the patients had been discharged from the hospital.

3) How do coronaviruses spread?

We don’t yet know how exactly Covid-19 spreads, but we do have a lot of data on how MERS, SARS, and other respiratory viruses move from person to person. And that’s mainly through exposure to droplets from coughing or sneezing.

So when an infected person coughs or sneezes, they let out a spray, and if these droplets reach the nose, eyes, or mouth of another person, they can pass on the virus, said Jennifer Nuzzo, an infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security. In rarer cases, a person might catch a respiratory disease indirectly, “via touching droplets on surfaces — and then touching mucosal membranes” in the mouth, eyes, and nose, she added. That’s why hand-washing is an important public health measure — all the time, and especially in an outbreak.

4) Should I travel while this outbreak is going on?

 Filippo Monteforte/AFP via Getty Images
A tourist wearing a respiratory mask at the Trevi Fountain in downtown Rome on January 31, 2020. The Italian government declared a state of emergency to prevent the spread of the new coronavirus after two cases were confirmed in Rome.

Both the CDC and the State Department have issued their highest-level travel alerts for China, advising Americans to avoid traveling there for the moment. (These advisories are likely to change as the outbreak evolves, so keep checking them.)

And that’s not only because there’s a risk of catching this new virus. Right now, numerous airlines are canceling or scaling back flights to China, in part because of decreased demand. Countries are also forcing returning visitors from China into quarantines. “I’m more concerned about the unpredictability of the [outbreak] response at this point,” Nuzzo said. “It would not be fun to go to China and get stuck there somehow. And coming back, you’ll be subject to additional screening [or quarantines].”

But people worried about travel should remember that these advisories focus on China, where the epidemic is currently playing out.

Of the cases right now, 99 percent are in mainland China. And more than half of those are in Hubei. “The risk of acquiring this infection outside of Hubei and, truly, outside of China is remarkably low,” said Isaac Bogoch, a professor at the University of Toronto who studies how air travel influences the dynamics outbreaks — including the new coronavirus infection.

Source: Johns Hopkins University Center for Systems Science and Engineering

What if you have to travel and you’re seated near someone who is sick? That’s not time to panic, either. “There has been some work looking into the risk of acquiring infectious diseases through air travel,” Bogoch said. “The risk of acquiring a respiratory infection through air travel is still extraordinarily low.”

The risk does go up if you happen to be seated within six feet of a person with a respiratory infection. But even there, simple proximity doesn’t necessarily mean you’ll catch anything. Instead, the more infectious the person is, and the longer you sit near them, the higher your risk. If you’re not near the person for very long, or they’re not very infectious, the risk is lower. And again, it’s unlikely that sick person has the coronavirus.

5) I’m still worried about the new coronavirus. What should I do to protect myself? Buy a face mask?

 Tayfun Coskun/Anadolu Agency via Getty Images
People wear medical masks as a precaution against coronavirus, walking around New York, on January 30, 2020.

In the US, the risk to the public is currently deemed low. And just about every health expert Vox has spoken to has said there’s little evidence to support the use of face masks for preventing disease in the general population.

Masks are only useful if you have a respiratory infection already and want to minimize the risk of spread to others, or if you’re caring for someone who is sick or working in a hospital in direct contact with people who have respiratory illnesses. (Plus, there are reports of runs on masks and other supplies health workers need to stay safe.)

That’s why the CDC advises against the use of masks for regular Americans. “The virus is not spreading in the general community,” Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, reasoned in a press briefing on January 30. But people are hoarding them anyway, and for the wrong reasons.

The best thing you can do to prevent all sorts of illnesses, Messonnier said, is “wash your hands, cover your cough, take care of yourself, and keep alert to the information that we’re providing.”

6) What about the cases of people spreading the virus before they show symptoms? Isn’t that worrisome?

Germany China Health CoronavirusPhoto by TF-Images/Getty Images
Webasto, a German car parts supplier with manufacturing centers in China. People working at the company were the first to become infected with the virus in Germany.

The best evidence that the virus can spread before a person has symptoms came from Germany. But there were problems with the initial analysis.

The outbreak there was first identified in Bavaria on January 27, when a German businessman was diagnosed. He had been in meetings with a female colleague who was visiting from Shanghai and had the virus but didn’t know it. The woman, according to a New England Journal of Medicine case report, only began to feel symptoms — such as fever and a cough — after she left Germany, and days after meeting with the German businessman. This suggests she may have transmitted the virus to the man before knowing she was sick.

If this were true, it’d throw a wrench in the attempts to stop the virus from spreading, since it suggests people who don’t even know they’re infected can spread the disease.

But it turns out the researchers published this report without having spoken to the woman. And within days of publication, the Robert Koch Institute — Germany’s public health agency — wrote a letter to NEJM about an error in the study, according to Sciences Kai Kupferschmidt, who broke the story. The public health researchers followed up with the woman and found out she actually did have symptoms while in Germany. She “felt tired, suffered from muscle pain, and took paracetamol, a fever-lowering medication,” Kupferschmidt explained.

This doesn’t mean that we won’t still find out people can spread the virus asymptomatically. More evidence could still surface, and some believe it will. However, Bogoch said, “even if there have been cases of asymptomatic transmission of this infection, those will be typically rare cases, and with just about every other respiratory tract infection known to humankind, those are not the people who are driving an epidemic.”

7) Is this going to become a deadly pandemic?

 Fabrice Coffrini/AFP via Getty Images
WHO Director-General Tedros Adhanom Ghebreyesus, right, with WHO Health Emergencies Program head Michael Ryan at a press conference following a WHO Emergency committee to discuss whether the new coronavirus constitutes an international health emergency, on January 30, 2020, in Geneva.

For now, the CDC and WHO are still calling this an outbreak. Very soon, though, health experts may determine that there are enough cases in China to officially call the outbreak an epidemic. And if the disease continues to spread locally in other countries, it could turn into a pandemic (which is defined as an epidemic that’s spread to two or more regions of the world).

On February 10, the WHO’s director general, Dr. Tedros Adhanom Ghebreyesus, flicked at that possibility. He noted there were cases outside of China, which included “concerning instances of onward transmission from people with no travel history to China.” These “could be the spark that becomes a bigger fire.”

But a disease can spread widely, and become a pandemic, without being particularly severe. And no one knows yet what a Covid-19 pandemic would look like — mostly because we don’t yet know precisely how lethal this disease is.

If you take the current number of deaths and divide it by the number of known cases, “the case fatality is 2 percent — and it’s gone down from 3 percent in the early days,” said University of Michigan’s Howard Markel, who studies outbreaks. “And if it goes really, really low, we’ll probably say — like we did in Mexico in 2009 with [H1N1] swine flu — that it’s something very similar, if not less deadly, [to] regular seasonal flu.”

So once more of these mild cases are discovered, this virus could look a lot less deadly.

“We live [with] and tolerate a whole lot of respiratory viruses,” Nuzzo said, “some of which are even more transmissible than the estimates people have come out with for this one — but they don’t make the headlines.”

8) Is my city at risk of an outbreak?

 Ian Forsyth/Getty Images
Two women wearing face masks on January 31, 2020, in Newcastle upon Tyne, England.

Some of the best research on that question comes from Bogoch and his colleagues. They’ve done studies in the past couple of weeks on the cities most vulnerable to novel coronavirus infections. What’s the big takeaway?

It’s really East Asia and Southeast Asia that are most at risk.

The researchers — from the University of Oxford, University of Toronto, and London School of Medicine and Tropical Hygiene — used 2019 data from the International Air Transport Association to find all the cities in China that received at least 100,000 airline passengers from Wuhan during February through April.

They then modeled how the disease could spread from those cities if they experienced local outbreaks. Here are 15 of the top 50 destinations that might see outbreaks (also pay attention to the IDVI — the Infectious Disease Vulnerability Index — number. It’s a measure of a country’s ability to manage an infectious disease. Scores closer to zero mean they’re less prepared.)

 Oxford Journal of Travel Medicine

“By no means would anybody be surprised if there are more cases exported to Europe and the US,” Bogoch said. “But the places that are going to have the greatest volume and number of infections exported would be to East Asian and Southeast Asian centers.”

9) So what might happen next?

If China contains the virus, and the outbreaks in other countries don’t blow up, we might see the case count start to fall and the public health emergency fizzle out.

But there are already so many cases across China, as well as the very real possibility that the virus is circulating, undetected, in other countries — especially those with with weak health systems — that the possibility of containment is looking less likely by the day.

If Covid-19 is not contained, “if it continues to accelerate, we very well may have a pandemic,” said Tony Fauci, the head of the National Institute of Allergy and Infectious Diseases. That would mean more sickness and deaths not only in China, but also in other countries around the world, as cases grow from one-off travelers or small clusters to full-blown outbreaks.

In this scenario, he added, “you don’t try to control [the virus] because it’s already everywhere.” So public health officials would move from attempting containment of the virus to mitigating its impact — setting up hospitals to isolate and care for patients, making recommendations for “social distancing” (like canceling public events), and coming up with triaging protocols for the many people who might need hospital care.

But again, even if this virus moves around the world, it may not do much harm. In the best-case scenario, this outbreak might look more like H1N1 swine flu. When H1N1 was first recognized in 2009 and spread around the world, there were major concerns about its lethality. US schools closed, people from North America were quarantined when they arrived in other countries, flights were canceled. Not only did those measures fail to contain the virus, Nuzzo said, it turned out H1N1 wasn’t all that deadly.

“Now we’re still living with that virus — it’s one that circulates with every flu season,” Nuzzo explained.

10) How is the world responding to this crisis?

On January 30, the WHO declared the outbreak a global public health emergency. Though it advised countries not to put in place travel or trade restrictions against China, several — including Russia and Singapore — have already sealed their borders. Meanwhile, the US government dramatically escalated its response — issuing its highest-level travel advisory, quarantining citizens evacuated from China, and temporarily banning foreign nationals who have recently been to the East Asian country from coming in.

These extreme measures can be explained, in part, by all the unknowns related to this virus: leaders are taking extreme precautions for fear Covid-19 is very deadly and can spread very far.

The measures can also be explained by the fact that we have no enforceable international law governing outbreak responses. So countries can basically do what they want in response to pandemic threats without getting penalized, even if the WHO advises against whatever actions they’re taking.

That appears to be the case in China, where the most dramatic — and unprecedented — response is currently playing out. “China has implemented the most extensive cordon sanitaire [or quarantine] in the history of humankind,” Lawrence Gostin, a global health law professor at Georgetown University, told Vox. “They’ve restricted movements, caused fear and panic. They’ve violated human rights.”

Authorities there have also censored information and silenced the whistleblowers who tried to sound the alarm sooner than Chinese authorities were willing, and kicked out foreign journalists critical of China’s outbreak response. But again, because of the weakness of global health law, the international community has remained mostly silent about these actions.

11) How might this end?

There are a few ways this outbreak could end, as my colleague Brian Resnick explained. Perhaps public health measures — identifying cases fast, putting infected people in isolation — will stop the spread of this coronavirus. (That’s what stopped the spread of SARS in 2003.)

Because this is a zoonotic disease, meaning it came from an animal, finding and eliminating that source would also help. Or maybe a vaccine or antiviral will be invented quickly to curb a broader epidemic (though that’ll likely take years).

The coming seasons of warmer weather could also play a role in at least slowing the virus down. “Coronaviruses are winter viruses,” Fauci said. “When the weather is warm and moist, these viruses don’t spread as well as when the weather is cold and dry.”

Finally, there’s the possibility the virus will simply die out. “Disease outbreaks are a bit like fires,” Resnick wrote. “The virus is the flame. Susceptible people are the fuel. Eventually a fire burns itself out if it runs out of kindling. A virus outbreak will end when it stops finding susceptible people to infect.”


Listen to Today, Explained

A SARS-like virus has sickened thousands in China, and made its way to the United States. Vox’s Julia Belluz explains what’s known and what’s next.

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