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Concerns are growing about the deadly new virus behind a fast-spreading epidemic in China. The number of people ill with or dying of a viral pneumonia caused by the new coronavirus is rising rapidly, despite quarantines of millions of people and other measures to try to stop it. The virus has been carried by travelers to other countries.
Very little is known about this virus, which for the moment carries the scientific name 2019-nCoV, meaning “novel coronavirus.” Scientists are racing to learn more. Key questions to answer are how long the incubation period is, how long someone is infectious, and whether or not people can be asymptomatic and spread the virus.
Here is what scientists and public-health officials know so far.
How dangerous is the new coronavirus?
It appears to be less deadly than a related pathogen — severe acute respiratory syndrome, or SARS, which erupted in China in 2002 and spread globally in 2003. SARS killed about 10% of the people it infected, while about 3% of the people confirmed to be infected with this new coronavirus have died. Many of those who have died are elderly or have other illnesses such as diabetes.
But the new virus may spread from one person to another more easily than SARS, some early disease modeling suggests.
What is a coronavirus?
This new virus belongs to a family of viruses known as coronaviruses. Named for the crown-like spikes on their surfaces, they infect mostly bats, pigs and small mammals. But they mutate easily and can jump from animals to humans, and from one human to another. In recent years, they have become a growing player in infectious-disease outbreaks world-wide.
Seven strains are known to infect humans, including this new virus, causing illnesses in the respiratory tract. Four of those strains cause common colds. Two others, by contrast, rank among the deadliest of human infections: SARS and Middle East respiratory syndrome, or MERS.
Coronaviruses: From Animals to Humans
Researchers aren't sure from what animal the novel coronavirus originated or whether it passed through an intermediate species before infecting humans.
Where did this new coronavirus come from?
The new virus likely came from bats, scientists say. It isn’t known exactly where or how it jumped to humans, though. Health officials believe the outbreak originated in a large animal and seafood market in Wuhan, China.
Of the first 41 cases, 27 had some exposure to that market. But three of the first four people to become ill, on Dec. 1 and Dec. 10, said they had no contact with the market. Scientists say it will take some time to identify the exact source.
How is the virus spread among humans?
It is likely spread through a cough, kiss or other contact with saliva, Chinese officials say. MERS and SARS spread mainly through “respiratory droplets” produced when someone coughs or sneezes. Those two viruses spread mostly through close contact.
Can face masks protect you?
Health experts and mask makers say only a properly used reusable N95 respirator mask certified by an independent agency can both guard against the virus and protect others. Paper or polyurethane foam masks don’t filter out smaller particles responsible for transmitting infectious agents.
How Effective Are Masks?
The World Health Organization and other experts report that a mask's efficacy in social settings is inconclusive. But some health experts and mask makers say that properly used, the N95 respirator mask can guard against the new coronavirus.
A coronavirus can also be transmitted by touching an object where airborne droplets have settled.
The viruses can survive briefly on surfaces depending on conditions of humidity and temperature.
Wearing a mask prevents direct contact with nose and mouth, and could protect a user who may have touched a contaminated area.
Frequently changing disposable masks, and washing your hands after, are important steps to avoid contamination from pathogens that cling to the outer surface.
N95 masks offer more protection. But they only work if they fit properly, and aren’t suitable for children or people with facial hair.
Surgical masks don’t offer full protection against airborne viruses. They don’t fully seal off the nose and mouth.
How easily does the new virus spread?
Disease-modeling experts at Imperial College London estimated late last week that on average, each infected person transmitted the virus to 2.6 others. The World Health Organization said last week early indications were that that rate is between 1.4 and 2.5. Those rates are higher than for some influenza viruses, but far lower than measles, in which one infected person can transmit the virus to 12 to 18 other people.
Is it safe to travel to China?
The U.S. State Department has issued a travel advisory, urging Americans to reconsider travel to China due to the risk of infection in Wuhan as well as quarantines imposed in numerous cities around the country. The CDC recommends avoiding all nonessential travel to China. Those individuals who do go should avoid contact with sick people, animals, animal markets and uncooked meat from those markets, the CDC says.
Should foreigners who are working in China or planning on visiting change their plans?
Companies in China are trying to head off the spread in their offices.
Can you catch the virus from someone even before they have symptoms?
It’s possible. But little is known so far. In Macau, a 15-year-old resident of Wuhan, the epicenter of the outbreak, tested positive for the coronavirus despite having no fever or cough, said that special administrative region of China. Scientists reported in the Lancet that they identified the coronavirus in a 10-year-old boy who developed no symptoms, even though others in the child’s family fell ill. Chinese news outlets have reported a handful of other potential asymptomatic cases.
How the First Patients Fared
By Jan. 2, Researchers identifed 41 novel coronavirus patients who had been admitted to the hospital in Wuhan, China.
MOST COMMON EARLY SYMPTOMS
What are the symptoms of illness and how do you know if you have it?
The virus infects the lower respiratory tract. Patients initially develop a fever, cough and aches, and can progress to shortness of breath and complications from pneumonia, according to case reports. Some patients become only mildly ill. Others are mildly ill for a few days, then rapidly develop more severe symptoms of pneumonia.
Some patients have not had a fever initially or develop a “walking pneumonia,” meaning they may spread their infection to others because they aren’t sick enough to be in a hospital.
What is the incubation period?
People become ill between two and 14 days after infection, according to the U.S. CDC.
Is there a test?
Public-health officials have developed and distributed diagnostic tests, which are being used to confirm whether a patient has the new coronavirus or another infection. The growing availability of tests is one reason more people are being diagnosed.
Who is most at risk?
Adults of all ages have been infected. Nearly three-quarters of the initial 41 patients were male. Many of the first patients who died were over 60 years old, had other illnesses such as diabetes and were admitted to hospitals when their illness was advanced. Few children have been reported with the infection, but that could change.
Is the virus mutating, particularly in a way that would make it more contagious?
No. The virus has remained stable genetically thus far, according to the World Health Organization and the U.S. CDC.
What is being done to contain the spread of the virus?
China imposed quarantines on Wuhan, the epicenter of the outbreak, and several other cities, affecting millions of citizens. Officials are also building a large field hospital in Wuhan to isolate and care for patients, and investigating chains of transmission. But these measures are failing to slow the spread.
Many people left ahead of the quarantine. The new virus hit during a heavy travel period for China, when tens of millions of people visit family and sometimes tack on additional leisure travel. The mayor of Wuhan, whose population is 11 million, said Sunday that five million people had left. It isn’t known how many of those people were fleeing the virus or just embarking on holiday trips.
Hong Kong now requires visitors from mainland China to fill out health declaration forms before entering the city through the airport or high-speed rail station and is working to implement that at other points of entry, according to city authorities. Hong Kong Chief Executive Carrie Lam said Saturday that health authorities are also working to screen more aggressively for fevers at the border.
The U.S. is screening passengers arriving from Wuhan at five major airports. Those who have a fever are then screened for other symptoms. U.S. officials are considering expanding the screening, but haven’t provided details.
Are there drugs to treat coronaviruses?
There aren’t any drugs or vaccines approved specifically for the new virus. No antiviral treatment has proven effective against coronaviruses. But one hospital in Wuhan has started a clinical trial using a combination of two drugs that had been tested on MERS patients in Saudi Arabia. The therapy, sold under the brand name Kaletra in the U.S., is normally used to treat HIV patients and belongs to a class of drugs known as protease inhibitors, which block a key enzyme that helps viruses replicate. Researchers are also investigating other antivirals. In addition, a few vaccine makers are developing products targeting the virus.
Could goods imported from China carry the virus?
That’s unlikely, the CDC says. Coronaviruses generally don’t survive long on inanimate surfaces, according to the agency.