Pien Huang

In communities where most coronavirus tests are coming back positive, it's a sign there are many more cases there that haven't been found, say World Health Organization officials in a press conference on Monday.

"If 80-90% of the people test positive, you are probably missing a lot of cases," says Michael Ryan, executive director of the WHO Health Emergencies Program.

As the new coronavirus continues to spread around the globe, researchers say the virus is changing its genetic makeup slightly. But does that mean it is becoming more dangerous to humans? And what would the impact be on any future vaccines?

The fact that the novel coronavirus appeared in the middle of flu season has prompted inevitable comparisons. Is COVID-19, the disease caused by the virus, pretty much similar to the flu or does it pose a far greater threat?

Although there are still many unknowns about COVID-19, there is some solid information from researchers that sheds light on some of the similarities and differences at this time.

Symptoms

On Weibo, the Chinese version of Twitter, user 一只猫叫鱼Yu kept a public diary of her lockdown experience in Wuhan, China. On day 29, she described losing track of time. "I watch the days go by one after another," she wrote. "I don't know how long days like this are going to last."

Updated on March 17 at 5:06 p.m. ET

Mild.

Moderate.

Serious.

Severe or extreme.

These are some of the adjectives being used to describe the symptoms displayed by patients with COVID-19. Vice President Pence used them in his remarks to the nation last week:

"Some — some large percentage have mild flu symptoms; some have serious flu symptoms."

Keep your distance. And don't kiss.

Those are two pieces of advice that could be crucial in reducing the spread of the coronavirus.

Public health officials say the spread has been mainly driven through people spending time indoors with others who have the disease.

"Looks like the main driver is not widespread community infection — looks like it's household-level infection," Dr. Bruce Aylward, a senior adviser to the World Health Organization, said at a news conference in Geneva on Feb. 25.

Updated Feb. 21, 11:46 a.m. ET

Last month, a British man went to a conference in Singapore, then on a ski trip to the French Alps.

What he didn't know when he arrived in the Alps was that he was infected with the virus behind the COVID-19 outbreak.

During his stay at a ski village, it appears he infected 11 other people, who subsequently traveled on to the U.K. and Spain, the World Health Organization says.

Updated on March 6 at 3:45 p.m.

It's the season for colds and flus — and a newly identified respiratory disease, COVID-19.

To cut your risk of catching a respiratory illness on your next flight, experts offer two pieces of common-sense advice: Wash your hands frequently and keep a distance from people who are sick.

Where to sit to prevent getting sick

A 2018 study suggests that to minimize contact with other passengers, you should pick a window seat and stay put.

Like Ebola virus in Africa and the Nipah virus in Asia, the new coronavirus — 2019-nCoV — appears to have originated in bats.

Chinese researchers took samples of the coronavirus from patients in Wuhan, the city in central China where the outbreak was first detected.

They compared the genetic sequence of the new coronavirus — 2019-nCoV — to a library of known viruses and found a 96% match with a coronavirus found in horseshoe bats in southwest China. The findings were published in a study in Nature this week.

Updated at 8:20 p.m. ET

Public health officials around the world were responding to the fast-growing outbreak of the new coronavirus, as officials in China, at the epidemic's epicenter, announced that the number of cases there had reached nearly 6,000.

The World Health Organization announced that it would send international health experts to China to help understand the outbreak and guide the response.

Updated at 12:26 p.m. ET

Saturday's Lunar New Year celebrations were dampened in China by fears over the coronavirus outbreak and travel restrictions affecting 46 million people.

On the first day of the Lunar New Year, China's President Xi Jinping stressed the urgency of controlling the outbreak — which has seen hundreds more confirmed cases since Friday — and urged state authorities to prioritize containment efforts.

"I don't feel in the Chinese New Year mood at all this year," a netizen with username 朱一龙qwertyuiop416 posted this week on Weibo, China's equivalent to Twitter. "I'm panicking. I'm getting more scared every day."

That sentiment reflects a trend on Chinese social media as confirmed cases of the Wuhan coronavirus surge.

Initially, there was some lightheartedness in posts. One Weibo user commented it was "the perfect time" to stay home and play a mobile phone game called Plague Inc.

Updated on Jan. 17 at 2 p.m.

Three U.S. airports will begin screening passengers from Wuhan, China, for symptoms of the new strain of coronavirus — named 2019-nCoV — that has been discovered in China.

2019 is a record year for dengue fever in Latin America. The mosquito-borne disease has surged across the continent, from Mexico down to Chile and Argentina, with nearly 3 million cases reported.

You'd think that as a poor country grows wealthier, more of its children would get vaccinated for preventable diseases such as polio, measles and pneumonia.

But a review published in Nature this month offers a different perspective.

You might think that the more you clean, the less germy your home is.

That's what Laura-Isobel McCall, a biochemist at the University of Oklahoma, thought she'd find when she started comparing microbes between rural and urban homes in Peru and Brazil.

"We expected that all the microbes would actually become less diverse with urbanization, and that's not at all what we found for the fungi," she says.

Alexandra Chen was a trauma specialist working in Lebanon and Jordan when she noticed that a specific group of kids were struggling in schools.

Chen kept getting referrals for refugee students who had fled the war in Syria. They were having trouble focusing and finishing schoolwork. Some had even dropped out of school.

Better vaccines, nutrition and disease control have cut the global death rate for children in half over the past 20 years. But even within countries that have made major progress, children can face greatly different fates.

"Where you're born substantially impacts your probability of surviving to 5," says Simon Hay, an epidemiologist at the University of Washington who is the lead author of a new study on childhood mortality in Nature.

In 2015, Zika virus swept through Brazil and the Americas. It was the first time a mosquito-borne virus was known to cause severe birth defects, and the World Health Organization declared it a "public health emergency that warranted a global response."

Viktoriia Radchuk, an evolutionary ecologist at Berlin's Leibniz Institute for Zoo and Wildlife Research, wanted to know how animals were responding to climate change.

So she scoured the results of more than 10,000 animal studies — on species from frogs to snakes, from insects to birds to mammals — looking for information on how changing environments were affecting animal behavior. Based on the available data, she decided to focus on birds in the Northern Hemisphere.

Precision medicine is the field of dreams for human health. Drugs and treatments that would take into account a person's individual DNA configurations, as well as lifestyle and environment, would presumably be better tailored to each person's needs. Still, while the goal of precision medicine is to help everybody, the current research available has a major flaw. It's largely based on the genes of people who are predominantly of white and European descent.

The world's glaciers are melting faster than before, but it still takes decades to see changes that are happening at a glacial pace.