Pien Huang

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."

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.

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.

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.

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.

Brian Lapointe, a research professor at Florida Atlantic University's Harbor Branch Oceanographic Institute, has spent his career studying corals at the Looe Key Reef, in a National Marine Sanctuary in the Florida Keys.

Over that time, he's witnessed an alarming trend. In the past 20 years, half of Florida corals have died off.

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