A new drug compound can successfully speed up rehabilitation for animals recovering from a stroke, according to research published in Science Thursday. If it works in humans, it could eventually extend the time for repairing some brain functions after stroke, Eileen Drage O'Reilly reports.

The big picture: An estimated 1.7 million people suffer a traumatic brain injury in the U.S. every year and almost 800,000 of those are from a stroke. Strokes kill 140,000 people a year and are the leading cause of serious long-term disability, CDC says.

Timing is key: "We believe there is a 'window of time' (about 3 months) for plasticity to allow motor recovery," Argye Elizabeth Hillis, neurology professor at Johns Hopkins University School of Medicine who was not part of the study, tells Axios.

"People currently recover to varying degrees, but stroke remains one of the most common causes of disability in adults," Hillis says.

Read the full story here.

The overall chances of dying from an infectious disease are decreasing in the U.S., but the probability can vary greatly from county to county, according to data recently published in the Journal of the American Medical Association.

The bottom line: Overall death rates dropped between 1980 and 2014 for HIV/AIDS, tuberculosis and other infectious diseases. But from 2000 to 2014, deaths from diarrhea-related diseases increased in the U.S. That may be largely because of bacteria that has become resistant to antibiotics.

"We want people at the local level to take this information and use it to make decisions, and not to be fooled by state average numbers."

Read the key takeaways.

• Oh, Canada: The country recruited 24 top academics in quantum computing, genetics, AI and other disciplines to move their research activities there, Steve LeVine reports.
• China's Tiangong-1 space station, which fell into the Pacific Ocean last weekend, was the country's first step in becoming a space superpower, Erica Pandey writes. "In the next two decades, look for China to spend even more to increase its presence."
• Puerto Rico: The government there currently estimates the death toll from Hurricane Maria to be 64 people. But new research puts the number closer to 1,085, Eileen reports. The underreported deaths are "essentially limiting necessary financial and other aid resources," she writes.
• Space: Relativity, a startup developing an “automated process for manufacturing and launching entire rockets from conception to production,” has raised $35 million in new venture capital funding, Dan Primack writes. The company aims to slash space launch costs by 3D-printing the rockets and many boosters.

• Genetics and intelligence: MIT Tech Review's Antonio Regalado on studies linking DNA variations to intelligence, the controversy surrounding genetic IQ tests and the prospect of picking smart embryos. The bottom line: "Right now, the polygenic [DNA] scores capture only a fraction of the genetic determinants of intelligence and none of the environmental ones. That means the predictions remain fuzzy."
• CRISPR: A paper published last year in Nature Methods that reported the gene-editing tool caused unintended mutations was retracted last week.
• The riddle of trees: A gem from Knowable's Rachel Ehrenberg about the struggle to define what exactly a tree is.
• (Halfway) across the universe: Astronomers spot the farthest star yet, per NASA. The light from Icarus took 9 billion years to reach the Hubble Space Telescope and is from a time when the universe was just 30% of its current age, offering researchers a glimpse into its evolution.

Whether winter or summer, bowhead whales stick to the Arctic Ocean. Beneath the ice, in frigid waters and 24-hour darkness for months, the intimate details of their 200-year-long lives are practically off-limits for scientists — and largely unknown.

From 2010–2014, the University of Washington's Kate Stafford and her colleagues at the Norwegian Polar Institute collected data using underwater microphones in the North Atlantic's Fram Strait, where one of the Arctic's four populations of bowhead whales resides.

"From November to early April, the whales were screaming their heads off under the ice. It was super unexpected and super cool," Stafford says.

Unlike humpback whales that collectively sing more or less the same song over a season, the repertoire for bowheads is more vast and diverse: the researchers found the population of about 300 whales sang 184 distinct songs over the three years. Some were sung for a few hours or days but rarely ever more than a month. Over the winter breeding season, the whales sang multiple different songs. The following year, they changed it up altogether.

“Bowhead whales are completely different. And I have no idea why,” Stafford says.

What it sounds like: Each song lasts 45 seconds to 2 minutes but can be repeated to make a long bout of singing, Stafford says. Their frequency ranges from 50 Hz up to 5000 Hz. "They scream, cry, whine, purr, moan, shout."

The unknown: Without visually studying the whales as they sing, Stafford says it's unknown whether individual animals are producing different songs, whether they are sung exclusively by males and for what purpose (for instance, scientists assume that, like in humpbacks, it is related to mating), or why they change songs.

Go deeper: Read Krista Langlois' piece in Hakai on the relationship between whales and indigenous people.