Sleep trackers have become increasingly popular, but for some people, perfecting their sleep score becomes an end unto itself. Yiu Yu Hoi/Getty Images hide caption
Your body needs trace amounts of zinc for cell division and other basic biology. Karl Tapales/Getty Images hide caption
American evacuees from the Diamond Princess cruise ship arrive at Joint Base San Antonio-Lackland on Monday in San Antonio, Texas. Edward A. Ornelas/Getty Images hide caption
June (left) and Mary Kelly with a photo of their mother, Marilyn Kelly. Marilyn was living at Our House Too, in Rutland, Vt., before she died. James Buck/VPR/Seven Days hide caption
A man gets tested for diabetes at an event in Dhaka, Bangladesh, for World Diabetes Day in 2019. Mehedi Hasan/NurPhoto via Getty Images hide caption
Disposable vapes may be hotter than Juul among kids, according to researcher Bonnie Halpern-Felsher. She received a bag of vape pens recently confiscated by a high school principal in northern California, with flavors like Banana Ice and Cool Mint. Bonnie Halpern-Felsher hide caption
Buses arrive at Yokohama Port, near Tokyo, as the Japan Self-Defense Forces prepare to move American passengers from the quarantined Diamond Princess cruise ship on Sunday. Jae C. Hong/AP hide caption
Ethan Howard was among 235 people in the southern Indiana community of Austin, Ind., to be infected with HIV in an outbreak that hit in 2015. It was fueled by injection drug use. Luke Sharrett/Kaiser Health News hide caption
Passengers walk along the deck of the Diamond Princess cruise ship, on which about 3,600 people have been quarantined because of fears of the new COVID-19 coronavirus. Charly Triballeau/AFP via Getty Images hide caption
On Feb. 4, beds were installed in the Wuhan Keting Exhibition Center. With 2,000 beds planned, the center will accommodate patients with mild cases of COVID-19. Stringer for NPR hide caption
A federal appeals court has upheld a ruling that blocked work requirements in Arkansas and in Kentucky, which has since rescinded them. Secretary of Health and Human Services Alex Azar is seen testifying before the Senate Finance Committee on Thursday. J. Scott Applewhite/AP hide caption
President Trump and Chinese President Xi Jinping attend a bilateral meeting on the sidelines of the G20 Summit in Osaka last June. The two leaders spoke by phone earlier this month. Since the coronavirus outbreak, China has let in some experts from the World Health Organization but has not yet allowed in a team from the U.S. Centers for Disease Control and Prevention. Brendan Smialowski/AFP via Getty Images hide caption
A masked Yoda and Pikachu guard a table with signs notifying evacuees of times for daily temperature checks. Chunlin Leonhard hide caption
A bus departs from the dock where the Diamond Princess cruise ship sits under quarantine with its thousands of passengers and crew. Japanese authorities said Friday that some older passengers who tested negative for the coronavirus were allowed to disembark. Charly Triballeau/AFP via Getty Images hide caption
A doctor wearing a face mask looks at a CT image of a lung of a patient at a hospital in Wuhan, China. AFP via Getty Images hide caption
A passenger (right) is hugged by Cambodia Prime Minister Hun Sen after she disembarked from the MS Westerdam at the port of Sihanoukville, Cambodia, on Friday. Heng Sinith/AP hide caption
In this image from a scanning electron microscope, the new coronavirus is in orange. NIAID-RML hide caption
The first U.S. case of COVID-19 was treated at Providence Regional Medical Center in Everett, Washington. Robin Addison, a nurse there, demonstrates how she wears a respirator helmet with a face shield intended to prevent infection. Ted S. Warren/AP hide caption
Students Caleb Lam (left), 15, and Kevin Ng, 16, have been taking online classes since the schools shut down. ""You have nothing to do at home after classes. We chat online," Lam says. Meredith Rizzo/NPR hide caption
Where should you sit on a plane to reduce the risk of exposure to germs spread by infectious passengers? skaman306/Getty Images hide caption
A man wearing a face mask has his temperature checked before entering a community hospital in Shanghai on Thursday. China's official death toll and infection numbers from the deadly COVID-19 coronavirus spiked dramatically on Thursday after authorities changed their counting methods. Noel Celis/AFP via Getty Images hide caption
The scientific community has lots of feelings about emoji representation. Geologists are excited about the new rock emoji, for example, but reviews are mixed when it comes to the fly. Emojipedia hide caption
The city of Wuhan, epicenter of the current coronavirus outbreak. Jia Yu/Getty Images hide caption