(left to right): JOHN WESSELS/AFP/GETTY IMAGES; ASTRID GAST/SHUTTERSTOCK.COM; ISTOCK.COM/BRAUNS

Top stories: Ebola outbreak challenges, Viking cats, and a new kind of placebo

Ebola vaccine is having 'major impact' but worries about DRC outbreak grow

Concerns about an Ebola outbreak in the Democratic Republic of the Congo that surfaced in August are growing. Although communities seem to be responding well after more than 40,000 people received an experimental vaccine for the disease, the outbreak in the northeastern region of the country is in an area that has long suffered from armed conflict, which repeatedly has brought Ebola response teams to a halt.

Viking cat skeletons reveal a surprising growth in the size of felines over time

Many animals shrink when they become domesticated, but a curious thing appears to have happened to cats during the Viking era: They got bigger. By examining Denmark’s feline fossil record, researchers found domesticated cats grew on average by about 16% between the Viking Age and today. The researchers suspect the cats’ growth was related to a plentiful supply of food from growing villages.

Just thinking you have poor endurance genes changes your body

In a study examining what may be a novel form of the placebo response, psychologists have found that just telling a person they have a high or low genetic risk for certain physical traits can influence how their body functions when exercising or eating—regardless of what genetic variant they actually have.

NIH says cancer study also hit by fetal tissue ban

A team investigating cancer immunotherapy is the third laboratory affected by President Donald Trump’s administration’s order telling scientists at the U.S. National Institutes of Health (NIH) to stop acquiring new human fetal tissue for experiments. Last week, two experiments investigating HIV and eye diseases, respectively, were put on hold. The order is now being reviewed by the Department of Health and Human Services, which oversees NIH.

After botched launch, orbiting atomic clocks confirm Einstein’s theory of relativity

Two teams of physicists have used data from misguided satellites to put Albert Einstein’s theory of gravity, the general theory of relativity, to an unexpected test. The opportunistic experiment confirms to unprecedented precision a key prediction of the theory—that time ticks slower near a massive body like Earth than it does farther away.