Measles(麻疹), which once killed 450 children each year and disabled even more, was nearly wiped out in the United States 14 years ago by the universal use of the MMR vaccine(疫苗). But the disease is making a comeback, caused by a growing anti-vaccine movement and misinformation that is spreading quickly. Already this year, 115 measles cases have been reported in the USA, compared with 189 for all of last year.

The numbers might sound small, but they are the leading edge of a dangerous trend. When vaccination rates are very high, as they still are in the nation as a whole, everyone is protected. This is called "herd immunity", which protects the people who get hurt easily, including those who can't be vaccinated for medical reasons, babies too young to get vaccinated and people on whom the vaccine doesn't work.

But herd immunity works only when nearly the whole herd joins in. When some refuse vaccination and seek a free ride, immunity breaks down and everyone is in even bigger danger.

That's exactly what is happening in small neighborhoods around the country from Orange County, California, where 22 measles cases were reported this month, to Brooklyn, N.Y., where a 17-year-old caused an outbreak last year.

The resistance to vaccine has continued for decades, and it is driven by a real but very small risk. Those who refuse to take that risk selfishly make others suffer.

Making things worse are state laws that make it too easy to opt out(决定不参加) of what are supposed to be required vaccines for all children entering kindergarten. Seventeen states allow parents to get an exemption（豁免), sometimes just by signing a paper saying they personally object to a vaccine.

Now, several states are moving to tighten laws by adding new regulations for opting out. But no one does enough to limit exemptions.

Parents ought to be able to opt out only for limited medical or religious reasons. But personal opinions? Not good enough. Everyone enjoys the life-saving benefits vaccines provide, but they'll exist only as long as everyone shares in the risks.

In 1990, Hal Donaldson was 23 years old, fresh out of college and found himself in Calcutta, India, where he was asked to interview Mother Teresa.

Donaldson says about the great woman famed for feeding the hungry, "She wasn't wearing shoes and her ankles were swollen. She sat down with me and was very polite." After the interview. Mother Teresa asked him, "What are you doing to help the poor?" Donaldson admitted that he was young and wasn't focused on helping others. With a smile on her face, Mother Teresa said. "Everyone can do something."

Those words deeply struck Donaldson and forced him to face some hard truths about himself.

Hal Donaldson grew up in the San Francisco Bay area. When he was 12 years old, his parents were hit by a drunk driver; his father died, and his mother was seriously injured. To make ends meet, they went on welfare. Donaldson says. "I had holes in my shoes and clothes. When you're teased at school for that, you just want to escape."

He managed to do just that. Donaldson got into college and turned his focus to making money for himself. He says, "I was just trying to find my way out of insignificance. However, it's easy to overlook others along the way. I was the guy that would see a homeless person and cross the street, so I didn't have to confront(面对)him. My focus was on climbing to the top instead of helping those trying to climb with me."

Donaldson returned home from India with a different thought. He traveled to eight cities in America and stayed on the streets and listened to stories of the homeless. "My heart broke," he says. "I knew I could no longer just live for myself."

Inspired by Mother Teresa's words and the stories he'd heard across America, Donaldson loaded a pick-up truck with $ 300 worth of groceries and handed them out to anyone who needed help. In 1994, Donaldson created the nonprofit organization, Convoy for Hope, which works with communities across America and around the world. Their work focuses on feeding children, women's empowerment, helping farmers and disaster services.

Octopuses (章鱼) in the wild have often been observed changing their skin color to catch their food or avoid being caught. Now, for the first time, a researcher has shot an attractive video of an octopus called Heidi rapidly changing into a quantity of colors while dreaming. 

The video, part of Octopus: Making Contact, a documentary first shown on PBS on

October 2, 2019, was shot by a fish lover David Scheel, who has raised Heidi in a fish tank since she was young. The professor at Alaska Pacific University in Anchorage believes that the octopus — whose skin went from pale gray to ghostly white to deep, dark violet, before changing into a greenish-brown camouflage (伪装) pattern — was dreaming of catching her next meal. 

" She's asleep; she sees a crab (螃蟹), and her color starts to change a little bit, " Scheel says in the video. " Then she turns all dark. Octopuses will do that when they leave the bottom. " He adds. " This is a camouflage like she's just caught a crab, and now she's going to sit there and eat it, and she doesn't want anyone to notice her. If she's dreaming, that's the dream. " Scheel's theory about Heidi's pleasant dream originates from the fact that animals with the ability to camouflage have never been observed changing colors so abruptly while sleeping.

The hour-long documentary, which tracks Scheel's developing relationship with the octopus, also shows Heidi's other skills. She enjoys playing with small toys, watching television — particularly The Big Bang Theory — and solving puzzles. The talented octopus can also escape from small spaces, use tools, and even press a button on a remote control. Like any smart family pet, Heidi recognizes Scheel and his teenage daughter Laura and excitedly rushes to her tank's side in greeting every time either comes close.