【推荐1】The starting point of herd immunity (群体免疫) for COVID-9 is still uncertain , but many epidemiologists (流行病学家) believe it will be reached when between 60 percent and 80 percent of the population has been infected and develops resistance. A lower level of immunity in the population can slow the spread of a disease somewhat, but the herd immunity number                    represents the point where infections are generally less likely to turn into large outbreaks.

Studies that use the tests to examine only a small quantity of population, often called serology (血清学) surveys, are being undertaken around America and the world. The purpose of these new studies is to look for antibodies (抗体) in people’s blood, proteins produced by the immune system that indicate a past infection.

An advantage of the tests is that they can pick out people who may have been infected and didn’t know they were sick. A disadvantage is that the tests are sometimes wrong---and several studies, including a notable one in California, have been criticized for not taking the possibility of inaccurate results into consideration or for not representing the whole population.

While these studies are far from perfect, many countries, including parts of Sweden, are on track to achieve so-called herd immunity from the novel coronavirus-caused COVID-19 disease within weeks. In general, they give a better sense of how far the coronavirus has truly spread and its potential for spreading further. The starting point of herd immunity may differ from place to place, depending on factors like density and social interaction.

【推荐3】The waste management park at Water Beach in Cambridge-shire handles 400,000 tons of recycling every year.

Fran Hawes is standing on the edge of a mountain of dry recycling. She says, “Some think it’s a discouraging thing, but for me personally, it is a huge responsibility.” Fran, who started to do the job at the age of 26, takes her job very seriously. “I am that annoying person at a party who will get everyone’s recycling and make sure everything goes in the right bin,” she admits. “That’s my job. That’s my mission. That’s what I need to do. It allows me to find my leadership style.”

Bin loader Richard Hughes and his colleagues clock on at the waste service garage in Peter-borough at 6:30 and are out emptying bins within half an hour. Richard works four 12-hour days and admits the pay and the condition are not great—but there are three days off which he can spare to his partner and children. His colleague Crystal Teal has been working as a bin loader for two and a half months. “I didn’t feel my last job gave me self-worth and general happiness, so I decided to change and do something completely different,” she says. “I decided to be a binman. It doesn’t bother me that men are mainly doing it,” Crystal adds. “It can be smelly some days, but go home and have a shower, you’ll be all right.”

“When householders put the wrong material in the recycling bins, it makes me feel angry that they are just putting it out there. We’re doing our job to serve them. We are providing service to take their rubbish away and they can’t do their part to put the right things in,” said Richard.

“Any problem has a solution—therefore I’m not afraid of a pile of waste,” Fran says. “To any normal person, this might be intimidating (令人生畏的). It’s a challenge. But this will be gone by Monday morning.”

【推荐3】The Catnapper Mystery

Cody, the catnapper, had a talent for taking cats from trees, yards, and porches. He’d keep them until their owners paid for their return. One day, Milly’s kitten Mousie was missing. Milly accused Cody. “No way!” said Detective Denny. “I saw Cody catch a train to Planters Plain this morning. Mousie can’t have been kidnapped (绑架) by Cody!”

“There are no paw prints on my lawn,” noted Milly. “Mousie didn’t just scamper off!”

“And there are no sneaker prints,” said Detective Denny. “Cody only wears sneakers.” Then he noticed tiny holes in the grass that looked like they were made by high-heeled shoes. Denny pulled out a pencil. He was very careful as he measured the holes. “Half a pencil deep! Only Patty Perry’s Pet Shop wears heels that high and thin.”

Milly and Detective Denny ran to Patty’s, where a man was loading pets into a van. “Where are these animals going?” asked Milly.

“To Carter’s Cats in Planters Plain,” he replied.

“Where is Patty Perry?” asked Detective Denny.

“She had to catch a train,” said the man.

“Hmmm,” thought Denny. “Cody’s full name is Cody Carter. Sounds like Carter’s Cats! And he’s on a train to Planters Plain.”

Denny figured Patty would sell the cats and then Cody would steal them back. Only this time, Patty made the snatch. “They resell the cats in Planters Plain,” he realized, “and split the money!”

“Sounds illegal!” said the man with the van.

The Planters Plain police met the train and took the catnappers straight to jail. Best of all, the cats in captivity, including Milly’s Mousie, were returned to their owners.