Deadly virus approaches tigers

India’s most important tiger conservation body is to investigate growing concern that Asia’s wild tigers are 【小题1】 to a deadly new disease.

The National Tiger Conservation Authority is to fun d a study of Canine Distemper Virus(CDV) in six of the most important areas for the species, which could confirm a problem that a few experts have 【小题2】for a number of years.

There have been 【小题3】of CDV in wild tigers in other areas. According to Dr Dale Miquelle of the Wildlife Conservation Society, quite a few tigers were either killed or seriously affected by a disease that was probably CDV in 2010. And the Sikhote-Alin Biosphere Reserve has also reported a(n) 【小题4】 decline in tiger numbers.

CDV may also exist in the tiger population in Sumatra, where animals have been reported to be behaving 【小题5】and losing their fear of humans.

Dr John Lewis of the British charity Wildlife Vets International is helping the Sumatran【小题6】to fight the risk by training local vets in what he calls “the world’s first tiger- disease monitoring program”.

Lewis also believes that the way CDV changes tigers’ behavior could be a factor where tiger- human 【小题7】are an issue. This could be true of the Sundarbans, a large area shared by India and Bangladesh where man-eating is spreading.

Perhaps we should not be surprised that tigers are 【小题8】with CDV. In 2004, it killed 1,000 lions in the Serengeti in Tanzania, and as wildlife reserves are【小题9】surrounded by people with dogs, the problem is only likely to get worse.

But as Miquelle told BBC Wildlife, “Very few people were aware of the potential threat, let alone looking for it, even if it is 【小题10】in the system. But at least now they are.”

Like AIDS, flu is caused by a virus, a tiny packet of genes in a protein coat so simple that most biologists don’t 【小题1】 viruses truly “alive” until they invade（入侵）a host cell. Then they hijack the cell and use its energy to 【小题2】 out 100,000 to 1 million copies of themselves in just 10 hours. Eventually they become so great in number that they 【小题3】 the cell from within, flooding out to further infect the body. They are spread from respiratory（呼吸的）passages, through the cough and sneeze droplets on doorknobs, desktops, coat sleeves and food tables.

The cause of flu was unknown for many years—the virus wasn’t isolated until 1933. But now we know what makes flu such an annual irritant, and so 【小题4】 deadly, is that like HIV that causes AIDS, it is moving 【小题5】. Made of RNA instead of the more stable DNA, it changes like a movie monster, making vaccinations（疫苗接种）useless in a year or so.

One thing we know about the flu is that we can’t predict it. In part that’s because occasionally the flu will change completely in what is called a “shift” and 【小题6】 humans by such a surprise that a pandemic（流行疾病）breaks out. An estimated three to six shifts occurred in the 18th century, four in the 19th, and three in the 20th, the 1918 pandemic, the 1957 Asian flu and the 1968 Hong Kong flue. Because it can take six to nine months to make enough of an effective vaccine, a deadly shift that 【小题7】 around the world is what gives health authorities nightmares.

But there is a global network to try to stop such a pandemic in its tracks. More than 80 countries and 121 U.S. cities belong to a reporting system to 【小题8】 flu.

And now, doctors know what causes flu. They have decades of experience with vaccines to fight it, and they even have anti-viral drugs, though those are expensive and of limited 【小题9】.

A tiger at the Bronx Zoo in New York City has tested positive for the respiratory disease caused by the novel coronavirus, becoming the first known case of human-animal 【小题1】, the zoo's chief veterinarian said on Sunday.

Nadia, the 4-year-old Malayan tiger that tested positive, was 【小题2】 for the COVID-19 disease after 【小题3】 a dry cough along with three other tigers and three lions, the Wildlife Conservation Society, which manages the zoo, said in a statement.

All of the cats are expected to recover, it said. But officials believe this is a unique case because Nadia became sick after 【小题4】 to an asymptomatic zoo employee, Paul Calle, chief veterinarian at the Bronx Zoo, told Reuters.

Calle said they did not know which employee infected the tiger. "This is the first time that we have discovered that a person infects the animal and the animal gets sick," Calle said, adding that they planned to share the findings with other zoos and institutions. " I guess 【小题5】 we will all have a better understanding as a result.

While the other tigers and lions were also 【小题6】 symptoms, the zoo decided to test only Nadia because she was the sickest and   had started to lose her appetite already, and they did not want to 【小题7】 all the cats to anesthesia(麻醉), Calle said.

Nadia 【小题8】 X-rays, an ultrasound(超声波) and blood tests to try to figure out what was making her sick . They decided to test for COVID-19 【小题9】 the surge in cases in New York City, the epicenter of the outbreak in the United States.The first tiger at the zoo, which has been shut since mid-March, began showing 【小题10】 of illness on March 27, according to the US Department of Agriculture National Veterinary Services Laboratories.