VOA慢速英语--废水检测可以确定医院和学校的疫情情况（在线收听）

Wastewater Testing Could Identify Outbreaks at Hospitals, Schools

Researchers have launched several projects to test coronavirus levels at hospitals and schools to identify new outbreaks.

The new projects are using similar sewage testing methods that some cities and countries around the world have already used. Earlier efforts centered on wastewater tests in order to follow the progression of the coronavirus over large population areas. But the new programs aim to test sewage from single buildings, such as hospitals, schools and care centers.

The coronavirus is mainly spread through small drops coming from an infected person's mouth and nose. But studies have shown that it can also be released through human waste.

The researchers say testing wastewater can help identify where the virus is spreading and reduce the need for mass testing. The collection and examination of sewage from buildings costs much less than testing hundreds of individual people.

Wastewater tests can also be carried out often and quickly. With infection rates rising again in much of the world, it is especially important for schools, hospitals and care centers to be able to catch new cases early.

Francis Hassard is an expert in public health microbiology with Britain's Cranfield University. "What we're trying to do is identify outbreaks before they happen," he told the Reuters news agency.

Hassard is helping lead a project that started collecting samples at 20 secondary schools in London last month. The team, which is financed by the British government, plans to expand its sampling to at least 70 schools. The effort is currently still a research project aimed at testing the system's methods.

In Canada, researchers at the University of Calgary have been gathering samples from three local hospitals, including one that experienced a recent outbreak that killed 12 people. The team was still working to improve its methods when the outbreak happened.

When researchers went back to test wastewater, they found the amount of coronavirus genetic material had jumped 580 percent as the virus spread, said Kevin Frankowski. He is director of the university's Advancing Canadian Wastewater Assets project.

"We saw a very significant change," Frankowski said. "It was really strong proof that this ... (method) works."

The project shares data with Alberta Health Services, which runs a large number of hospitals. Frankowski said that if levels show a sharp rise again, hospital officials could immediately start testing individuals or take other steps to limit the spread.

In the United States, the professional services company GHD has set up wastewater testing at several university housing buildings. It also started advertising the service to long-term care homes. The service has already received interest, GHD's Peter Capponi told Reuters.

So far, most of the world's wastewater testing for coronavirus has been completed at sewage treatment plants. But it can take 24 to 36 hours for waste to arrive at a treatment plant. And heavy rain or industrial runoff can dilute samples.

When virus levels rise at a treatment plant, it is not always clear what actions officials should take. But when virus material suddenly appears in sewage leaving a single building, the next steps are more clear.

At the University of Arizona, for example, sewage from one student tested positive for coronavirus on August 25. The next day, the university began testing students. Two tested positive and were immediately isolated, the school said. University officials said the early action may have prevented a severe outbreak.

Words in This Story

outbreak – n. a sudden start or increase of fighting or disease

sewage – n. wastewater and human waste products

sample – n. a small amount of something that represents what it is like

significant – adj. important or noticeable

dilute – v. to make a liquid thinner or weaker by adding water or another liquid to it

positive – adj. in a medical test, positive means the person being tested has a disease or condition

isolate – v. to put or keep (someone or something) in a place or situation that is separate from others