巴西和美国开始测试下水道，看新冠肺炎的严重程度。全文如下

Is It Safe to Come Out of Lockdown? Check the Sewer.

Wastewater could provide early, painless and localized data about the rise or fall of coronavirus levels.

The world is eager to come out of lockdown. But if countries simply return to business as usual, new outbreaks of Covid-19 will follow. The only solution that public health experts see is to keep careful track of the coronavirus and clamp down on new flare-ups.

The trouble is that the most obvious way to monitor the virus — testing person by person — has already proved to be a huge, expensive challenge. Experts say we’re nowhere near the scale we need to get a good picture of the pandemic.

Now some scientists are looking for the virus not in our noses, blood or spit, but somewhere else: in our sewers.

“It’s the signature of a whole community,” said Krista Wigginton, an environmental engineer at the University of Michigan who has been finding the coronavirus in wastewater around the Bay Area in California.

Water authorities and governments are in discussions with scientists and companies about tracking the pandemic through the detection of viruses in the sewer. Wastewater monitoring could provide early warnings of outbreaks. It could potentially give governments some of the data they need about when to end lockdowns and when to ratchet them back up.

Measuring viruses in wastewater in effect tests an entire city or region at once. While only some people may get tested for the coronavirus on a given day, everyone uses the toilet.

“It’s a great leveler,” said Christobel Ferguson, chief innovation officer of the Water Research Foundation.

This week, the foundation sponsored a virtual research summit, during which Dr. Wigginton and other experts shared their early results and developed a road map for improving their surveillance.

For decades, public health workers have looked in sewage for signs of viral outbreaks. The World Health Organization has monitored polio viruses this way, to assess how well its vaccination campaigns have worked.

In the early days, researchers had to run painstaking tests to find viruses in wastewater. They had to mix the water with cells so that the viruses could infect them. Then the researchers had to wait for the new viruses to emerge.

Later, researchers were able to skip these experiments. They could simply fish out genetic material from the water, read its sequence, and determine what kind of virus they were dealing with. Even newer technology has made it possible to estimate the number of viruses by counting up the viral genes in a water sample.