The U.S. should do one of two things to avoid the ongoing coronavirus epidemic, which is currently spreading at a pace of about 60,000 new cases every day.
Whether it can absolutely lock everyone down — or it can continually check people out.
The lockdown strategy works because if infected people aren’t able to get close to non-infected people, the transmission chain is broken even though we don’t know who is actually infected.
The research strategy works as it helps us to classify infected individuals and separate them from uninfected individuals without causing anyone else to stay home.However, the problem with lockdowns is that Americans have zero appetite for even targeted, localized sequels after having endured a big national this spring — and suffering the economic fallout with little to show for it.That leaves it to the test.
The latest data, unfortunately, shows that testing is falling across much of the USA. According to Johns Hopkins University, over the past week in 30 states — more than half the country — the average number of COVID-19 tests per 1,000 people is down. Nationally, the total number of daily tests fell in the same timeframe by 8.75 percent, from 822.470 on July 29 to 750.517 on Aug 4.And while Hurricane Isaias has affected a few of the states where testing slipped, most have not. Most are states — 22 in all — where a high percentage of COVID-19 tests still return positive, indicating that they don’t cast a broad enough net to track (and control) their outbreaks.In short, while President Trump is right that the U.S. has performed more tests than any other country, despite the magnitude of its epidemic, it’s not testing enough. And the testing that it is doing is not helping as much as it should, for reasons we will explain.The good news is that a simple solution might come in: new measures that emphasize speed over sensitivity.Storms aside, the key reason U.S. research is going down rather than up is that the type of testing we are doing — PCR (polymerase chain reaction)—appears to have reached its limit. PCR tests are the gold standard for COVID-19 diagnosis, and understandably so: more than 98 percent of positive cases are correctly detected.But they are sluggish too, and they’re getting slower. As the virus spreads, more and more potentially exposed Americans are demanding tests, forcing exhausted U.S. laboratories to fight for the resources needed to process so many samples in other countries. Laboratories frequently run out. As a result, crippling backlogs have delayed the test results for so long that they have become essentially worthless.
According to a new national survey conducted by researchers from Harvard University, Northeastern University, Northwestern University and Rutgers University, in July, Americans tested for COVID-19 reported waiting for their results on average for four days. Approximately 10 per cent reported waiting 10 days or more.
Yet experts in the field of public health claim findings that take more than 24 to 48 hours to defeat the test intention. By the time people get a good outcome, some may already have been compromised. They may have been contaminated by others by the time they receive a negative result.
Americans tend to get the message. “Long waiting times and long turnaround times means people just give up,” tweeted Tuesday Dr Ashish Jha, director of the Harvard Global Health Institute.
For short, the failure of U.S. assessments has revealed the fatal flaw. Costly and inefficient PCR testing is good when an outbreak is fairly modest; in that scenario, you can afford to invest in a slower, labor intensive test that won’t miss any positive cases if you want to stop the virus from spreading until it’s too late.But when it’s already too late — when more than 4.8 million infections were reported and nearly 160,000 people died — the PCR infrastructure can not keep up.Imagine a $1, paper-based at-home test which is as easy to distribute and use as a pregnancy test. Imagine waking up in the morning, applying saliva or mucus to a tube of chemicals, waiting for 15 minutes, dipping a strip of paper into the tube and reading the results — immediately.Imagine every single person doing this in America now every few days.So-called quick detection of antigens is not science fiction. They do exist already, in fact. Two such tests, conducted by BD and Quidel, have received Food and Drug Administration emergency authorization, although both still require to run instruments. (This week, the governors of six states declared a joint tender to buy a total of 3.5 million of these antigen tests.)Another $1 antigen test has been put to use in Senegal. And U.S. companies such as E25Bio and Sherlock Biosciences have developed at-home tests as cheap and easy as the one described above.These are not the same as the antibody tests you may have heard of, which measure virus-fighting substances in the blood of people who have previously been infected (and thus may have immunity). Rapid antigen testing is intended to detect chronic, active infections.But why is it that the U.S. government will not mass-produce antigen tests and openly distribute them to everyone? Thus far, the big challenge has been what news stories prefer to define as “exactness,” but “sensitivity” is a better way of thinking about it.
PCR tests produce thousands of copies of the RNA of the virus, and can therefore detect it at very low rates. Antigen tests rely on a molecule that binds to protein spikes of the coronavirus; at very low rates of infection, the sputum sample can not contain enough viral particles to cause a positive result.The fear is that we’ll miss a lot of cases if we focus on antigen tests. But that fear may be unfounded for two reasons.The first is we are missing tons of cases already. Our current PCR program checks just enough people to detect around 10 per cent of the total number of infections, according to CDC antibody results. “We would still identify 50 percent of all current infections in the country if everyone took an antigen test today — even identifying only 50 percent of the positive ones —,” Jha explained.That’s “five times more than the 10 percent of cases we ‘re actually finding at the moment because we’re studying so few individuals.”The second is that in the early days of infection the amount of coronavirus in the body increases exponential. At first, no test would be sensible enough to detect it during the incubation period. A PCR check will pick it up about three to five days later. According to Mina a rapid antigen test will give a positive result after another eight to 24 hours.And the problem is not, can an antigen check detect an infection? When it is. This distinguishes crucially. Say the PCR test delivers a positive on day four, and on day five the antigen test produces a positive. As best it can be said by experts, when people can transmit the virus to others, both day four and day five are before or near the start of the window.But if the person taking the PCR test does not find out if he or she is positive until day eight, or even day 14, while the person taking the antigen test finds out on day five, the antigen test is far more useful in stopping the spread of the virus, even if it is less sensitive.What if your viral load on day five was too low to detect it for the antigen test? Your infection would probably still not be very transmissible. Then the next test that you take would pick it up on day seven. And the person who was taking the PCR test will still not get the results.”The vast majority of PCR positive tests that we are currently obtaining in this country are still detecting people long after they stop being contagious,” Mina explained recently. “What we’re doing with all of this testing is blocking the testing infrastructure, and basically finding people we can’t even act for because they’re transmitting.”
Current FDA guidelines stipulate that almost as well as a PCR test must be performed in any new coronavirus test vying for emergency clearance. But as fall approaches — and with it the colder weather, increased indoor activity, a return to school and the potential for even bigger waves of infection — the time may have come to rethink those regulations.Rapid antigen testing is having its challenges. Fair distribution on a mass scale would probably require billions of dollars in government investment; cheap and easy at-home tests would only work if they were conscientiously taken by everyone. Yet experts say it makes more sense than the status quo.
“If you had asked me this a few months ago, I would have said that we just need to do the PCR tests,” Susan Butler-Wu, a clinical microbiologist at Southern California University, told the New York Times Wednesday. “But we have gone so far in this country. This is a tragedy. It’s time for sink in the kitchen.
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