Translator notes:Almost every country can't survive the outbreak of the global epidemic, and the United States has completed the "counter attack" in a short time, becoming the country with the largest number of confirmed cases in the world. But with the development of time, the epidemic situation in the United States seems to be stable, and there is no surge. Has the United States managed to contain the outbreak? The latest statistics may help us find the answer.
How many people are infected with coronavirus in the United States? This is one of the most difficult questions Americans want to know.
More than two months after the outbreak, the problem remains puzzling. In the covid-19 tracking program (CTP) organized by Atlantic Monthly, more than 100 volunteers and experts made statistics one by one in each state of the United States. As of April 15, at least 630000 people in the United States had been diagnosed with covid-19. But there is plenty of evidence that the figure is underestimated.
Underrated American patient population
Every time some ordinary people test, at least some infected people will be diagnosed. And, as ProPublica website initially reported, the number of deaths at home across the country has soared. and these people may die without access to the medical system COVID-19, which means they have never been examined and have not been counted.
Obviously, some Americans are infected with coronavirus, but they are not in official data. And now, with a newly reliable statistic —— positive rates, we can estimate the size of the group and uncover the true face of the iceberg.
The positive rate is close to 20%? It may not be true!
According to the CTP tracking program, nearly one in five people tested for coronavirus in the United States have been found to be infected with the virus. In other words, the U.S. test has a positive rate of nearly 20%.
Data of covid-19 positive patients in the United States as of April 15
Jason Andrews, professor of infectious diseases at Stanford University, told us that the number was "very high ". Such a high positive rate almost means that doctors only test people with very high risk of infection. People with milder symptoms and those without symptoms were not tested and counted. In countries with extensive testing, those who are not infected should be far more than those who are infected, so their positive rates are low.
In terms of prevalence, the positive rate is not the same as the proportion of covid-19 cases in the overall population of the United States. Although the United States is trying to get more accurate numbers from blood tests, no one knows the real number of Americans who are exposed to or infected with the coronavirus. The prevalence rate is a crucial figure for epidemiologists, in part because it allows experts to calculate the true infection death rate of pathogens.
However, the positive rate is still valuable. "It's not a normal indicator, but in some cases it can be very useful," Andrews said. Positive rates are often used to track the spread of rare and deadly diseases, such as malaria, where most people cannot detect them. If the same proportion of people are tested over a period of time, the positive rate can even be used to calculate the infectivity of a disease. "
The positive rate can be used as an indicator of the severity of the outbreak
Because the number of people tested for covid-19 has changed over time, the U.S. positive rate does not yet provide detailed information on the infectious or lethal rate of the disease. But we can still use this statistic to get a general idea of the severity of the epidemic in different regions, Andrews said. For example, one country has a positive rate of 25%, the other has a positive rate of 2%, which is obviously better.
The 20% positive rate in the United States is very disturbing. In the United States, the number of covid-19 tests on April 15 was almost 25 times that on March 15, but the daily positive rate and the overall positive rate increased in the same month. If the epidemic is indeed under control, the proportion of positive rate will be less and less as the number of tests increases. But sadly, so far that hasn't happened.
Detection mechanism driven by epidemic situation
Experts said that before the end of the blockade in the United States, in an ideal testing system, or any testing system must be done, anyone with fever and dry cough should be tested immediately. Even if not all novel coronavirus is likely to be infected by a large number of people, because humans are also prone to infection with many other respiratory diseases. However, when only patients with severe symptoms can be tested, it will cause a high positive rate.
Local rationing is not the only reason why Americans can't be tested. Some people live in a place where they don't do tests at all. Either the doctor's office doesn't have tests, or the local medical system is very strained, or there is no medical institution at all. Others are reluctant to see a doctor, or are never serious enough to be tested. But if the United States tests more people, as experts say, then crowd monitoring or workplace testing can also find infected people.
The test positive rate in the United States is second only to that in the United Kingdom
The test positive rate clearly shows that the United States is still far behind other countries in the process of fighting the epidemic. South Korea and the United States found the first case of coronavirus on the same day. South Korea has detected more than 500000 people, accounting for about 1% of the total population, and found about 10500 cases. The United States has tested 3.2 million people, or 1% of the population, but it has found more than 630000 cases. As a result, the positive rate in the United States is 20%, while that in South Korea is only about 2%, a whole order of magnitude lower than that in the United States.
South Korea, the first confirmed patient on the same day, has contained the outbreak
South Korea is not the only country with a low positive rate, and the U.S. data "dwarfs" almost all other developed countries. The positive rates in Canada, Germany and Denmark range from 6% to 8%. The positive rates in Australia and New Zealand were 2%. Even in Italy, where the epidemic is most severe, the positive rate is only 15%. In fact, the only rich country with a higher positive rate than the United States is the United Kingdom, where more than 30% of people are tested positive for the virus.
If you compare states in the United States with regions in other countries, the results are the same. In Lombardy, Italy's worst hit region, the current positive rate is about 28%, similar to that in Connecticut. But the worst hit state in the United States, New York, has a 41% positive rate. In New Jersey, it's shocking that one in two people tested for the virus was found to be carrying it.
The prevalence of covid-19 in the New York area may be higher than anywhere else in the United States, but five other states have more than 20 percent positive rates: Michigan, Georgia, Massachusetts, Illinois, and Colorado. They are all over the country, and there are obvious serious outbreaks. Each of the eight states with a positive rate of more than 20% reported more deaths than South Korea.
Meanwhile, Hawaii has twice as many people tested as Illinois, but its positive rate is only one tenth that of Illinois. Stanford University Professor Andrews said that as the epidemic gets under control, more states should have positive rates closer to Hawaii. At the start of the epidemic, he said, the number of actual infections and tests per day will surge. As the situation stabilizes, if the detection rate drops and the positive rate also drops, it is a sign that the epidemic is turning better. "
When will the epidemic stabilize? Some people are happy and others are worried!
Not every epidemiologist is as reassured by the results of the positive rate test as Andrews. "If you want to interpret positive rates as prevalence in a particular area, you have to assume that many other factors remain the same," said Daniel westerlech, a professor of epidemiology at the University of North Carolina He warned that it was not clear who had been tested and how reliable the tests were, and that it was not reliable to draw significant conclusions based on the positive rate alone.
"We haven't tested enough people yet, and if you randomize the entire population, we don't know what the results will be," he said. We don't know how many asymptomatic people are spreading the virus. " As a result, he suggested that great care should be taken when using positive rates, and claimed it was his job to be cautious about the data.
"We are confident that the current positive rate in the United States will decrease," westerlech said. First, because states and cities ration tests, it means that only those who are most seriously ill or vulnerable, such as residents of nursing homes, are tested. Secondly, although a variety of nose swab detection methods are being used all over the country, the PCR used is usually very reliable. "
Epidemic data are becoming more and more reliable
In the past few weeks, nationwide test positive data in the United States has gradually become more reliable. At the end of March, not all States will report all the results of commercial laboratories. Now, almost every state publishes these numbers.
Although the data of CTP project may not cover all coronavirus detection in the United States, the current evidence shows that the data of CTP project is quite complete. When the White House's coronavirus task force reported the number of tests completed across the country, its data was roughly the same as that of the CTP program. In addition, the top-level statistics released by quest and labcorp, the largest commercial test lab, are consistent with the data in the CPT tracking project.
Why is the U.S. epidemic data stable? The detection limit has been reached!
The high positive rate suggests that the number of new cases in the United States has stabilized only becauseThe detection capacity in the United States has reached the upper limit。 In terms of positive cases alone, while the number of confirmed cases in the United States is moving towards 650000 (as of April 15), the number of new cases per day seems to be stabilizing or even declining.
There are several ways to explain this change. For example, it may indicate that more than 3.2 million tests completed in the United States in the past two months have resulted in a large number of people actually infected. Although not all cases have been confirmed in the United States, the decline in new positive cases may indicate that the United States has begun to control the spread of the virus.
Another way to explain the decline in the number of new cases is that the number of tests completed each day has also stabilized. Since April 1, the United States has tested about 145000 people every day, without a steady upward trend. The number of new cases per day is closely related to the number of new tests per day.
Novel coronavirus pneumonia is also likely to be seen in the United States if the United States tests more people. Combined with such a high test positive rate, this indicates that there are still a large number of unknown and non statistical patients with covid-19 in the United States.
The tragedy of non critical medical treatment is unfolding in the United States
Every uncounted case is a small tragedy and a microcosm of the failure of the U.S. to test medical infrastructure. Sarah Pavis, a 36-year-old engineer in New York, called 911 when she woke up one day feeling her heart beat faster and her limbs numb. But it's nine days after COVID-19 symptoms.
New York has a staggering 55% positive rate, with more than 11000 residents diagnosed, but paves is not among them. When the ambulance arrived at Parvis's apartment, an emergency center worker said there was nothing he could do. He explained that hospitals in the city only receive patients with a blood oxygen content of 94% or less. Pavis had a blood oxygen reading of 96%. The 2% difference means that her condition is not serious enough to be hospitalized, tested or counted.
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